diff --git a/src/Cargo.lock b/src/Cargo.lock
index d4544ffa3244f..9a3467e762215 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -1,3 +1,17 @@
+[[package]]
+name = "addr2line"
+version = "0.6.0"
+source = "git+https://github.com/est31/addr2line?branch=no_std_prototype#19fca3a5af2f4814444f07ca8199080d2f94a38d"
+dependencies = [
+ "cpp_demangle 0.2.9 (git+https://github.com/gimli-rs/cpp_demangle?rev=6d5320d2f5c119923647b6d7d2a7d563717a4ddf)",
+ "fallible-iterator 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gimli 0.16.0 (git+https://github.com/est31/gimli?rev=304caacf8b73f117813b1a0d436ce24403459bf2)",
+ "intervaltree 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazycell 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "object 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "0.6.4"
@@ -21,8 +35,6 @@ version = "0.0.0"
 dependencies = [
  "build_helper 0.1.0",
  "cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
  "libc 0.0.0",
 ]
 
@@ -30,8 +42,6 @@ dependencies = [
 name = "alloc_system"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
  "dlmalloc 0.0.0",
  "libc 0.0.0",
 ]
@@ -470,6 +480,14 @@ name = "core-foundation-sys"
 version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "cpp_demangle"
+version = "0.2.9"
+source = "git+https://github.com/gimli-rs/cpp_demangle?rev=6d5320d2f5c119923647b6d7d2a7d563717a4ddf#6d5320d2f5c119923647b6d7d2a7d563717a4ddf"
+dependencies = [
+ "glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "crates-io"
 version = "0.17.0"
@@ -598,10 +616,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "dlmalloc"
 version = "0.0.0"
-dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
-]
 
 [[package]]
 name = "dtoa"
@@ -699,6 +713,11 @@ dependencies = [
  "synstructure 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "fallible-iterator"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "features"
 version = "0.1.0"
@@ -809,6 +828,17 @@ name = "getopts"
 version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "gimli"
+version = "0.16.0"
+source = "git+https://github.com/est31/gimli?rev=304caacf8b73f117813b1a0d436ce24403459bf2#304caacf8b73f117813b1a0d436ce24403459bf2"
+dependencies = [
+ "arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "byteorder 1.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fallible-iterator 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "stable_deref_trait 1.0.0 (git+https://github.com/kevinaboos/stable_deref_trait?rev=8aa58b57a20b0dc215084f84de81e0f7e7dea76e)",
+]
+
 [[package]]
 name = "git2"
 version = "0.7.1"
@@ -851,6 +881,16 @@ dependencies = [
  "regex 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "goblin"
+version = "0.0.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "plain 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "scroll 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "graphviz"
 version = "0.0.0"
@@ -964,6 +1004,14 @@ dependencies = [
  "xz2 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "intervaltree"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "smallvec 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "is-match"
 version = "0.1.0"
@@ -1057,13 +1105,14 @@ name = "lazycell"
 version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "lazycell"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "libc"
 version = "0.0.0"
-dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
-]
 
 [[package]]
 name = "libc"
@@ -1300,6 +1349,16 @@ dependencies = [
  "libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "object"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "goblin 0.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "scroll 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "uuid 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "open"
 version = "1.2.1"
@@ -1350,8 +1409,6 @@ dependencies = [
 name = "panic_abort"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
  "libc 0.0.0",
 ]
 
@@ -1359,9 +1416,6 @@ dependencies = [
 name = "panic_unwind"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
  "libc 0.0.0",
  "unwind 0.0.0",
 ]
@@ -1454,6 +1508,11 @@ name = "pkg-config"
 version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "plain"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "polonius-engine"
 version = "0.5.0"
@@ -1486,6 +1545,14 @@ dependencies = [
  "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "proc-macro2"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "proc_macro"
 version = "0.0.0"
@@ -1501,8 +1568,6 @@ name = "profiler_builtins"
 version = "0.0.0"
 dependencies = [
  "cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
 ]
 
 [[package]]
@@ -1537,6 +1602,14 @@ dependencies = [
  "proc-macro2 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "quote"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "racer"
 version = "2.0.14"
@@ -2054,12 +2127,9 @@ dependencies = [
 name = "rustc_asan"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
  "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
 ]
 
 [[package]]
@@ -2080,30 +2150,10 @@ dependencies = [
 name = "rustc_codegen_llvm"
 version = "0.0.0"
 dependencies = [
- "bitflags 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "flate2 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "jobserver 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc 0.0.0",
  "rustc-demangle 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc_allocator 0.0.0",
- "rustc_apfloat 0.0.0",
- "rustc_codegen_utils 0.0.0",
- "rustc_data_structures 0.0.0",
- "rustc_errors 0.0.0",
- "rustc_incremental 0.0.0",
  "rustc_llvm 0.0.0",
- "rustc_mir 0.0.0",
- "rustc_platform_intrinsics 0.0.0",
- "rustc_target 0.0.0",
- "serialize 0.0.0",
- "syntax 0.0.0",
- "syntax_pos 0.0.0",
- "tempdir 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2224,23 +2274,17 @@ dependencies = [
 name = "rustc_llvm"
 version = "0.0.0"
 dependencies = [
- "bitflags 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "build_helper 0.1.0",
  "cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc_cratesio_shim 0.0.0",
 ]
 
 [[package]]
 name = "rustc_lsan"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
  "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
 ]
 
 [[package]]
@@ -2286,12 +2330,9 @@ dependencies = [
 name = "rustc_msan"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
  "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
 ]
 
 [[package]]
@@ -2390,12 +2431,9 @@ dependencies = [
 name = "rustc_tsan"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
  "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
 ]
 
 [[package]]
@@ -2531,6 +2569,24 @@ name = "scopeguard"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "scroll"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "scroll_derive 0.9.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "scroll_derive"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.14.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "semver"
 version = "0.9.0"
@@ -2608,6 +2664,11 @@ name = "siphasher"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "smallvec"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "smallvec"
 version = "0.6.0"
@@ -2623,6 +2684,11 @@ dependencies = [
  "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "stable_deref_trait"
+version = "1.0.0"
+source = "git+https://github.com/kevinaboos/stable_deref_trait?rev=8aa58b57a20b0dc215084f84de81e0f7e7dea76e#8aa58b57a20b0dc215084f84de81e0f7e7dea76e"
+
 [[package]]
 name = "stable_deref_trait"
 version = "1.0.0"
@@ -2632,14 +2698,14 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "std"
 version = "0.0.0"
 dependencies = [
- "alloc 0.0.0",
+ "addr2line 0.6.0 (git+https://github.com/est31/addr2line?branch=no_std_prototype)",
  "alloc_jemalloc 0.0.0",
  "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cc 1.0.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.0.0",
- "core 0.0.0",
+ "gimli 0.16.0 (git+https://github.com/est31/gimli?rev=304caacf8b73f117813b1a0d436ce24403459bf2)",
  "libc 0.0.0",
+ "object 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "panic_abort 0.0.0",
  "panic_unwind 0.0.0",
  "profiler_builtins 0.0.0",
@@ -2648,7 +2714,6 @@ dependencies = [
  "rustc_lsan 0.0.0",
  "rustc_msan 0.0.0",
  "rustc_tsan 0.0.0",
- "std_unicode 0.0.0",
  "unwind 0.0.0",
 ]
 
@@ -2729,6 +2794,16 @@ dependencies = [
  "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "syn"
+version = "0.14.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "synom"
 version = "0.11.3"
@@ -3037,8 +3112,6 @@ dependencies = [
 name = "unwind"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
  "libc 0.0.0",
 ]
 
