[ARM] Enable vector extload combine for legal types.

This commit enables forming vector extloads for ARM.
It only does so for legal types, and when we can't fold the extension
in a wide/long form of the user instruction.

Enabling it for larger types isn't as good an idea on ARM as it is on
X86, because: 
- we pretend that extloads are legal, but end up generating vld+vmov
- we have instructions like vld {dN, dM}, which can't be generated
  when we "manually expand" extloads to vld+vmov.

For legal types, the combine doesn't fire that often: in the
integration tests only in a big endian testcase, where it removes a
pointless AND.

Related to rdar://19723053
Differential Revision: http://reviews.llvm.org/D7423

llvm-svn: 231396

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index 7fd2725b7e5..6977862fe35 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -283,6 +283,8 @@ namespace llvm {
     using TargetLowering::isZExtFree;
     bool isZExtFree(SDValue Val, EVT VT2) const override;
 
+    bool isVectorLoadExtDesirable(SDValue ExtVal) const override;
+
     bool allowTruncateForTailCall(Type *Ty1, Type *Ty2) const override;