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

[Luke Lau via llvm-commits]

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@@ -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;
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lukel97 wrote:

AArch64 + RISC-V just set this to Options.MaxNumPerLoads, which I guess just means maximum 1 expansion per block? We can probably follow suit here

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