@@ -3080,6 +3153,14 @@ name = "utf8-ranges"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "uuid"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "vcpkg"
 version = "0.2.3"
@@ -3167,6 +3248,7 @@ version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [metadata]
+"checksum addr2line 0.6.0 (git+https://github.com/est31/addr2line?branch=no_std_prototype)" = "<none>"
 "checksum aho-corasick 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d6531d44de723825aa81398a6415283229725a00fa30713812ab9323faa82fc4"
 "checksum ammonia 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fd4c682378117e4186a492b2252b9537990e1617f44aed9788b9a1149de45477"
 "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
@@ -3196,6 +3278,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum compiletest_rs 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "608d9d3ccc45b63bf337d2ff5e65def5a5a52c187122232509f6b72707f61b1b"
 "checksum core-foundation 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c7caa6cb9e76ddddbea09a03266d6b3bc98cd41e9fb9b017c473e7cca593ec25"
 "checksum core-foundation-sys 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b2a53cce0ddcf7e7e1f998738d757d5a3bf08bf799a180e50ebe50d298f52f5a"
+"checksum cpp_demangle 0.2.9 (git+https://github.com/gimli-rs/cpp_demangle?rev=6d5320d2f5c119923647b6d7d2a7d563717a4ddf)" = "<none>"
 "checksum crossbeam 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "24ce9782d4d5c53674646a6a4c1863a21a8fc0cb649b3c94dfc16e45071dea19"
 "checksum crossbeam-deque 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f739f8c5363aca78cfb059edf753d8f0d36908c348f3d8d1503f03d8b75d9cf3"
 "checksum crossbeam-epoch 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "927121f5407de9956180ff5e936fe3cf4324279280001cd56b669d28ee7e9150"
@@ -3219,6 +3302,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum error-chain 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ff511d5dc435d703f4971bc399647c9bc38e20cb41452e3b9feb4765419ed3f3"
 "checksum failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "934799b6c1de475a012a02dab0ace1ace43789ee4b99bcfbf1a2e3e8ced5de82"
 "checksum failure_derive 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c7cdda555bb90c9bb67a3b670a0f42de8e73f5981524123ad8578aafec8ddb8b"
+"checksum fallible-iterator 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d6034a9c9dfce417c7710128d202eef406878cd2fe294e76e2ee05259c9b042d"
 "checksum filetime 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)" = "714653f3e34871534de23771ac7b26e999651a0a228f47beb324dfdf1dd4b10f"
 "checksum filetime 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "08530a39af0bd442c40aabb9e854f442a83bd2403feb1ed58fbe982dec2385f3"
 "checksum fixedbitset 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "86d4de0081402f5e88cdac65c8dcdcc73118c1a7a465e2a05f0da05843a8ea33"
@@ -3232,10 +3316,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum futf 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "51f93f3de6ba1794dcd5810b3546d004600a59a98266487c8407bc4b24e398f3"
 "checksum futures 0.1.20 (registry+https://github.com/rust-lang/crates.io-index)" = "0c5a3176836efa0b37f0e321b86672dfada1564aeb516fbed67b7c24050a0263"
 "checksum getopts 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)" = "b900c08c1939860ce8b54dc6a89e26e00c04c380fd0e09796799bd7f12861e05"
+"checksum gimli 0.16.0 (git+https://github.com/est31/gimli?rev=304caacf8b73f117813b1a0d436ce24403459bf2)" = "<none>"
 "checksum git2 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0f41c0035c37ec11ed3f1e1946a76070b0c740393687e9a9c7612f6a709036b3"
 "checksum git2-curl 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b502f6b1b467957403d168f0039e0c46fa6a1220efa2adaef25d5b267b5fe024"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
 "checksum globset 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1e96ab92362c06811385ae9a34d2698e8a1160745e0c78fbb434a44c8de3fabc"
+"checksum goblin 0.0.15 (registry+https://github.com/rust-lang/crates.io-index)" = "5e3ba9fec4dc9a09553388bff2724d3bf06bd64013539f2d3e1e3838eefb310a"
 "checksum handlebars 0.32.0 (registry+https://github.com/rust-lang/crates.io-index)" = "07af2ff31f66f39a5c8b8b8a5dc02734a453110146763e3a2323f4931a915a76"
 "checksum hex 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "459d3cf58137bb02ad4adeef5036377ff59f066dbb82517b7192e3a5462a2abc"
 "checksum home 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "8f94f6fbdc000a6eba0c8cf08632b2091bb59141d36ac321a2a96d6365e5e4dc"
@@ -3244,6 +3330,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum idna 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "014b298351066f1512874135335d62a789ffe78a9974f94b43ed5621951eaf7d"
 "checksum if_chain 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "61bb90bdd39e3af69b0172dfc6130f6cd6332bf040fbb9bdd4401d37adbd48b8"
 "checksum ignore 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "245bea0ba52531a3739cb8ba99f8689eda13d7faf8c36b6a73ce4421aab42588"
+"checksum intervaltree 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "586949c609276837d70c776c30afa5bbd374c55fe69b4e10261c6f595dc7b31a"
 "checksum is-match 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7e5b386aef33a1c677be65237cb9d32c3f3ef56bd035949710c4bb13083eb053"
 "checksum isatty 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "6c324313540cd4d7ba008d43dc6606a32a5579f13cc17b2804c13096f0a5c522"
 "checksum itertools 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)" = "f58856976b776fedd95533137617a02fb25719f40e7d9b01c7043cd65474f450"
@@ -3256,6 +3343,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum lazy_static 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "76f033c7ad61445c5b347c7382dd1237847eb1bce590fe50365dcb33d546be73"
 "checksum lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c8f31047daa365f19be14b47c29df4f7c3b581832407daabe6ae77397619237d"
 "checksum lazycell 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a6f08839bc70ef4a3fe1d566d5350f519c5912ea86be0df1740a7d247c7fc0ef"
+"checksum lazycell 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d33a48d0365c96081958cc663eef834975cb1e8d8bea3378513fc72bdbf11e50"
 "checksum libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)" = "6fd41f331ac7c5b8ac259b8bf82c75c0fb2e469bbf37d2becbba9a6a2221965b"
 "checksum libgit2-sys 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1ecbd6428006c321c29b6c8a895f0d90152f1cf4fd8faab69fc436a3d9594f63"
 "checksum libssh2-sys 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0db4ec23611747ef772db1c4d650f8bd762f07b461727ec998f953c614024b75"
@@ -3280,6 +3368,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum num-traits 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)" = "92e5113e9fd4cc14ded8e499429f396a20f98c772a47cc8622a736e1ec843c31"
 "checksum num-traits 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "dee092fcdf725aee04dd7da1d21debff559237d49ef1cb3e69bcb8ece44c7364"
 "checksum num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c51a3322e4bca9d212ad9a158a02abc6934d005490c054a2778df73a70aa0a30"
+"checksum object 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9d516d9e7232a46e709ab9027f51e2d3ce97608bce167df6badf12b258a6a61b"
 "checksum open 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c281318d992e4432cfa799969467003d05921582a7489a8325e37f8a450d5113"
 "checksum openssl 0.10.6 (registry+https://github.com/rust-lang/crates.io-index)" = "63246f69962e8d5ef865f82a65241d6483c8a2905a1801e2f7feb5d187d51320"
