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[WebAssembly] Add support for memcmp expansion #148298

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Merged
badumbatish merged 8 commits into from
Jul 20, 2025
Merged

[WebAssembly] Add support for memcmp expansion #148298

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e89afdc
Precommit test for memcmp expansion
badumbatish Jul 11, 2025
d5103f6
[WASM] Expand memcmp for small size
badumbatish Jul 11, 2025
3dd1cd7
Add more test for comparison against 8/4 options
badumbatish Jul 13, 2025
9407414
Change to 8/4 load option with new NumLoadPerBlock
badumbatish Jul 13, 2025
f5e27a8
Added TODO for simd128 memcmp expansion
badumbatish Jul 17, 2025
3509d9b
Fix formatting issue
badumbatish Jul 17, 2025
fe3b7dc
Merge branch 'main' into wasm_memcmp_expansion
badumbatish Jul 20, 2025
8a8c153
Addresses nit in PR
badumbatish Jul 20, 2025
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Addresses nit in PR
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@badumbatish
badumbatish committed Jul 20, 2025
commit 8a8c1533cf3534330f91582a6e94f019c531bb6a
2 changes: 0 additions & 2 deletions llvm/lib/Target/WebAssembly/WebAssemblyTargetTransformInfo.cpp
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Expand Up @@ -148,8 +148,6 @@ WebAssemblyTTIImpl::enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const {
Options.AllowOverlappingLoads = true;

// TODO: Teach WebAssembly backend about load v128.
// if (ST->hasSIMD128())
// Options.LoadSizes.push_back(16);

Options.LoadSizes.append({8, 4, 2, 1});
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Options.MaxNumLoads = TLI->getMaxExpandSizeMemcmp(OptSize);
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19 changes: 13 additions & 6 deletions llvm/test/CodeGen/WebAssembly/memcmp-expand.ll
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@@ -1,5 +1,5 @@
; 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 -mattr=+simd128 | FileCheck %s
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s

target triple = "wasm32-unknown-unknown"

Expand Down Expand Up @@ -101,6 +101,18 @@ define i1 @memcmp_expand_2(ptr %a, ptr %b) {
ret i1 %res
}

define i1 @memcmp_expand_2_align(ptr align(2) %a, ptr align(2) %b) {
; CHECK-LABEL: memcmp_expand_2_align:
; CHECK: .functype memcmp_expand_2_align (i32, i32) -> (i32)
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: i32.load16_u $push1=, 0($0)
; CHECK-NEXT: i32.load16_u $push0=, 0($1)
; 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:
Expand All @@ -115,7 +127,6 @@ define i1 @memcmp_expand_8(ptr %a, ptr %b) {
ret i1 %res
}


; TODO: Should be using a single load i64x2 or equivalent in bitsizes
define i1 @memcmp_expand_16(ptr %a, ptr %b) {
; CHECK-LABEL: memcmp_expand_16:
Expand All @@ -138,7 +149,3 @@ define i1 @memcmp_expand_16(ptr %a, ptr %b) {
%res = icmp eq i32 %cmp_16, 0
ret i1 %res
}




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