Fix an optimization involving EXTRACT_SUBVECTOR in DAGCombine so it behaves correctly. PR11494.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145996 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 35 insertions, 13 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 62c2c6ae6c..2824fdb886 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7181,19 +7181,23 @@ SDValue DAGCombiner::visitEXTRACT_SUBVECTOR(SDNode* N) {
     if (NVT != SmallVT || NVT.getSizeInBits()*2 != BigVT.getSizeInBits())
       return SDValue();
 
-    // Combine:
-    //    (extract_subvec (insert_subvec V1, V2, InsIdx), ExtIdx)
-    // Into:
-    //    indicies are equal => V1
-    //    otherwise => (extract_subvec V1, ExtIdx)
-    //
-    SDValue InsIdx = N->getOperand(1);
-    SDValue ExtIdx = V->getOperand(2);
-
-    if (InsIdx == ExtIdx)
-      return V->getOperand(1);
-    return DAG.getNode(ISD::EXTRACT_SUBVECTOR, N->getDebugLoc(), NVT,
-                       V->getOperand(0), N->getOperand(1));
+    // Only handle cases where both indexes are constants with the same type.
+    ConstantSDNode *InsIdx = dyn_cast<ConstantSDNode>(N->getOperand(1));
+    ConstantSDNode *ExtIdx = dyn_cast<ConstantSDNode>(V->getOperand(2));
+
+    if (InsIdx && ExtIdx &&
+        InsIdx->getValueType(0).getSizeInBits() <= 64 &&
+        ExtIdx->getValueType(0).getSizeInBits() <= 64) {
+      // Combine:
+      //    (extract_subvec (insert_subvec V1, V2, InsIdx), ExtIdx)
+      // Into:
+      //    indices are equal => V1
+      //    otherwise => (extract_subvec V1, ExtIdx)
+      if (InsIdx->getZExtValue() == ExtIdx->getZExtValue())
+        return V->getOperand(1);
+      return DAG.getNode(ISD::EXTRACT_SUBVECTOR, N->getDebugLoc(), NVT,
+                         V->getOperand(0), N->getOperand(1));
+    }
   }
 
   return SDValue();
diff --git a/test/CodeGen/X86/2011-12-06-AVXVectorExtractCombine.ll b/test/CodeGen/X86/2011-12-06-AVXVectorExtractCombine.ll
new file mode 100644
index 0000000000..fcaabddd2c
--- /dev/null
+++ b/test/CodeGen/X86/2011-12-06-AVXVectorExtractCombine.ll
@@ -0,0 +1,18 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=corei7-avx -mattr=+avx | FileCheck %s
+; PR11494
+
+define void @test(<4 x i32>* nocapture %p) nounwind {
+  ; CHECK: test:
+  ; CHECK: vpxor %xmm0, %xmm0, %xmm0
+  ; CHECK-NEXT: vpmaxsd {{.*}}, %xmm0, %xmm0
+  ; CHECK-NEXT: vmovdqu	%xmm0, (%rdi)
+  ; CHECK-NEXT: ret
+  %a = call <4 x i32> @llvm.x86.sse41.pmaxsd(<4 x i32> <i32 -8, i32 -9, i32 -10, i32 -11>, <4 x i32> zeroinitializer) nounwind
+  %b = shufflevector <4 x i32> %a, <4 x i32> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 undef, i32 0, i32 1, i32 2, i32 3>
+  %c = shufflevector <8 x i32> %b, <8 x i32> undef, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+  store <4 x i32> %c, <4 x i32>* %p, align 1
+  ret void
+}
+
+declare <4 x i32> @llvm.x86.sse41.pminsd(<4 x i32>, <4 x i32>) nounwind readnone
+declare <4 x i32> @llvm.x86.sse41.pmaxsd(<4 x i32>, <4 x i32>) nounwind readnone