 "checksum openssl-probe 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
@@ -3297,15 +3386,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum phf_generator 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)" = "6b07ffcc532ccc85e3afc45865469bf5d9e4ef5bfcf9622e3cfe80c2d275ec03"
 "checksum phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)" = "07e24b0ca9643bdecd0632f2b3da6b1b89bbb0030e0b992afc1113b23a7bc2f2"
 "checksum pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "3a8b4c6b8165cd1a1cd4b9b120978131389f64bdaf456435caa41e630edba903"
+"checksum plain 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
 "checksum polonius-engine 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a5b6b0a7f5f4278b991ffd14abce1d01b013121ad297460237ef0a2f08d43201"
 "checksum precomputed-hash 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
 "checksum pretty_assertions 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a029430f0d744bc3d15dd474d591bed2402b645d024583082b9f63bb936dac6"
 "checksum proc-macro2 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "49b6a521dc81b643e9a51e0d1cf05df46d5a2f3c0280ea72bcb68276ba64a118"
+"checksum proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "effdb53b25cdad54f8f48843d67398f7ef2e14f12c1b4cb4effc549a6462a4d6"
 "checksum pulldown-cmark 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d6fdf85cda6cadfae5428a54661d431330b312bc767ddbc57adbedc24da66e32"
 "checksum quick-error 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "eda5fe9b71976e62bc81b781206aaa076401769b2143379d3eb2118388babac4"
 "checksum quine-mc_cluskey 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)" = "07589615d719a60c8dd8a4622e7946465dfef20d1a428f969e3443e7386d5f45"
 "checksum quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e920b65c65f10b2ae65c831a81a073a89edd28c7cce89475bff467ab4167a"
 "checksum quote 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7b0ff51282f28dc1b53fd154298feaa2e77c5ea0dba68e1fd8b03b72fbe13d2a"
+"checksum quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "e44651a0dc4cdd99f71c83b561e221f714912d11af1a4dff0631f923d53af035"
 "checksum racer 2.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "e713729f45f12df5c5e182d39506766f76c09133fb661d3622e0ddf8078911c2"
 "checksum radix_trie 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "03d0d770481e8af620ca61d3d304bf014f965d7f78e923dc58545e6a545070a9"
 "checksum rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)" = "15a732abf9d20f0ad8eeb6f909bf6868722d9a06e1e50802b6a70351f40b4eb1"
@@ -3353,6 +3445,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum schannel 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "85fd9df495640643ad2d00443b3d78aae69802ad488debab4f1dd52fc1806ade"
 "checksum scoped-tls 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8674d439c964889e2476f474a3bf198cc9e199e77499960893bac5de7e9218a4"
 "checksum scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "94258f53601af11e6a49f722422f6e3425c52b06245a5cf9bc09908b174f5e27"
+"checksum scroll 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "66f024a8cc5e456eb870f688dbd899c84f61190c82c7a911e40f926941969074"
+"checksum scroll_derive 0.9.4 (registry+https://github.com/rust-lang/crates.io-index)" = "f9a353f5dd99e42ff097d5a61db3257aa2c7127d76a3fa8287b642ef9ae0f7c5"
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum serde 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)" = "29465552c9b767d0cb44be3ddf4c3214be15d34975a7750f6cf4f409835f0248"
@@ -3363,8 +3457,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum shell-escape 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "170a13e64f2a51b77a45702ba77287f5c6829375b04a69cf2222acd17d0cfab9"
 "checksum shlex 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
 "checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
+"checksum smallvec 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "ee4f357e8cd37bf8822e1b964e96fd39e2cb5a0424f8aaa284ccaccc2162411c"
 "checksum smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "44db0ecb22921ef790d17ae13a3f6d15784183ff5f2a01aa32098c7498d2b4b9"
 "checksum socket2 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "ff606e0486e88f5fc6cfeb3966e434fb409abbc7a3ab495238f70a1ca97f789d"
+"checksum stable_deref_trait 1.0.0 (git+https://github.com/kevinaboos/stable_deref_trait?rev=8aa58b57a20b0dc215084f84de81e0f7e7dea76e)" = "<none>"
 "checksum stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "15132e0e364248108c5e2c02e3ab539be8d6f5d52a01ca9bbf27ed657316f02b"
 "checksum string_cache 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "39cb4173bcbd1319da31faa5468a7e3870683d7a237150b0b0aaafd546f6ad12"
 "checksum string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "479cde50c3539481f33906a387f2bd17c8e87cb848c35b6021d41fb81ff9b4d7"
@@ -3374,6 +3470,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum strum_macros 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0dd9bd569e88028750e3ae5c25616b8278ac16a8e61aba4339195c72396d49e1"
 "checksum syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)" = "d3b891b9015c88c576343b9b3e41c2c11a51c219ef067b264bd9c8aa9b441dad"
 "checksum syn 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)" = "91b52877572087400e83d24b9178488541e3d535259e04ff17a63df1e5ceff59"
+"checksum syn 0.14.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c67da57e61ebc7b7b6fff56bb34440ca3a83db037320b0507af4c10368deda7d"
 "checksum synom 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a393066ed9010ebaed60b9eafa373d4b1baac186dd7e008555b0f702b51945b6"
 "checksum synstructure 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a761d12e6d8dcb4dcf952a7a89b475e3a9d69e4a69307e01a470977642914bd"
 "checksum syntex_errors 0.52.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9e52bffe6202cfb67587784cf23e0ec5bf26d331eef4922a16d5c42e12aa1e9b"
@@ -3407,6 +3504,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum userenv-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "71d28ea36bbd9192d75bd9fa9b39f96ddb986eaee824adae5d53b6e51919b2f3"
 "checksum utf-8 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f1262dfab4c30d5cb7c07026be00ee343a6cf5027fdc0104a9160f354e5db75c"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
+"checksum uuid 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)" = "e1436e58182935dcd9ce0add9ea0b558e8a87befe01c1a301e6020aeb0876363"
 "checksum vcpkg 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "7ed0f6789c8a85ca41bbc1c9d175422116a9869bd1cf31bb08e1493ecce60380"
 "checksum vec_map 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "887b5b631c2ad01628bbbaa7dd4c869f80d3186688f8d0b6f58774fbe324988c"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
diff --git a/src/Cargo.toml b/src/Cargo.toml
index 8ce4c97601bab..c43ff9c19a2ab 100644
--- a/src/Cargo.toml
+++ b/src/Cargo.toml
@@ -1,6 +1,9 @@
 [workspace]
 members = [
   "bootstrap",
+  "libcore",
+  "libstd_unicode",
+  "liballoc",
   "rustc",
   "libstd",
   "libtest",
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index d482a0d565027..7a2aaa7e88469 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -729,7 +729,7 @@ impl<'a> Builder<'a> {
         } else {
             &self.config.channel
         };
-        cargo.env("__CARGO_DEFAULT_LIB_METADATA", &metadata);
+        cargo.env("__CARGO_DEFAULT_LIB_METADATA", &format!("{}-{}", metadata, mode.as_str()));
 
