[PPC] Give unaligned memory access lower cost on processor that supports it
Newer ppc supports unaligned memory access, it reduces the cost of unaligned memory access significantly. This patch handles this case in PPCTTIImpl::getMemoryOpCost.
This patch fixes pr31492.
Differential Revision: https://reviews.llvm.org/D28630
This is resubmit of r292680, which was reverted by r293092. The internal application failures were actually caused by a source code bug.
llvm-svn: 295506
diff --git a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
index f94d1ea..2f1bcea 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
@@ -401,6 +401,10 @@
if (IsVSXType || (ST->hasVSX() && IsAltivecType))
return Cost;
+ // Newer PPC supports unaligned memory access.
+ if (TLI->allowsMisalignedMemoryAccesses(LT.second, 0))
+ return Cost;
+
// PPC in general does not support unaligned loads and stores. They'll need
// to be decomposed based on the alignment factor.