[X86] Add a check for 'isMOVHLPSMask' within method 'isShuffleMaskLegal'.

Before this change, method 'isShuffleMaskLegal' didn't know that shuffles
implementing a 'movhlps' operation were perfectly legal for SSE targets.

This patch adds the missing check for 'isMOVHLPSMask' inside method
'isShuffleMaskLegal' to fix the problem.

The reason why it is important to do this is because the DAGCombiner
conservatively avoids combining a pair of shuffles if the resulting shuffle
node has an illegal mask. Before this patch, shuffles with a MOVHLPS mask were
wrongly considered not to be legal. This was the root cause of some poor-code
generation bugs.

llvm-svn: 213137

3 files changed, 35 insertions, 26 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index c7440136255..6f876b5aafe 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -16880,6 +16880,7 @@ X86TargetLowering::isShuffleMaskLegal(const SmallVectorImpl<int> &M,
   return (SVT.getVectorNumElements() == 2 ||
           ShuffleVectorSDNode::isSplatMask(&M[0], VT) ||
           isMOVLMask(M, SVT) ||
+          isMOVHLPSMask(M, SVT) ||
           isSHUFPMask(M, SVT) ||
           isPSHUFDMask(M, SVT) ||
           isPSHUFHWMask(M, SVT, Subtarget->hasInt256()) ||
diff --git a/llvm/test/CodeGen/X86/combine-vec-shuffle-3.ll b/llvm/test/CodeGen/X86/combine-vec-shuffle-3.ll
index d966d7efdd1..c2cff517d4e 100644
--- a/llvm/test/CodeGen/X86/combine-vec-shuffle-3.ll
+++ b/llvm/test/CodeGen/X86/combine-vec-shuffle-3.ll
@@ -35,14 +35,10 @@ define <4 x float> @test4(<4 x float> %a, <4 x float> %b) {
   %2 = shufflevector <4 x float> %1, <4 x float> %b, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
   ret <4 x float> %2
 }
-; FIXME: this should be lowered as a single movhlps. However, the backend
-; wrongly thinks that shuffle mask [6,7,2,3] is not legal. Therefore, we
-; end up with the sub-optimal sequence 'shufps, palignr'.
 ; CHECK-LABEL: test4
 ; Mask: [6,7,2,3]
-; CHECK: shufps $94
-; CHECK: palignr $8
-; CHECK: ret
+; CHECK: movhlps
+; CHECK-NEXT: ret
 
 define <4 x float> @test5(<4 x float> %a, <4 x float> %b) {
   %1 = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 4, i32 1, i32 6, i32 3>
@@ -90,13 +86,10 @@ define <4 x i32> @test9(<4 x i32> %a, <4 x i32> %b) {
   %2 = shufflevector <4 x i32> %1, <4 x i32> %b, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
   ret <4 x i32> %2
 }
-; FIXME: this should be lowered as a single movhlps. However, the backend thinks that
-; shuffle mask [6,7,2,3] is not legal.
 ; CHECK-LABEL: test9
 ; Mask: [6,7,2,3]
-; CHECK: shufps $94
-; CHECK: palignr $8
-; CHECK: ret
+; CHECK: movhlps
+; CHECK-NEXT: ret
 
 define <4 x i32> @test10(<4 x i32> %a, <4 x i32> %b) {
   %1 = shufflevector <4 x i32> %a, <4 x i32> %b, <4 x i32> <i32 4, i32 1, i32 6, i32 3>
@@ -144,13 +137,9 @@ define <4 x float> @test14(<4 x float> %a, <4 x float> %b) {
   %2 = shufflevector <4 x float> %1, <4 x float> %a, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
   ret <4 x float> %2
 }
-; FIXME: this should be lowered as a single movhlps. However, the backend
-; wrongly thinks that shuffle mask [6,7,2,3] is not legal. Therefore, we
-; end up with the sub-optimal sequence 'pshufd, palignr'.
 ; CHECK-LABEL: test14
 ; Mask: [6,7,2,3]
-; CHECK: pshufd $94
-; CHECK: palignr $8
+; CHECK: movhlps
 ; CHECK: ret
 