         let stage;
         if compiler.stage == 0 && self.local_rebuild {
@@ -838,7 +838,14 @@ impl<'a> Builder<'a> {
             // already-passed -C metadata flag with our own. Our rustc.rs
             // wrapper around the actual rustc will detect -C metadata being
             // passed and frob it with this extra string we're passing in.
-            cargo.env("RUSTC_METADATA_SUFFIX", "rustc");
+            let suffix = match mode {
+                Mode::Std => "rustc-std",
+                Mode::Test => "rustc-test",
+                Mode::Codegen => "rustc-codegen",
+                Mode::Rustc => "rustc-rustc",
+                Mode::ToolStd | Mode::ToolTest | Mode::ToolRustc => "rustc-tools",
+            };
+            cargo.env("RUSTC_METADATA_SUFFIX", suffix);
         }
 
         if let Some(x) = self.crt_static(target) {
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index b3ccb3cc3c926..5fe8443d7ea86 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -10,7 +10,8 @@
 
 //! Implementation of compiling the compiler and standard library, in "check" mode.
 
-use compile::{run_cargo, std_cargo, test_cargo, rustc_cargo, rustc_cargo_env, add_to_sysroot};
+use compile::{run_cargo, core_cargo, std_cargo, test_cargo,
+    rustc_cargo, rustc_cargo_env, add_to_sysroot};
 use builder::{RunConfig, Builder, ShouldRun, Step};
 use tool::{self, prepare_tool_cargo};
 use {Compiler, Mode};
@@ -43,17 +44,25 @@ impl Step for Std {
         let out_dir = builder.stage_out(compiler, Mode::Std);
         builder.clear_if_dirty(&out_dir, &builder.rustc(compiler));
 
-        let mut cargo = builder.cargo(compiler, Mode::Std, target, "check");
-        std_cargo(builder, &compiler, target, &mut cargo);
+        let mut core_cargo_invoc = builder.cargo(compiler, Mode::Std, target, "check");
+        core_cargo(builder, &compiler, target, &mut core_cargo_invoc);
+        let mut std_cargo_invoc = builder.cargo(compiler, Mode::Std, target, "check");
+        std_cargo(builder, &compiler, target, &mut std_cargo_invoc);
 
         let _folder = builder.fold_output(|| format!("stage{}-std", compiler.stage));
+        let libdir = builder.sysroot_libdir(compiler, target);
+
         println!("Checking std artifacts ({} -> {})", &compiler.host, target);
         run_cargo(builder,
-                  &mut cargo,
+                  &mut core_cargo_invoc,
+                  &libcore_stamp(builder, compiler, target),
+                  true);
+        add_to_sysroot(&builder, &libdir, &libcore_stamp(builder, compiler, target));
+        run_cargo(builder,
+                  &mut std_cargo_invoc,
                   &libstd_stamp(builder, compiler, target),
                   true);
 
-        let libdir = builder.sysroot_libdir(compiler, target);
         add_to_sysroot(&builder, &libdir, &libstd_stamp(builder, compiler, target));
     }
 }
@@ -88,6 +97,7 @@ impl Step for Rustc {
         let target = self.target;
 
         let stage_out = builder.stage_out(compiler, Mode::Rustc);
+        builder.clear_if_dirty(&stage_out, &libcore_stamp(builder, compiler, target));
         builder.clear_if_dirty(&stage_out, &libstd_stamp(builder, compiler, target));
         builder.clear_if_dirty(&stage_out, &libtest_stamp(builder, compiler, target));
 
@@ -176,6 +186,7 @@ impl Step for Test {
         let target = self.target;
 
         let out_dir = builder.stage_out(compiler, Mode::Test);
+        builder.clear_if_dirty(&out_dir, &libcore_stamp(builder, compiler, target));
         builder.clear_if_dirty(&out_dir, &libstd_stamp(builder, compiler, target));
 
         let mut cargo = builder.cargo(compiler, Mode::Test, target, "check");
@@ -242,6 +253,12 @@ impl Step for Rustdoc {
     }
 }
 
+/// Cargo's output path for the core library in a given stage, compiled
+/// by a particular compiler for the specified target.
+pub fn libcore_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
+    builder.cargo_out(compiler, Mode::Std, target).join(".libcore-check.stamp")
+}
+
 /// Cargo's output path for the standard library in a given stage, compiled
 /// by a particular compiler for the specified target.
 pub fn libstd_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 11d9154ba696c..4e5249343f25e 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -85,6 +85,12 @@ impl Step for Std {
                 copy_musl_third_party_objects(builder, target, &libdir);
             }
 
+            builder.ensure(CoreLink {
+                compiler: from,
+                target_compiler: compiler,
+                target,
+            });
+
             builder.ensure(StdLink {
                 compiler: from,
                 target_compiler: compiler,
@@ -100,22 +106,45 @@ impl Step for Std {
 
         let out_dir = builder.cargo_out(compiler, Mode::Std, target);
         builder.clear_if_dirty(&out_dir, &builder.rustc(compiler));
-        let mut cargo = builder.cargo(compiler, Mode::Std, target, "build");
-        std_cargo(builder, &compiler, target, &mut cargo);
+        let mut core_cargo_invoc = builder.cargo(compiler, Mode::Std, target, "build");
+        core_cargo(builder, &compiler, target, &mut core_cargo_invoc);
+        let std_cargo_invoc = if builder.no_std(target) != Some(true) {
+            let mut std_cargo_invoc = builder.cargo(compiler, Mode::Std, target, "build");
+            std_cargo(builder, &compiler, target, &mut std_cargo_invoc);
+            Some(std_cargo_invoc)
+        } else {
+            None
+        };
 
         let _folder = builder.fold_output(|| format!("stage{}-std", compiler.stage));
         builder.info(&format!("Building stage{} std artifacts ({} -> {})", compiler.stage,
                 &compiler.host, target));
         run_cargo(builder,
-                  &mut cargo,
-                  &libstd_stamp(builder, compiler, target),
+                  &mut core_cargo_invoc,
+                  &libcore_stamp(builder, compiler, target),
                   false);
-
-        builder.ensure(StdLink {
+        builder.ensure(CoreLink {
             compiler: builder.compiler(compiler.stage, builder.config.build),
             target_compiler: compiler,
             target,
         });
+        if let Some(mut std_cargo_invoc) = std_cargo_invoc {
+            run_cargo(builder,
+                      &mut std_cargo_invoc,
+                      &libstd_stamp(builder, compiler, target),
+                      false);
+            builder.ensure(StdLink {
+                compiler: builder.compiler(compiler.stage, builder.config.build),
+                target_compiler: compiler,
+                target,
+            });
+        }
+
+        builder.ensure(tool::CleanTools {
+            compiler,
+            target,
+            cause: Mode::Std,
+        });
     }
 }
 
@@ -133,68 +162,116 @@ fn copy_musl_third_party_objects(builder: &Builder,
     }
 }
 
+fn mac_os_deployment_env_var(cargo: &mut Command) {
+    if let Some(target) = env::var_os("MACOSX_STD_DEPLOYMENT_TARGET") {
+        cargo.env("MACOSX_DEPLOYMENT_TARGET", target);
+    }
+}
+
+/// Configure cargo to compile a few no_std crates like core,
+/// adding appropriate env vars and such.
+pub fn core_cargo(builder: &Builder,
+                  _compiler: &Compiler,
+                  _target: Interned<String>,
+                  cargo: &mut Command) {
+    mac_os_deployment_env_var(cargo);
+
+    // for no-std targets we only compile a few no_std crates
+    cargo.arg("--features").arg("c mem")
+        .args(&["-p", "alloc"])
+        .args(&["-p", "compiler_builtins"])
+        .args(&["-p", "std_unicode"])
+        .arg("--manifest-path")
+        .arg(builder.src.join("src/rustc/compiler_builtins_shim/Cargo.toml"));
+}
+
 /// Configure cargo to compile the standard library, adding appropriate env vars
 /// and such.
 pub fn std_cargo(builder: &Builder,
                  compiler: &Compiler,
                  target: Interned<String>,
                  cargo: &mut Command) {
-    if let Some(target) = env::var_os("MACOSX_STD_DEPLOYMENT_TARGET") {
-        cargo.env("MACOSX_DEPLOYMENT_TARGET", target);
-    }
+    mac_os_deployment_env_var(cargo);
 
-    if builder.no_std(target) == Some(true) {
-        // for no-std targets we only compile a few no_std crates
-        cargo.arg("--features").arg("c mem")
-            .args(&["-p", "alloc"])
-            .args(&["-p", "compiler_builtins"])
-            .args(&["-p", "std_unicode"])
-            .arg("--manifest-path")
-            .arg(builder.src.join("src/rustc/compiler_builtins_shim/Cargo.toml"));
-    } else {
-        let mut features = builder.std_features();
-
-        // When doing a local rebuild we tell cargo that we're stage1 rather than
-        // stage0. This works fine if the local rust and being-built rust have the
-        // same view of what the default allocator is, but fails otherwise. Since
-        // we don't have a way to express an allocator preference yet, work
-        // around the issue in the case of a local rebuild with jemalloc disabled.
-        if compiler.stage == 0 && builder.local_rebuild && !builder.config.use_jemalloc {
-            features.push_str(" force_alloc_system");
-        }
+    let mut features = builder.std_features();
 
-        if compiler.stage != 0 && builder.config.sanitizers {
-            // This variable is used by the sanitizer runtime crates, e.g.
-            // rustc_lsan, to build the sanitizer runtime from C code
-            // When this variable is missing, those crates won't compile the C code,
-            // so we don't set this variable during stage0 where llvm-config is
-            // missing
-            // We also only build the runtimes when --enable-sanitizers (or its
-            // config.toml equivalent) is used
-            let llvm_config = builder.ensure(native::Llvm {
-                target: builder.config.build,
-                emscripten: false,
-            });
-            cargo.env("LLVM_CONFIG", llvm_config);
-        }
+    // When doing a local rebuild we tell cargo that we're stage1 rather than
+    // stage0. This works fine if the local rust and being-built rust have the
+    // same view of what the default allocator is, but fails otherwise. Since
+    // we don't have a way to express an allocator preference yet, work
+    // around the issue in the case of a local rebuild with jemalloc disabled.
+    if compiler.stage == 0 && builder.local_rebuild && !builder.config.use_jemalloc {
+        features.push_str(" force_alloc_system");
+    }
 
