amdgcn target failling to build compiler_builtins (and thus all examples)

[ZuseZ4]

I tried this code:

// src/lib.rs
#![feature(abi_gpu_kernel)]
#![no_std]

#[panic_handler]
fn panic(_: &core::panic::PanicInfo) -> ! {
    loop {}
}

#[no_mangle]
pub extern "gpu-kernel" fn kernel(/* Arguments */) {
    // Code
}

I expected to see this happen: compiles with RUSTFLAGS="-Ctarget-cpu=gfx90a" cargo +offload build -Zunstable-options -r -v --target amdgcn-amd-amdhsa -Zbuild-std=core

Instead, this happened: ICE.

rustc: /mypath/rust/src/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp:962: virtual bool llvm::AMDGPUTargetLowering::isFNegFree(EVT) const: Assertion `VT.isFloatingPoint()' failed.

If I adjust the rustc command and only emit llvm-ir, we can trigger a probably related, slightly different bug:

void expandIToFP(Instruction *): Assertion `BitWidth > FloatWidth && "Unexpected conversion. expandIToFP() " "assumes integer width is larger than fp."' failed.

I attached the llvm-ir

Meta

self-build rustc based on the latest master (with optionaly cherry-picking #136840). An official nightly just get's a SEGSEGV, probably due to not having llvm assertions on. I get the same behvaiour with a local build if I disable the llvm assertion on line 962 (see above).
rustc --version --verbose:

cargo 1.90.0-nightly (6833aa715 2025-07-13)

Backtrace

mypathto/.rustup/toolchains/offload/bin/rustc --crate-name compiler_builtins --edition=2024 someotherpath/prog/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/src/rust/library/compiler-builtins/compiler-builtins/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=364 --crate-type lib --emit=dep-info,metadata,link,llvm-ir -C opt-level=3 -C panic=abort -C linker-plugin-lto --cfg 'feature="compiler-builtins"' --cfg 'feature="default"' --cfg 'feature="rustc-dep-of-std"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("c", "compiler-builtins", "default", "mangled-names", "mem", "no-asm", "no-f16-f128", "rustc-dep-of-std", "unstable-public-internals"))' -C metadata=eff520098f2ad113 -C extra-filename=-0b43525578c04b1d --out-dir athirdpath/prog/offload/r/target/amdgcn-amd-amdhsa/release/deps --target amdgcn-amd-amdhsa -C strip=debuginfo -Z force-unstable-if-unmarked -L dependency=athirdpath/prog/offload/r/target/amdgcn-amd-amdhsa/release/deps -L dependency=athirdpath/prog/offload/r/target/release/deps --extern core=athirdpath/prog/offload/r/target/amdgcn-amd-amdhsa/release/deps/libcore-ff3c37dfbfae9622.rmeta --cap-lints allow -Ctarget-cpu=gfx90a --cfg f16_enabled --cfg f128_enabled --cfg intrinsics_enabled --cfg arch_enabled --cfg optimizations_enabled --cfg 'feature="unstable-intrinsics"' --check-cfg 'cfg(__ashldi3, values("optimized-c"))' --check-cfg 'cfg(__ashlsi3, values("optimized-c"))' --check-cfg 'cfg(__ashrdi3, values("optimized-c"))' --check-cfg 'cfg(__ashrsi3, values("optimized-c"))' --check-cfg 'cfg(__bswapsi2, values("optimized-c"))' --check-cfg 'cfg(__bswapdi2, values("optimized-c"))' --check-cfg 'cfg(__bswapti2, values("optimized-c"))' --check-cfg 'cfg(__divdi3, values("optimized-c"))' --check-cfg 'cfg(__divsi3, values("optimized-c"))' --check-cfg 'cfg(__divmoddi4, values("optimized-c"))' --check-cfg 'cfg(__divmodsi4, values("optimized-c"))' --check-cfg 'cfg(__divmodsi4, values("optimized-c"))' --check-cfg 'cfg(__divmodti4, values("optimized-c"))' --check-cfg 'cfg(__lshrdi3, values("optimized-c"))' --check-cfg 'cfg(__lshrsi3, values("optimized-c"))' --check-cfg 'cfg(__moddi3, values("optimized-c"))' --check-cfg 'cfg(__modsi3, values("optimized-c"))' --check-cfg 'cfg(__muldi3, values("optimized-c"))' --check-cfg 'cfg(__udivdi3, values("optimized-c"))' --check-cfg 'cfg(__udivmoddi4, values("optimized-c"))' --check-cfg 'cfg(__udivmodsi4, values("optimized-c"))' --check-cfg 'cfg(__udivsi3, values("optimized-c"))' --check-cfg 'cfg(__umoddi3, values("optimized-c"))' --check-cfg 'cfg(__umodsi3, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas16_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas16_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas16_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_cas16_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldadd8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldclr8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldeor8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_ldset8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp1_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp1_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp1_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp1_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp2_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp2_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp2_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp2_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp4_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp4_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp4_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp4_acq_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp8_relax, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp8_acq, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp8_rel, values("optimized-c"))' --check-cfg 'cfg(__aarch64_swp8_acq_rel, values("optimized-c"))' --check-cfg 'cfg(target_feature, values("vis3"))' --check-cfg 'cfg(feature, values("checked"))' --check-cfg 'cfg(assert_no_panic)' --check-cfg 'cfg(thumb)' --check-cfg 'cfg(thumb_1)' --check-cfg 'cfg(f16_enabled)' --check-cfg 'cfg(f128_enabled)' --check-cfg 'cfg(intrinsics_enabled)' --check-cfg 'cfg(arch_enabled)' --check-cfg 'cfg(optimizations_enabled)' --check-cfg 'cfg(feature, values("unstable-public-internals"))' --check-cfg 'cfg(optimizations_enabled)' --check-cfg 'cfg(x86_no_sse)' --check-cfg 'cfg(kernel_user_helpers)' --check-cfg 'cfg(feature, values("mem-unaligned"))'
{"$message_type":"artifact","artifact":"athirdpath/prog/offload/r/target/amdgcn-amd-amdhsa/release/deps/compiler_builtins-0b43525578c04b1d.d","emit":"dep-info"}
{"$message_type":"artifact","artifact":"athirdpath/prog/offload/r/target/amdgcn-amd-amdhsa/release/deps/libcompiler_builtins-0b43525578c04b1d.rmeta","emit":"metadata"}
rustc: someotherpath/prog/rust/src/llvm-project/llvm/lib/CodeGen/ExpandLargeFpConvert.cpp:327: void expandIToFP(Instruction *): Assertion `BitWidth > FloatWidth && "Unexpected conversion. expandIToFP() " "assumes integer width is larger than fp."' failed.
zsh: abort (core dumped)  mypathto/.rustup/toolchains/offload/bin/rustc --crate-name        lib

