From 39fc1459953040a480e58142fb6adbfcc4082fe8 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Sat, 15 Apr 2006 03:13:24 +0000
Subject: [PATCH] Do not use movs{h|l}dup for a shuffle with a single non-undef
 node.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27718 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4d5b4da802e..409c39be5d2 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1724,12 +1724,14 @@ bool X86::isMOVSHDUPMask(SDNode *N) {
     return false;
 
   // Expect 1, 1, 3, 3
+  unsigned NumNodes = 0;
   for (unsigned i = 0; i < 2; ++i) {
     SDOperand Arg = N->getOperand(i);
     if (Arg.getOpcode() == ISD::UNDEF) continue;
     assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
     unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
     if (Val != 1) return false;
+    NumNodes++;
   }
   for (unsigned i = 2; i < 4; ++i) {
     SDOperand Arg = N->getOperand(i);
@@ -1737,8 +1739,12 @@ bool X86::isMOVSHDUPMask(SDNode *N) {
     assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
     unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
     if (Val != 3) return false;
+    NumNodes++;
   }
-  return true;
+
+  // Don't use movshdup if the resulting vector contains only one undef node.
+  // Use {p}shuf* instead.
+  return NumNodes > 1;
 }
 
 /// isMOVSLDUPMask - Return true if the specified VECTOR_SHUFFLE operand
@@ -1750,12 +1756,14 @@ bool X86::isMOVSLDUPMask(SDNode *N) {
     return false;
 
   // Expect 0, 0, 2, 2
+  unsigned NumNodes = 0;
   for (unsigned i = 0; i < 2; ++i) {
     SDOperand Arg = N->getOperand(i);
     if (Arg.getOpcode() == ISD::UNDEF) continue;
     assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
     unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
     if (Val != 0) return false;
+    NumNodes++;
   }
   for (unsigned i = 2; i < 4; ++i) {
     SDOperand Arg = N->getOperand(i);
@@ -1763,8 +1771,12 @@ bool X86::isMOVSLDUPMask(SDNode *N) {
     assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
     unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
     if (Val != 2) return false;
+    NumNodes++;
   }
-  return true;
+
+  // Don't use movsldup if the resulting vector contains only one undef node.
+  // Use {p}shuf* instead.
+  return NumNodes > 1;
 }
 
 /// isSplatMask - Return true if the specified VECTOR_SHUFFLE operand specifies
-- 
2.34.1