-        cargo.arg("--features").arg(features)
-            .arg("--manifest-path")
-            .arg(builder.src.join("src/libstd/Cargo.toml"));
+    if compiler.stage != 0 && builder.config.sanitizers {
+        // This variable is used by the sanitizer runtime crates, e.g.
+        // rustc_lsan, to build the sanitizer runtime from C code
+        // When this variable is missing, those crates won't compile the C code,
+        // so we don't set this variable during stage0 where llvm-config is
+        // missing
+        // We also only build the runtimes when --enable-sanitizers (or its
+        // config.toml equivalent) is used
+        let llvm_config = builder.ensure(native::Llvm {
+            target: builder.config.build,
+            emscripten: false,
+        });
+        cargo.env("LLVM_CONFIG", llvm_config);
+    }
 
-        if let Some(target) = builder.config.target_config.get(&target) {
-            if let Some(ref jemalloc) = target.jemalloc {
-                cargo.env("JEMALLOC_OVERRIDE", jemalloc);
-            }
+    cargo.arg("--features").arg(features)
+        .arg("--manifest-path")
+        .arg(builder.src.join("src/libstd/Cargo.toml"));
+
+    if let Some(target) = builder.config.target_config.get(&target) {
+        if let Some(ref jemalloc) = target.jemalloc {
+            cargo.env("JEMALLOC_OVERRIDE", jemalloc);
         }
-        if target.contains("musl") {
-            if let Some(p) = builder.musl_root(target) {
-                cargo.env("MUSL_ROOT", p);
-            }
+    }
+    if target.contains("musl") {
+        if let Some(p) = builder.musl_root(target) {
+            cargo.env("MUSL_ROOT", p);
         }
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+struct CoreLink {
+    pub compiler: Compiler,
+    pub target_compiler: Compiler,
+    pub target: Interned<String>,
+}
+
+impl Step for CoreLink {
+    type Output = ();
+
+    fn should_run(run: ShouldRun) -> ShouldRun {
+        run.never()
+    }
+
+    /// Link all libcore rlibs/dylibs into the sysroot location.
+    ///
+    /// Links those artifacts generated by `compiler` to a the `stage` compiler's
+    /// sysroot for the specified `host` and `target`.
+    ///
+    /// Note that this assumes that `compiler` has already generated the
+    /// libraries for `target`, and this method will find them in the relevant
+    /// output directory.
+    fn run(self, builder: &Builder) {
+        let compiler = self.compiler;
+        let target_compiler = self.target_compiler;
+        let target = self.target;
+        builder.info(&format!("Copying stage{} core from stage{} ({} -> {} / {})",
+                target_compiler.stage,
+                compiler.stage,
+                &compiler.host,
+                target_compiler.host,
+                target));
+        let libdir = builder.sysroot_libdir(target_compiler, target);
+        add_to_sysroot(builder, &libdir, &libcore_stamp(builder, compiler, target));
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 struct StdLink {
     pub compiler: Compiler,
@@ -236,12 +313,6 @@ impl Step for StdLink {
             // for reason why the sanitizers are not built in stage0.
             copy_apple_sanitizer_dylibs(builder, &builder.native_dir(target), "osx", &libdir);
         }
-
-        builder.ensure(tool::CleanTools {
-            compiler: target_compiler,
-            target,
-            cause: Mode::Std,
-        });
     }
 }
 
@@ -369,6 +440,7 @@ impl Step for Test {
         }
 
         let out_dir = builder.cargo_out(compiler, Mode::Test, target);
+        builder.clear_if_dirty(&out_dir, &libcore_stamp(builder, compiler, target));
         builder.clear_if_dirty(&out_dir, &libstd_stamp(builder, compiler, target));
         let mut cargo = builder.cargo(compiler, Mode::Test, target, "build");
         test_cargo(builder, &compiler, target, &mut cargo);
@@ -394,9 +466,7 @@ pub fn test_cargo(builder: &Builder,
                   _compiler: &Compiler,
                   _target: Interned<String>,
                   cargo: &mut Command) {
-    if let Some(target) = env::var_os("MACOSX_STD_DEPLOYMENT_TARGET") {
-        cargo.env("MACOSX_DEPLOYMENT_TARGET", target);
-    }
+    mac_os_deployment_env_var(cargo);
     cargo.arg("--manifest-path")
         .arg(builder.src.join("src/libtest/Cargo.toml"));
 }
@@ -490,6 +560,7 @@ impl Step for Rustc {
             target: builder.config.build,
         });
         let cargo_out = builder.cargo_out(compiler, Mode::Rustc, target);
+        builder.clear_if_dirty(&cargo_out, &libcore_stamp(builder, compiler, target));
         builder.clear_if_dirty(&cargo_out, &libstd_stamp(builder, compiler, target));
         builder.clear_if_dirty(&cargo_out, &libtest_stamp(builder, compiler, target));
 
@@ -653,7 +724,7 @@ impl Step for CodegenBackend {
         if builder.config.dry_run {
             return;
         }
-        let mut files = files.into_iter()
+        let mut files = files.iter()
             .filter(|f| {
                 let filename = f.file_name().unwrap().to_str().unwrap();
                 is_dylib(filename) && filename.contains("rustc_codegen_llvm-")
@@ -790,6 +861,12 @@ fn copy_lld_to_sysroot(builder: &Builder,
     builder.copy(&lld_install_root.join("bin").join(&exe), &dst.join(&exe));
 }
 
+/// Cargo's output path for libcore in a given stage, compiled
+/// by a particular compiler for the specified target.
+pub fn libcore_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
+    builder.cargo_out(compiler, Mode::Std, target).join(".libcore.stamp")
+}
+
 /// Cargo's output path for the standard library in a given stage, compiled
 /// by a particular compiler for the specified target.
 pub fn libstd_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
@@ -921,6 +998,7 @@ impl Step for Assemble {
             for stage in 0..min(target_compiler.stage, builder.config.keep_stage.unwrap()) {
                 let target_compiler = builder.compiler(stage, target_compiler.host);
                 let target = target_compiler.host;
+                builder.ensure(CoreLink { compiler, target_compiler, target });
                 builder.ensure(StdLink { compiler, target_compiler, target });
                 builder.ensure(TestLink { compiler, target_compiler, target });
                 builder.ensure(RustcLink { compiler, target_compiler, target });
@@ -1043,28 +1121,28 @@ pub fn run_cargo(builder: &Builder, cargo: &mut Command, stamp: &Path, is_check:
             CargoMessage::CompilerArtifact { filenames, .. } => filenames,
             _ => return,
         };
-        for filename in filenames {
+        for filename in filenames.iter() {
             // Skip files like executables
             if !filename.ends_with(".rlib") &&
                !filename.ends_with(".lib") &&
                !is_dylib(&filename) &&
                !(is_check && filename.ends_with(".rmeta")) {
-                return;
+                break;
             }
 
-            let filename = Path::new(&*filename);
+            let filename = Path::new(&**filename);
 
             // If this was an output file in the "host dir" we don't actually
             // worry about it, it's not relevant for us.
             if filename.starts_with(&host_root_dir) {
-                return;
+                break;
             }
 
             // If this was output in the `deps` dir then this is a precise file
             // name (hash included) so we start tracking it.
             if filename.starts_with(&target_deps_dir) {
                 deps.push(filename.to_path_buf());
-                return;
+                break;
             }
 
