[CodeGen][ExpandMemcmp] Allow memcmp to expand to vector loads (2).

 - Targets that want to support memcmp expansions now return the list of
   supported load sizes.
 - Expansion codegen does not assume that all power-of-two load sizes
   smaller than the max load size are valid. For examples, this is not the
   case for x86(32bit)+sse2.

Fixes PR34887.

llvm-svn: 316905

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/MergeICmps.cpp b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
index 1244a9776fa..f4de036059e 100644
--- a/llvm/lib/Transforms/Scalar/MergeICmps.cpp
+++ b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
@@ -625,8 +625,7 @@ PreservedAnalyses MergeICmps::runImpl(Function &F, const TargetLibraryInfo *TLI,
 
   // We only try merging comparisons if the target wants to expand memcmp later.
   // The rationale is to avoid turning small chains into memcmp calls.
-  unsigned MaxLoadSize;
-  if (!TTI->enableMemCmpExpansion(MaxLoadSize)) return PreservedAnalyses::all();
+  if (!TTI->enableMemCmpExpansion(true)) return PreservedAnalyses::all();
 
   bool MadeChange = false;