[WebAssembly] Add support for memcmp expansion #148298

badumbatish · 2025-07-11T21:17:02Z

Fixes #61400

Added test case in llvm/test/CodeGen/WebAssembly/memcmp-expand.ll

llvmbot · 2025-07-11T21:17:40Z

@llvm/pr-subscribers-backend-webassembly

Author: jjasmine (badumbatish)

Changes

Fixes #61400

Added test case in llvm/test/CodeGen/WebAssembly/memcmp-expand.ll

Full diff: https://github.com/llvm/llvm-project/pull/148298.diff

4 Files Affected:

(modified) llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp (+4)
(modified) llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp (+10)
(modified) llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.h (+4)
(added) llvm/test/CodeGen/WebAssembly/memcmp-expand.ll (+146)

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index bf2e04caa0a61..a91a58db2a422 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -46,6 +46,10 @@ WebAssemblyTargetLowering::WebAssemblyTargetLowering(
     : TargetLowering(TM), Subtarget(&STI) {
   auto MVTPtr = Subtarget->hasAddr64() ? MVT::i64 : MVT::i32;
 
+  // Set the load count for memcmp expand optimization
+  MaxLoadsPerMemcmp = 3;
+  MaxLoadsPerMemcmpOptSize = 2;
+
   // Booleans always contain 0 or 1.
   setBooleanContents(ZeroOrOneBooleanContent);
   // Except in SIMD vectors
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp
index 4f159996e4c6c..3686fce33f3ca 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp
@@ -141,6 +141,16 @@ InstructionCost WebAssemblyTTIImpl::getCastInstrCost(
   return BaseT::getCastInstrCost(Opcode, Dst, Src, CCH, CostKind, I);
 }
 