             // Otherwise this was a "top level artifact" which right now doesn't
@@ -1085,6 +1163,33 @@ pub fn run_cargo(builder: &Builder, cargo: &mut Command, stamp: &Path, is_check:
 
             toplevel.push((file_stem, extension, expected_len));
         }
+        for filename in filenames {
+            // Skip files like executables
+            if !filename.ends_with(".rlib") &&
+               !filename.ends_with(".lib") &&
+               !is_dylib(&filename) &&
+               !(is_check && filename.ends_with(".rmeta")) {
+                break;
+            }
+
+            let filename = Path::new(&*filename);
+
+            // If this was an output file in the "host dir" we don't actually
+            // worry about it, it's not relevant for us.
+            if filename.starts_with(&host_root_dir) {
+                let f = filename.file_name();
+                if deps.iter().find(|v| v.file_name() == f).is_none() {
+                    deps.push(filename.to_path_buf());
+                }
+                continue;
+            }
+
+            // If this was output in the `deps` dir then this is a precise file
+            // name (hash included) so we start tracking it.
+            if filename.starts_with(&target_deps_dir) {
+                break;
+            }
+        }
     });
 
     if !ok {
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 6e77413f06188..8be42032f55e9 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -332,6 +332,18 @@ impl Mode {
             _ => false
         }
     }
+
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Mode::Std => "std",
+            Mode::Test => "test",
+            Mode::Rustc => "rustc",
+            Mode::Codegen => "codegen",
+            Mode::ToolStd => "tool",
+            Mode::ToolTest => "tool",
+            Mode::ToolRustc => "tool",
+        }
+    }
 }
 
 impl Build {
@@ -534,8 +546,8 @@ impl Build {
         let suffix = match mode {
             Mode::Std => "-std",
             Mode::Test => "-test",
-            Mode::Codegen => "-rustc",
             Mode::Rustc => "-rustc",
+            Mode::Codegen => "-codegen",
             Mode::ToolStd | Mode::ToolTest | Mode::ToolRustc => "-tools",
         };
         self.out.join(&*compiler.host)
diff --git a/src/liballoc_jemalloc/Cargo.toml b/src/liballoc_jemalloc/Cargo.toml
index 7986d5dd2eb54..8f52cbb2ea400 100644
--- a/src/liballoc_jemalloc/Cargo.toml
+++ b/src/liballoc_jemalloc/Cargo.toml
@@ -12,9 +12,7 @@ test = false
 doc = false
 
 [dependencies]
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
 
 [build-dependencies]
 build_helper = { path = "../build_helper" }
diff --git a/src/liballoc_system/Cargo.toml b/src/liballoc_system/Cargo.toml
index c34e2f203a837..cd4979e686544 100644
--- a/src/liballoc_system/Cargo.toml
+++ b/src/liballoc_system/Cargo.toml
@@ -10,9 +10,7 @@ test = false
 doc = false
 
 [dependencies]
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
 
 # See comments in the source for what this dependency is
 [target.'cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))'.dependencies]
diff --git a/src/libpanic_abort/Cargo.toml b/src/libpanic_abort/Cargo.toml
index 633d273b3b93c..7596e74a810d8 100644
--- a/src/libpanic_abort/Cargo.toml
+++ b/src/libpanic_abort/Cargo.toml
@@ -10,6 +10,4 @@ bench = false
 doc = false
 
 [dependencies]
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/libpanic_unwind/Cargo.toml b/src/libpanic_unwind/Cargo.toml
index 74aaa4d5ae3db..88469a43e8b7c 100644
--- a/src/libpanic_unwind/Cargo.toml
+++ b/src/libpanic_unwind/Cargo.toml
@@ -10,8 +10,5 @@ bench = false
 doc = false
 
 [dependencies]
-alloc = { path = "../liballoc" }
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
 unwind = { path = "../libunwind" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/libprofiler_builtins/Cargo.toml b/src/libprofiler_builtins/Cargo.toml
index 79192fbb6819c..c56962b4940ea 100644
--- a/src/libprofiler_builtins/Cargo.toml
+++ b/src/libprofiler_builtins/Cargo.toml
@@ -11,9 +11,5 @@ test = false
 bench = false
 doc = false
 
-[dependencies]
-core = { path = "../libcore" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
-
 [build-dependencies]
 cc = "1.0.1"
diff --git a/src/librustc_asan/Cargo.toml b/src/librustc_asan/Cargo.toml
index 34d8b75a5bfb3..fb735ea56efdb 100644
--- a/src/librustc_asan/Cargo.toml
+++ b/src/librustc_asan/Cargo.toml
@@ -14,7 +14,4 @@ build_helper = { path = "../build_helper" }
 cmake = "0.1.18"
 
 [dependencies]
-alloc = { path = "../liballoc" }
 alloc_system = { path = "../liballoc_system" }
-core = { path = "../libcore" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/librustc_codegen_llvm/Cargo.toml b/src/librustc_codegen_llvm/Cargo.toml
index 7cf0a1c1becaa..38b2f75502aee 100644
--- a/src/librustc_codegen_llvm/Cargo.toml
+++ b/src/librustc_codegen_llvm/Cargo.toml
@@ -10,39 +10,15 @@ crate-type = ["dylib"]
 test = false
 
 [dependencies]
-bitflags = "1.0.1"
 cc = "1.0.1"
-flate2 = "1.0"
-jobserver = "0.1.5"
-libc = "0.2"
-log = "0.4"
-num_cpus = "1.0"
-rustc = { path = "../librustc" }
 rustc-demangle = "0.1.4"
-rustc_allocator = { path = "../librustc_allocator" }
-rustc_apfloat = { path = "../librustc_apfloat" }
-rustc_target = { path = "../librustc_target" }
-rustc_data_structures = { path = "../librustc_data_structures" }
-rustc_errors = { path = "../librustc_errors" }
-rustc_incremental = { path = "../librustc_incremental" }
 rustc_llvm = { path = "../librustc_llvm" }
-rustc_platform_intrinsics = { path = "../librustc_platform_intrinsics" }
-rustc_codegen_utils = { path = "../librustc_codegen_utils" }
-rustc_mir = { path = "../librustc_mir" }
-serialize = { path = "../libserialize" }
-syntax = { path = "../libsyntax" }
-syntax_pos = { path = "../libsyntax_pos" }
-tempdir = "0.3"
 
 # not actually used but needed to make sure we enable the same feature set as
 # winapi used in librustc
 env_logger = { version = "0.5", default-features = false }
 
 [features]
-# Used to communicate the feature to `rustc_target` in the same manner that the
-# `rustc` driver script communicate this.
-jemalloc = ["rustc_target/jemalloc"]
-
 # This is used to convince Cargo to separately cache builds of `rustc_codegen_llvm`
 # when this option is enabled or not. That way we can build two, cache two
 # artifacts, and have nice speedy rebuilds.
diff --git a/src/librustc_llvm/Cargo.toml b/src/librustc_llvm/Cargo.toml
index 0978c2ceb141d..9c3003684c64d 100644
--- a/src/librustc_llvm/Cargo.toml
+++ b/src/librustc_llvm/Cargo.toml
@@ -13,9 +13,6 @@ static-libstdcpp = []
 emscripten = []
 
 [dependencies]
-bitflags = "1.0"
-libc = "0.2"
-rustc_cratesio_shim = { path = "../librustc_cratesio_shim" }
 
 [build-dependencies]
 build_helper = { path = "../build_helper" }
diff --git a/src/librustc_lsan/Cargo.toml b/src/librustc_lsan/Cargo.toml
index 9c19b53742654..e81c64111b10f 100644
--- a/src/librustc_lsan/Cargo.toml
+++ b/src/librustc_lsan/Cargo.toml
@@ -14,7 +14,4 @@ build_helper = { path = "../build_helper" }
 cmake = "0.1.18"
 
 [dependencies]
-alloc = { path = "../liballoc" }
 alloc_system = { path = "../liballoc_system" }
-core = { path = "../libcore" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/librustc_msan/Cargo.toml b/src/librustc_msan/Cargo.toml
index 17ec2b96438ad..b95fd93f1bec8 100644
--- a/src/librustc_msan/Cargo.toml
+++ b/src/librustc_msan/Cargo.toml
@@ -14,7 +14,4 @@ build_helper = { path = "../build_helper" }
 cmake = "0.1.18"
 
