[llvm-branch-commits] [llvm] [RISCV] Add initial support of memcmp expansion (PR #107548)

[Craig Topper via llvm-branch-commits]

================
@@ -2113,3 +2113,17 @@ bool RISCVTTIImpl::shouldConsiderAddressTypePromotion(
   }
   return Considerable;
 }
+
+RISCVTTIImpl::TTI::MemCmpExpansionOptions
+RISCVTTIImpl::enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const {
+  TTI::MemCmpExpansionOptions Options;
+  // FIXME: Vector haven't been tested.
+  Options.AllowOverlappingLoads =
+      (ST->enableUnalignedScalarMem() || ST->enableUnalignedVectorMem());
+  Options.MaxNumLoads = TLI->getMaxExpandSizeMemcmp(OptSize);
+  Options.NumLoadsPerBlock = Options.MaxNumLoads;
+  if (ST->is64Bit())
----------------
topperc wrote:

I wonder if this might be better

```
if (ST->is64Bit())
  Options.LoadSize = {8, 4, 2, 1};
else
  Options.LoadSize = {4, 2, 1};
```

https://github.com/llvm/llvm-project/pull/107548