From 07ccae240aafe2c732c47404a4e9d9dba6e4be78 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sun, 2 Apr 2017 17:45:41 +0000
Subject: [PATCH] [X86][MMX] Improve support for folding fptosi from XMM to MMX

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299338 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 10 ++++++++++
 test/CodeGen/X86/mmx-cvt.ll        | 10 +++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 567eae52236..57d8139acba 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/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
diff --git a/test/CodeGen/X86/mmx-cvt.ll b/test/CodeGen/X86/mmx-cvt.ll
index 80876a87de7..8f2da953539 100644
--- a/test/CodeGen/X86/mmx-cvt.ll
+++ b/test/CodeGen/X86/mmx-cvt.ll
@@ -83,11 +83,9 @@ define void @fptosi_v2f64_v2i32(<2 x double>, <1 x i64>*) nounwind {
 ; X86-NEXT:    pushl %ebp
 ; X86-NEXT:    movl %esp, %ebp
 ; X86-NEXT:    andl $-8, %esp
-; X86-NEXT:    subl $16, %esp
+; X86-NEXT:    subl $8, %esp
 ; X86-NEXT:    movl 8(%ebp), %eax
-; X86-NEXT:    cvttpd2dq %xmm0, %xmm0
-; X86-NEXT:    movlpd %xmm0, {{[0-9]+}}(%esp)
-; X86-NEXT:    movq {{[0-9]+}}(%esp), %mm0
+; X86-NEXT:    cvttpd2pi %xmm0, %mm0
 ; X86-NEXT:    paddd %mm0, %mm0
 ; X86-NEXT:    movq %mm0, (%esp)
 ; X86-NEXT:    movl (%esp), %ecx
@@ -100,9 +98,7 @@ define void @fptosi_v2f64_v2i32(<2 x double>, <1 x i64>*) nounwind {
 ;
 ; X64-LABEL: fptosi_v2f64_v2i32:
 ; X64:       # BB#0:
-; X64-NEXT:    cvttpd2dq %xmm0, %xmm0
-; X64-NEXT:    movlpd %xmm0, -{{[0-9]+}}(%rsp)
-; X64-NEXT:    movq -{{[0-9]+}}(%rsp), %mm0
+; X64-NEXT:    cvttpd2pi %xmm0, %mm0
 ; X64-NEXT:    paddd %mm0, %mm0
 ; X64-NEXT:    movq %mm0, (%rdi)
 ; X64-NEXT:    retq
-- 
2.40.0