 [dependencies]
-alloc = { path = "../liballoc" }
 alloc_system = { path = "../liballoc_system" }
-core = { path = "../libcore" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/librustc_tsan/Cargo.toml b/src/librustc_tsan/Cargo.toml
index 8bb67c0bbac5f..29bf6033bf7a2 100644
--- a/src/librustc_tsan/Cargo.toml
+++ b/src/librustc_tsan/Cargo.toml
@@ -14,7 +14,4 @@ build_helper = { path = "../build_helper" }
 cmake = "0.1.18"
 
 [dependencies]
-alloc = { path = "../liballoc" }
 alloc_system = { path = "../liballoc_system" }
-core = { path = "../libcore" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/libstd/Cargo.toml b/src/libstd/Cargo.toml
index 5a2dce5930a4b..670e61bba549f 100644
--- a/src/libstd/Cargo.toml
+++ b/src/libstd/Cargo.toml
@@ -13,17 +13,29 @@ path = "lib.rs"
 crate-type = ["dylib", "rlib"]
 
 [dependencies]
-alloc = { path = "../liballoc" }
 alloc_jemalloc = { path = "../liballoc_jemalloc", optional = true }
 alloc_system = { path = "../liballoc_system" }
 panic_unwind = { path = "../libpanic_unwind", optional = true }
 panic_abort = { path = "../libpanic_abort" }
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
 profiler_builtins = { path = "../libprofiler_builtins", optional = true }
-std_unicode = { path = "../libstd_unicode" }
 unwind = { path = "../libunwind" }
+object = { version = "0.9", default-features = false, optional = true }
+
+[dependencies.gimli]
+version = "0.16"
+default-features = false
+features = ["alloc"]
+git = "https://github.com/est31/gimli"
+rev = "304caacf8b73f117813b1a0d436ce24403459bf2"
+optional = true
+
+[dependencies.addr2line]
+git = "https://github.com/est31/addr2line"
+branch = "no_std_prototype"
+default-features = false
+features = ["cpp_demangle"]
+optional = true
 
 [dev-dependencies]
 rand = "0.4"
@@ -43,7 +55,7 @@ cc = "1.0"
 build_helper = { path = "../build_helper" }
 
 [features]
-backtrace = []
+backtrace = ["addr2line", "object", "gimli"]
 debug-jemalloc = ["alloc_jemalloc/debug"]
 jemalloc = ["alloc_jemalloc"]
 force_alloc_system = []
diff --git a/src/libstd/build.rs b/src/libstd/build.rs
index c001e4e8cebf9..679ae6cb4c7c9 100644
--- a/src/libstd/build.rs
+++ b/src/libstd/build.rs
@@ -13,21 +13,10 @@
 extern crate build_helper;
 extern crate cc;
 
-use build_helper::native_lib_boilerplate;
 use std::env;
-use std::fs::File;
 
 fn main() {
     let target = env::var("TARGET").expect("TARGET was not set");
-    if cfg!(feature = "backtrace") &&
-        !target.contains("cloudabi") &&
-        !target.contains("emscripten") &&
-        !target.contains("fuchsia") &&
-        !target.contains("msvc") &&
-        !target.contains("wasm32")
-    {
-        let _ = build_libbacktrace(&target);
-    }
 
     if target.contains("linux") {
         if target.contains("android") {
@@ -82,56 +71,3 @@ fn main() {
         println!("cargo:rustc-link-lib=compiler_rt");
     }
 }
-
-fn build_libbacktrace(target: &str) -> Result<(), ()> {
-    let native = native_lib_boilerplate("libbacktrace", "libbacktrace", "backtrace", "")?;
-
-    let mut build = cc::Build::new();
-    build
-        .flag("-fvisibility=hidden")
-        .include("../libbacktrace")
-        .include(&native.out_dir)
-        .out_dir(&native.out_dir)
-        .warnings(false)
-        .file("../libbacktrace/alloc.c")
-        .file("../libbacktrace/backtrace.c")
-        .file("../libbacktrace/dwarf.c")
-        .file("../libbacktrace/fileline.c")
-        .file("../libbacktrace/posix.c")
-        .file("../libbacktrace/read.c")
-        .file("../libbacktrace/sort.c")
-        .file("../libbacktrace/state.c");
-
-    if target.contains("darwin") {
-        build.file("../libbacktrace/macho.c");
-    } else if target.contains("windows") {
-        build.file("../libbacktrace/pecoff.c");
-    } else {
-        build.file("../libbacktrace/elf.c");
-
-        if target.contains("64") {
-            build.define("BACKTRACE_ELF_SIZE", "64");
-        } else {
-            build.define("BACKTRACE_ELF_SIZE", "32");
-        }
-    }
-
-    File::create(native.out_dir.join("backtrace-supported.h")).unwrap();
-    build.define("BACKTRACE_SUPPORTED", "1");
-    build.define("BACKTRACE_USES_MALLOC", "1");
-    build.define("BACKTRACE_SUPPORTS_THREADS", "0");
-    build.define("BACKTRACE_SUPPORTS_DATA", "0");
-
-    File::create(native.out_dir.join("config.h")).unwrap();
-    if !target.contains("apple-ios") &&
-       !target.contains("solaris") &&
-       !target.contains("redox") &&
-       !target.contains("android") {
-        build.define("HAVE_DL_ITERATE_PHDR", "1");
-    }
-    build.define("_GNU_SOURCE", "1");
-    build.define("_LARGE_FILES", "1");
-
-    build.compile("backtrace");
-    Ok(())
-}
diff --git a/src/libstd/sys/unix/backtrace/printing/mod.rs b/src/libstd/sys/unix/backtrace/printing/mod.rs
index caa60712b1d58..5a879dbe8f68e 100644
--- a/src/libstd/sys/unix/backtrace/printing/mod.rs
+++ b/src/libstd/sys/unix/backtrace/printing/mod.rs
@@ -25,10 +25,10 @@ where
     Ok(false)
 }
 
-#[cfg(not(target_os = "emscripten"))]
+#[cfg(target_os = "fuchsia")]
 pub use sys_common::gnu::libbacktrace::foreach_symbol_fileline;
 