+WebAssemblyTTIImpl::TTI::MemCmpExpansionOptions
+WebAssemblyTTIImpl::enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const {
+  TTI::MemCmpExpansionOptions Options;
+  // INFO: I'm not sure what determines this, setting 2 conservatively
+  Options.NumLoadsPerBlock = 2;
+  Options.LoadSizes.append({8, 4, 2, 1});
+  Options.MaxNumLoads = TLI->getMaxExpandSizeMemcmp(OptSize);
+  return Options;
+}
+
 InstructionCost WebAssemblyTTIImpl::getMemoryOpCost(
     unsigned Opcode, Type *Ty, Align Alignment, unsigned AddressSpace,
     TTI::TargetCostKind CostKind, TTI::OperandValueInfo OpInfo,
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.h b/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.h
index d83b8d1f45dbd..c915eeb07d4fd 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.h
@@ -73,6 +73,10 @@ class WebAssemblyTTIImpl final : public BasicTTIImplBase<WebAssemblyTTIImpl> {
   getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src,
                    TTI::CastContextHint CCH, TTI::TargetCostKind CostKind,
                    const Instruction *I = nullptr) const override;
+
+  TTI::MemCmpExpansionOptions
+  enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const override;
+
   InstructionCost getMemoryOpCost(
       unsigned Opcode, Type *Src, Align Alignment, unsigned AddressSpace,
       TTI::TargetCostKind CostKind,
diff --git a/llvm/test/CodeGen/WebAssembly/memcmp-expand.ll b/llvm/test/CodeGen/WebAssembly/memcmp-expand.ll
new file mode 100644
index 0000000000000..64476e3b0b844
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/memcmp-expand.ll
@@ -0,0 +1,146 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s  -O3 -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s
+
+target triple = "wasm32-unknown-unknown"
+
+declare i32 @memcmp(ptr, ptr, i32)
+
+define i1 @memcmp_expand_3(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_3:
+; CHECK:         .functype memcmp_expand_3 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    i32.load16_u $push7=, 0($0):p2align=0
+; CHECK-NEXT:    i32.load16_u $push6=, 0($1):p2align=0
+; CHECK-NEXT:    i32.xor $push8=, $pop7, $pop6
+; CHECK-NEXT:    i32.const $push0=, 2
+; CHECK-NEXT:    i32.add $push3=, $0, $pop0
+; CHECK-NEXT:    i32.load8_u $push4=, 0($pop3)
+; CHECK-NEXT:    i32.const $push13=, 2
+; CHECK-NEXT:    i32.add $push1=, $1, $pop13
+; CHECK-NEXT:    i32.load8_u $push2=, 0($pop1)
+; CHECK-NEXT:    i32.xor $push5=, $pop4, $pop2
+; CHECK-NEXT:    i32.or $push9=, $pop8, $pop5
+; CHECK-NEXT:    i32.const $push10=, 65535
+; CHECK-NEXT:    i32.and $push11=, $pop9, $pop10
+; CHECK-NEXT:    i32.eqz $push12=, $pop11
+; CHECK-NEXT:    return $pop12
+  %cmp_3 = call i32 @memcmp(ptr %a, ptr %b, i32 3)
+  %res = icmp eq i32 %cmp_3, 0
+  ret i1 %res
+}
+
+define i1 @memcmp_expand_5(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_5:
+; CHECK:         .functype memcmp_expand_5 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    i32.load $push7=, 0($0):p2align=0
+; CHECK-NEXT:    i32.load $push6=, 0($1):p2align=0
+; CHECK-NEXT:    i32.xor $push8=, $pop7, $pop6
+; CHECK-NEXT:    i32.const $push0=, 4
+; CHECK-NEXT:    i32.add $push3=, $0, $pop0
+; CHECK-NEXT:    i32.load8_u $push4=, 0($pop3)
+; CHECK-NEXT:    i32.const $push11=, 4
+; CHECK-NEXT:    i32.add $push1=, $1, $pop11
+; CHECK-NEXT:    i32.load8_u $push2=, 0($pop1)
+; CHECK-NEXT:    i32.xor $push5=, $pop4, $pop2
+; CHECK-NEXT:    i32.or $push9=, $pop8, $pop5
+; CHECK-NEXT:    i32.eqz $push10=, $pop9
+; CHECK-NEXT:    return $pop10
+  %cmp_5 = call i32 @memcmp(ptr %a, ptr %b, i32 5)
+  %res = icmp eq i32 %cmp_5, 0
+  ret i1 %res
+}
+
+define i1 @memcmp_expand_7(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_7:
+; CHECK:         .functype memcmp_expand_7 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    block
+; CHECK-NEXT:    block
+; CHECK-NEXT:    i32.load $push7=, 0($0):p2align=0
+; CHECK-NEXT:    i32.load $push6=, 0($1):p2align=0
+; CHECK-NEXT:    i32.xor $push8=, $pop7, $pop6
+; CHECK-NEXT:    i32.const $push0=, 4
+; CHECK-NEXT:    i32.add $push3=, $0, $pop0
+; CHECK-NEXT:    i32.load16_u $push4=, 0($pop3):p2align=0
+; CHECK-NEXT:    i32.const $push17=, 4
+; CHECK-NEXT:    i32.add $push1=, $1, $pop17
+; CHECK-NEXT:    i32.load16_u $push2=, 0($pop1):p2align=0
+; CHECK-NEXT:    i32.xor $push5=, $pop4, $pop2
+; CHECK-NEXT:    i32.or $push9=, $pop8, $pop5
+; CHECK-NEXT:    br_if 0, $pop9 # 0: down to label1
+; CHECK-NEXT:  # %bb.1: # %loadbb1
+; CHECK-NEXT:    i32.const $2=, 0
+; CHECK-NEXT:    i32.const $push10=, 6
+; CHECK-NEXT:    i32.add $push13=, $0, $pop10
+; CHECK-NEXT:    i32.load8_u $push14=, 0($pop13)
+; CHECK-NEXT:    i32.const $push18=, 6
+; CHECK-NEXT:    i32.add $push11=, $1, $pop18
+; CHECK-NEXT:    i32.load8_u $push12=, 0($pop11)
+; CHECK-NEXT:    i32.eq $push15=, $pop14, $pop12
+; CHECK-NEXT:    br_if 1, $pop15 # 1: down to label0
+; CHECK-NEXT:  .LBB2_2: # %res_block
+; CHECK-NEXT:    end_block # label1:
+; CHECK-NEXT:    i32.const $2=, 1
+; CHECK-NEXT:  .LBB2_3: # %endblock
+; CHECK-NEXT:    end_block # label0:
+; CHECK-NEXT:    i32.eqz $push16=, $2
+; CHECK-NEXT:    return $pop16
+  %cmp_7 = call i32 @memcmp(ptr %a, ptr %b, i32 7)
+  %res = icmp eq i32 %cmp_7, 0
+  ret i1 %res
+}
+
+define i1 @memcmp_expand_2(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_2:
+; CHECK:         .functype memcmp_expand_2 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    i32.load16_u $push1=, 0($0):p2align=0
+; CHECK-NEXT:    i32.load16_u $push0=, 0($1):p2align=0
+; CHECK-NEXT:    i32.eq $push2=, $pop1, $pop0
+; CHECK-NEXT:    return $pop2
+  %cmp_2 = call i32 @memcmp(ptr %a, ptr %b, i32 2)
+  %res = icmp eq i32 %cmp_2, 0
+  ret i1 %res
+}
+
+
+define i1 @memcmp_expand_8(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_8:
+; CHECK:         .functype memcmp_expand_8 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    i64.load $push1=, 0($0):p2align=0
+; CHECK-NEXT:    i64.load $push0=, 0($1):p2align=0
+; CHECK-NEXT:    i64.eq $push2=, $pop1, $pop0
+; CHECK-NEXT:    return $pop2
+  %cmp_8 = call i32 @memcmp(ptr %a, ptr %b, i32 8)
+  %res = icmp eq i32 %cmp_8, 0
+  ret i1 %res
+}
+
+
+define i1 @memcmp_expand_16(ptr %a, ptr %b) {
+; CHECK-LABEL: memcmp_expand_16:
+; CHECK:         .functype memcmp_expand_16 (i32, i32) -> (i32)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    i64.load $push7=, 0($0):p2align=0
+; CHECK-NEXT:    i64.load $push6=, 0($1):p2align=0
+; CHECK-NEXT:    i64.xor $push8=, $pop7, $pop6
+; CHECK-NEXT:    i32.const $push0=, 8
+; CHECK-NEXT:    i32.add $push3=, $0, $pop0
+; CHECK-NEXT:    i64.load $push4=, 0($pop3):p2align=0
+; CHECK-NEXT:    i32.const $push11=, 8
+; CHECK-NEXT:    i32.add $push1=, $1, $pop11
+; CHECK-NEXT:    i64.load $push2=, 0($pop1):p2align=0
+; CHECK-NEXT:    i64.xor $push5=, $pop4, $pop2
+; CHECK-NEXT:    i64.or $push9=, $pop8, $pop5
+; CHECK-NEXT:    i64.eqz $push10=, $pop9
+; CHECK-NEXT:    return $pop10
+  %cmp_16 = call i32 @memcmp(ptr %a, ptr %b, i32 16)
+  %res = icmp eq i32 %cmp_16, 0
+  ret i1 %res
+}
+
+
+
+

