In the case of an extractelement on an insertelement value,

the element indices may be equal if either one is not a
constant.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63311 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 30 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index ab2c832300..16f17e56f4 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2597,9 +2597,13 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, MVT VT,
     // EXTRACT_VECTOR_ELT of INSERT_VECTOR_ELT is often formed when vector
     // operations are lowered to scalars.
     if (N1.getOpcode() == ISD::INSERT_VECTOR_ELT) {
+      // If the indices are the same, return the inserted element.
       if (N1.getOperand(2) == N2)
         return N1.getOperand(1);
-      else
+      // If the indices are known different, extract the element from
+      // the original vector.
+      else if (isa<ConstantSDNode>(N1.getOperand(2)) &&
+               isa<ConstantSDNode>(N2))
         return getNode(ISD::EXTRACT_VECTOR_ELT, VT, N1.getOperand(0), N2);
     }
     break;
diff --git a/test/CodeGen/X86/vec_ins_extract-1.ll b/test/CodeGen/X86/vec_ins_extract-1.ll
new file mode 100644
index 0000000000..44ae039384
--- /dev/null
+++ b/test/CodeGen/X86/vec_ins_extract-1.ll
@@ -0,0 +1,25 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep {(%esp,%eax,4)} | count 4
+
+; Inserts and extracts with variable indices must be lowered
+; to memory accesses.
+
+define i32 @t0(i32 inreg %t7, <4 x i32> inreg %t8) nounwind {
+  %t13 = insertelement <4 x i32> %t8, i32 76, i32 %t7
+  %t9 = extractelement <4 x i32> %t13, i32 0
+  ret i32 %t9
+}
+define i32 @t1(i32 inreg %t7, <4 x i32> inreg %t8) nounwind {
+  %t13 = insertelement <4 x i32> %t8, i32 76, i32 0
+  %t9 = extractelement <4 x i32> %t13, i32 %t7
+  ret i32 %t9
+}
+define <4 x i32> @t2(i32 inreg %t7, <4 x i32> inreg %t8) nounwind {
+  %t9 = extractelement <4 x i32> %t8, i32 %t7
+  %t13 = insertelement <4 x i32> %t8, i32 %t9, i32 0
+  ret <4 x i32> %t13
+}
+define <4 x i32> @t3(i32 inreg %t7, <4 x i32> inreg %t8) nounwind {
+  %t9 = extractelement <4 x i32> %t8, i32 0
+  %t13 = insertelement <4 x i32> %t8, i32 %t9, i32 %t7
+  ret <4 x i32> %t13
+}