-#[cfg(not(target_os = "emscripten"))]
+#[cfg(target_os = "fuchsia")]
 pub fn resolve_symname<F>(frame: Frame, callback: F, bc: &BacktraceContext) -> io::Result<()>
 where
     F: FnOnce(Option<&str>) -> io::Result<()>
@@ -41,3 +41,20 @@ where
         }
     }, bc)
 }
+
+#[cfg(not(any(target_os = "fuchsia", target_os = "emscripten")))]
+pub use sys_common::addr2line::foreach_symbol_fileline;
+
+#[cfg(not(any(target_os = "fuchsia", target_os = "emscripten")))]
+pub fn resolve_symname<F>(frame: Frame, callback: F, bc: &BacktraceContext) -> io::Result<()>
+where
+    F: FnOnce(Option<&str>) -> io::Result<()>
+{
+    ::sys_common::addr2line::resolve_symname(frame, |symname| {
+        if symname.is_some() {
+            callback(symname)
+        } else {
+            dladdr::resolve_symname(frame, callback, bc)
+        }
+    }, bc)
+}
diff --git a/src/libstd/sys_common/addr2line.rs b/src/libstd/sys_common/addr2line.rs
new file mode 100644
index 0000000000000..2fa7e822f1738
--- /dev/null
+++ b/src/libstd/sys_common/addr2line.rs
@@ -0,0 +1,143 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern crate addr2line;
+extern crate gimli;
+extern crate object;
+
+use libc::{mmap, size_t, PROT_READ, MAP_SHARED, MAP_FAILED};
+
+use io;
+use ptr;
+use env;
+
+use cell::UnsafeCell;
+use marker::Sync;
+use sys::backtrace::BacktraceContext;
+use sys_common::backtrace::Frame;
+use os::unix::io::AsRawFd;
+use fs::File;
+use slice::from_raw_parts;
+use self::addr2line::Context;
+use self::gimli::{EndianRcSlice, RunTimeEndian};
+
+struct ThreadSafe<T>(UnsafeCell<T>);
+
+unsafe impl<T> Sync for ThreadSafe<T> {}
+
+macro_rules! err {
+    ($e:expr) => {
+        return Err(io::Error::new(
+            io::ErrorKind::Other,
+            $e)
+        );
+    }
+}
+
+struct Ctx {
+    ctx: Context<EndianRcSlice<RunTimeEndian>>,
+    _file: File,
+}
+
+impl Ctx {
+    fn init() -> io::Result<Ctx> {
+        let filename = env::current_exe()?;
+        let file = File::open(&filename)?;
+        let file_len = file.metadata()?.len();
+
+        let map_ptr = unsafe {
+            mmap(ptr::null_mut(),
+                file_len as size_t,
+                PROT_READ,
+                MAP_SHARED,
+                file.as_raw_fd(),
+                0)
+        };
+        if map_ptr == MAP_FAILED {
+            err!("mapping the executable into memory failed");
+        }
+
+        let map = unsafe { from_raw_parts(map_ptr as * mut u8, file_len as usize) };
+        let object_file = match object::File::parse(&*map) {
+            Ok(v) => v,
+            Err(_) => err!("could not parse the object file for backtrace creation"),
+        };
+        let ctx = match Context::new(&object_file) {
+            Ok(v) => v,
+            Err(_) => err!("could not create backtrace parsing context"),
+        };
+
+        Ok(Ctx {
+            ctx,
+            _file: file,
+        })
+    }
+    fn with_static<T, F: FnOnce(&Ctx) -> io::Result<T>>(f: F) -> io::Result<T> {
+        static CTX_CELL: ThreadSafe<Option<Ctx>> = ThreadSafe(UnsafeCell::new(None));
+        let cell_ref: &mut Option<_> = unsafe { &mut *CTX_CELL.0.get() };
+        if cell_ref.is_none() {
+            *cell_ref = Some(Ctx::init()?);
+        }
+        let ctx = if let Some(c) = cell_ref {
+            c
+        } else {
+            unreachable!()
+        };
+        f(ctx)
+    }
+}
+
+pub fn foreach_symbol_fileline<F>(frame: Frame,
+                                  mut f: F,
+                                  _: &BacktraceContext) -> io::Result<bool>
+where F: FnMut(&[u8], u32) -> io::Result<()>
+{
+    Ctx::with_static(|ctx|{
+        let mut frames_iter = match ctx.ctx.find_frames(frame.exact_position as u64) {
+            Ok(v) => v,
+            Err(_) => err!("error during binary parsing"),
+        };
+        for frame_opt in frames_iter.next() {
+            let loc_opt = frame_opt.and_then(|v| v.location);
+            let file_line_opt = loc_opt.map(|v| (v.file, v.line));
+            if let Some((Some(file), Some(line))) = file_line_opt {
+                f(file.as_bytes(), line as u32)?;
+            }
+        }
+        // FIXME: when should we return true here?
+        Ok(false)
+    })
+}
+
+/// Converts a pointer to symbol to its string value.
+pub fn resolve_symname<F>(frame: Frame,
+                          callback: F,
+                          _: &BacktraceContext) -> io::Result<()>
+    where F: FnOnce(Option<&str>) -> io::Result<()>
+{
+    Ctx::with_static(|ctx|{
+        let mut frames_iter = match ctx.ctx.find_frames(frame.symbol_addr as u64) {
+            Ok(v) => v,
+            Err(_) => err!("error during binary parsing"),
+        };
+        let frame_opt = match frames_iter.next() {
+            Ok(v) => v,
+            Err(_) => err!("error during symbolification"),
+        };
+        match frame_opt.and_then(|v| v.function) {
+            Some(n) => match n.raw_name() {
+                Ok(v) => callback(Some(&*v))?,
+                Err(_) => err!("error during name resolval"),
+            },
+            None => callback(None)?,
+        }
+        Ok(())
+    })
+}
diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
index d0c4d6a773746..6fdc8bdfa7461 100644
--- a/src/libstd/sys_common/mod.rs
+++ b/src/libstd/sys_common/mod.rs
@@ -66,11 +66,13 @@ cfg_if! {
 }
 
 #[cfg(feature = "backtrace")]
-#[cfg(any(all(unix, not(target_os = "emscripten")),
-          all(windows, target_env = "gnu"),
-          target_os = "redox"))]
+#[cfg(target_os = "fuchsia")]
 pub mod gnu;
 
+#[cfg(feature = "backtrace")]
+#[cfg(not(target_os = "fuchsia"))]
+pub mod addr2line;
+
 // common error constructors
 
 /// A trait for viewing representations from std types
diff --git a/src/libunwind/Cargo.toml b/src/libunwind/Cargo.toml
index 4760461df64e3..44a99b3a0cc48 100644
--- a/src/libunwind/Cargo.toml
+++ b/src/libunwind/Cargo.toml
@@ -12,6 +12,4 @@ bench = false
 doc = false
 
 [dependencies]
-core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
-compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
diff --git a/src/rustc/dlmalloc_shim/Cargo.toml b/src/rustc/dlmalloc_shim/Cargo.toml
index b6f8550829fe0..7edbda009e894 100644
--- a/src/rustc/dlmalloc_shim/Cargo.toml
+++ b/src/rustc/dlmalloc_shim/Cargo.toml
@@ -8,7 +8,3 @@ path = "../../dlmalloc/src/lib.rs"
 test = false
 bench = false
 doc = false
-
-[dependencies]
-core = { path = "../../libcore" }
-compiler_builtins = { path = "../../rustc/compiler_builtins_shim" }
diff --git a/src/rustc/libc_shim/Cargo.toml b/src/rustc/libc_shim/Cargo.toml
index e77897d643313..09b2bed919a5c 100644
--- a/src/rustc/libc_shim/Cargo.toml
+++ b/src/rustc/libc_shim/Cargo.toml
@@ -10,28 +10,6 @@ test = false
 bench = false
 doc = false
 
-[dependencies]
-# Specify the path to libcore; at the time of writing, removing this shim in
-# favor of using libc from git results in a compilation failure:
-#
-# Building stage0 std artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
-#    Compiling libc v0.0.0 (file:///Users/tamird/src/rust/src/rustc/libc_shim)
-# error[E0463]: can't find crate for `core`
-#
-# error: aborting due to previous error
-#
-# error: Could not compile `libc`.
-#
-# Caused by:
-#   process didn't exit successfully: `/Users/tamird/src/rust/build/bootstrap/debug/rustc --crate-name libc src/rustc/libc_shim/../../liblibc/src/lib.rs --error-format json --crate-type lib --emit=dep-info,link -C opt-level=2 --cfg feature="default" --cfg feature="no_std" --cfg feature="stdbuild" -C metadata=d758f87058112d7d -C extra-filename=-d758f87058112d7d --out-dir /Users/tamird/src/rust/build/x86_64-apple-darwin/stage0-std/x86_64-apple-darwin/release/deps --target x86_64-apple-darwin -L dependency=/Users/tamird/src/rust/build/x86_64-apple-darwin/stage0-std/x86_64-apple-darwin/release/deps -L dependency=/Users/tamird/src/rust/build/x86_64-apple-darwin/stage0-std/release/deps` (exit code: 101)
-# thread 'main' panicked at 'command did not execute successfully: "/Users/tamird/src/rust/build/x86_64-apple-darwin/stage0/bin/cargo" "build" "-j" "4" "--target" "x86_64-apple-darwin" "--release" "--features" "panic-unwind jemalloc backtrace" "--manifest-path" "/Users/tamird/src/rust/src/libstd/Cargo.toml" "--message-format" "json"
-# expected success, got: exit code: 101', src/bootstrap/compile.rs:883:8
-#
-# See https://github.com/rust-lang/rfcs/pull/1133.
-core = { path = "../../libcore" }
-compiler_builtins = { path = "../compiler_builtins_shim" }
-
-
 [features]
 # Certain parts of libc are conditionally compiled differently than when used
 # outside rustc. See https://github.com/rust-lang/libc/search?l=Rust&q=stdbuild&type=&utf8=%E2%9C%93.