X86 MMX: optimize transfer from mmx to i32
We used to generate a store (movq) + a load.
Now we use movd.
rdar://9946746
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167056 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4b6ab74..ce9b0a8 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -14399,6 +14399,14 @@
return NewOp;
SDValue InputVector = N->getOperand(0);
+ // Detect whether we are trying to convert from mmx to i32 and the bitcast
+ // from mmx to v2i32 has a single usage.
+ if (InputVector.getNode()->getOpcode() == llvm::ISD::BITCAST &&
+ InputVector.getNode()->getOperand(0).getValueType() == MVT::x86mmx &&
+ InputVector.hasOneUse() && N->getValueType(0) == MVT::i32)
+ return DAG.getNode(X86ISD::MMX_MOVD2W, InputVector.getDebugLoc(),
+ N->getValueType(0),
+ InputVector.getNode()->getOperand(0));
// Only operate on vectors of 4 elements, where the alternative shuffling
// gets to be more expensive.