badumbatish · 2025-07-11T21:20:08Z

@lukel97 hi Luke! would love your review :)

llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp

llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp

llvm/test/CodeGen/WebAssembly/memcmp-expand.ll

github-actions · 2025-07-17T02:09:27Z

✅ With the latest revision this PR passed the C/C++ code formatter.

badumbatish added 2 commits July 11, 2025 14:14

Precommit test for memcmp expansion

e89afdc

[WASM] Expand memcmp for small size

d5103f6

llvmbot added the backend:WebAssembly label Jul 11, 2025

dschuff reviewed Jul 11, 2025

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llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp Show resolved Hide resolved

llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp Show resolved Hide resolved

lukel97 reviewed Jul 12, 2025

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llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp Outdated Show resolved Hide resolved

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llvm/test/CodeGen/WebAssembly/memcmp-expand.ll Outdated Show resolved Hide resolved

badumbatish added 2 commits July 13, 2025 07:09

Add more test for comparison against 8/4 options

3dd1cd7

Change to 8/4 load option with new NumLoadPerBlock

9407414

badumbatish changed the title ~~[WASM] Add support for memcmp expansion~~ [WebAssembly] Add support for memcmp expansion Jul 13, 2025

badumbatish mentioned this pull request Jul 17, 2025

[WebAssembly] Teach backend that loadv128 is good under -msimd #149230

Open

Added TODO for simd128 memcmp expansion

f5e27a8

Fix formatting issue

3509d9b

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