 define <4 x float> @test15(<4 x float> %a, <4 x float> %b) {
@@ -199,13 +188,9 @@ define <4 x i32> @test19(<4 x i32> %a, <4 x i32> %b) {
   %2 = shufflevector <4 x i32> %1, <4 x i32> %a, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
   ret <4 x i32> %2
 }
-; FIXME: this should be lowered as a single movhlps. However, the backend
-; wrongly thinks that shuffle mask [6,7,2,3] is not legal. Therefore, we
-; end up with the sub-optimal sequence 'shufps, palignr'.
 ; CHECK-LABEL: test19
 ; Mask: [6,7,2,3]
-; CHECK: pshufd $94
-; CHECK: palignr $8
+; CHECK: movhlps
 ; CHECK: ret
 
 define <4 x i32> @test20(<4 x i32> %a, <4 x i32> %b) {
@@ -371,3 +356,30 @@ define <4 x float> @blend_123(<4 x float> %a, <4 x float> %b) {
 ; CHECK: movss
 ; CHECK: ret
 
+define <4 x i32> @test_movhl_1(<4 x i32> %a, <4 x i32> %b) {
+  %1 = shufflevector <4 x i32> %a, <4 x i32> %b, <4 x i32> <i32 2, i32 7, i32 5, i32 3>
+  %2 = shufflevector <4 x i32> %1, <4 x i32> %b, <4 x i32> <i32 6, i32 1, i32 0, i32 3>
+  ret <4 x i32> %2
+}
+; CHECK-LABEL: test_movhl_1
+; CHECK: movhlps
+; CHECK-NEXT: ret
+
+define <4 x i32> @test_movhl_2(<4 x i32> %a, <4 x i32> %b) {
+  %1 = shufflevector <4 x i32> %a, <4 x i32> %b, <4 x i32> <i32 2, i32 0, i32 3, i32 6>
+  %2 = shufflevector <4 x i32> %1, <4 x i32> %b, <4 x i32> <i32 3, i32 7, i32 0, i32 2>
+  ret <4 x i32> %2
+}
+; CHECK-LABEL: test_movhl_2
+; CHECK: movhlps
+; CHECK-NEXT: ret
+
+define <4 x i32> @test_movhl_3(<4 x i32> %a, <4 x i32> %b) {
+  %1 = shufflevector <4 x i32> %a, <4 x i32> %b, <4 x i32> <i32 7, i32 6, i32 3, i32 2>
+  %2 = shufflevector <4 x i32> %1, <4 x i32> %b, <4 x i32> <i32 6, i32 0, i32 3, i32 2>
+  ret <4 x i32> %2
+}
+; CHECK-LABEL: test_movhl_3
+; CHECK: movhlps
+; CHECK-NEXT: ret
+
diff --git a/llvm/test/CodeGen/X86/combine-vec-shuffle-4.ll b/llvm/test/CodeGen/X86/combine-vec-shuffle-4.ll
index 45c624a61d4..6ca45920c80 100644
--- a/llvm/test/CodeGen/X86/combine-vec-shuffle-4.ll
+++ b/llvm/test/CodeGen/X86/combine-vec-shuffle-4.ll
@@ -38,14 +38,10 @@ define <4 x float> @test4(<4 x float> %a, <4 x float> %b) {
   %2 = shufflevector <4 x float> %1, <4 x float> %b, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
   ret <4 x float> %2
 }
-; FIXME: this should be lowered as a single movhlps. However, the backend
-; wrongly thinks that shuffle mask [6,7,2,3] is not legal. Therefore, we
-; end up with the sub-optimal sequence 'movhlps, palignr'.
 ; CHECK-LABEL: test4
 ; Mask: [6,7,2,3]
 ; CHECK: movhlps
-; CHECK: palignr $8
-; CHECK: ret
+; CHECK-NEXT: ret
 
 define <4 x float> @test5(<4 x float> %a, <4 x float> %b) {
   %1 = shufflevector <4 x float> %a, <4 x float> undef, <4 x i32> <i32 0, i32 4, i32 1, i32 3>