[ZuseZ4]

I looked a bit into it with @shiltian, who pointed out I had f128 casts in it, which shouldn't be there.
@Flakebi so it seems that this regressed, causing issues on my gfx90a.
I couldn't find the logic in the compiler-builtins anymore, but instead

let reliable_f128 = rustc_output_ok && rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"); 

hard-coding that line to false lets me compile a kernel.

[ZuseZ4]

rustc +offload --print=cfg --target amdgcn-amd-amdhsa
debug_assertions
fmt_debug="full"
overflow_checks
panic="abort"
relocation_model="pic"
target_abi=""
target_arch="amdgpu"
target_endian="little"
target_env=""
target_has_atomic
target_has_atomic="16"
target_has_atomic="32"
target_has_atomic="64"
target_has_atomic="8"
target_has_atomic="ptr"
target_has_atomic_equal_alignment="16"
target_has_atomic_equal_alignment="32"
target_has_atomic_equal_alignment="64"
target_has_atomic_equal_alignment="8"
target_has_atomic_equal_alignment="ptr"
target_has_atomic_load_store
target_has_atomic_load_store="16"
target_has_atomic_load_store="32"
target_has_atomic_load_store="64"
target_has_atomic_load_store="8"
target_has_atomic_load_store="ptr"
target_has_reliable_f128
target_has_reliable_f16
target_has_reliable_f16_math
target_os="amdhsa"
target_pointer_width="64"
target_vendor="amd"
ub_checks

I guess target_has_reliable_f128 shouldn't be there?

[compiler/rustc_codegen_llvm/src/llvm_util.rs:440:5] &target_arch = "amdgpu"
[compiler/rustc_codegen_llvm/src/llvm_util.rs:441:5] &target_os = "amdhsa"
[compiler/rustc_codegen_llvm/src/llvm_util.rs:442:5] &cfg.has_reliable_f128 = true