[X86][MMX] Improve support for folding fptosi from XMM to MMX

llvm-svn: 299338

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 567eae52236..57d8139acba 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -28969,6 +28969,16 @@ static SDValue combineBitcast(SDNode *N, SelectionDAG &DAG,
                          DAG.getBitcast(MVT::v2i64, N00));
   }
 
+  // Detect bitcasts from FP_TO_SINT to x86mmx.
+  if (VT == MVT::x86mmx && SrcVT == MVT::v2i32 &&
+      N0.getOpcode() == ISD::FP_TO_SINT) {
+    SDLoc DL(N0);
+    SDValue Res = DAG.getNode(ISD::CONCAT_VECTORS, DL, MVT::v4i32, N0,
+                              DAG.getUNDEF(MVT::v2i32));
+    return DAG.getNode(X86ISD::MOVDQ2Q, DL, VT,
+                       DAG.getBitcast(MVT::v2i64, Res));
+  }
+
   // Convert a bitcasted integer logic operation that has one bitcasted
   // floating-point operand into a floating-point logic operation. This may
   // create a load of a constant, but that is cheaper than materializing the