[CodeGen] Allow mempcy/memset to generate small overlapping stores.

Summary:
All targets either just return false here or properly model `Fast`, so I
don't think there is any reason to prevent CodeGen from doing the right
thing here.

Subscribers: nemanjai, javed.absar, eraman, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D55365

llvm-svn: 348843

1 files changed, 3 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 01364944b22..b9afcc13b3d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5395,12 +5395,10 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
 
       // If the new VT cannot cover all of the remaining bits, then consider
       // issuing a (or a pair of) unaligned and overlapping load / store.
-      // FIXME: Only does this for 64-bit or more since we don't have proper
-      // cost model for unaligned load / store.
       bool Fast;
-      if (NumMemOps && AllowOverlap &&
-          VTSize >= 8 && NewVTSize < Size &&
-          TLI.allowsMisalignedMemoryAccesses(VT, DstAS, DstAlign, &Fast) && Fast)
+      if (NumMemOps && AllowOverlap && NewVTSize < Size &&
+          TLI.allowsMisalignedMemoryAccesses(VT, DstAS, DstAlign, &Fast) &&
+          Fast)
         VTSize = Size;
       else {
         VT = NewVT;