[llvm] [WASM] Add support for memcmp expansion (PR #148298)

[Luke Lau via llvm-commits]

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@@ -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)
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lukel97 wrote:

Can we add a negative test for a memcmp that is too large to be expanded?

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