Fix a bug with <8 x i16> shuffle lowering on X86 where parts of the

shuffle could be skipped.  The check is invalid because the loop index i
doesn't correspond to the element actually inserted. The correct check is
already done a few lines earlier, for whether the element is already in
the right spot, so this shouldn't have any effect on the codegen for
code that was already correct.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52486 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4211508225fec7a05bdee80e02ca3bf2ff24cb9f..79629240b3534143ef516d99b0d885e8dfc8b540 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -3445,8 +3445,6 @@ SDOperand LowerVECTOR_SHUFFLEv8i16(SDOperand V1, SDOperand V2,
         continue;
       SDOperand Elt = MaskElts[i];
       unsigned EltIdx = cast<ConstantSDNode>(Elt)->getValue();
-      if (EltIdx == i)
-        continue;
       SDOperand ExtOp = (EltIdx < 8)
         ? DAG.getNode(ISD::EXTRACT_VECTOR_ELT, MVT::i16, V1,
                       DAG.getConstant(EltIdx, PtrVT))

diff --git a/test/CodeGen/X86/2008-06-18-BadShuffle.ll b/test/CodeGen/X86/2008-06-18-BadShuffle.ll
new file mode 100644 (file)
index 0000000..ba0a1f9
--- /dev/null
+++ b/test/CodeGen/X86/2008-06-18-BadShuffle.ll
@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | llc -march=x86 -mcpu=i386 -mattr=+sse2 | grep pinsrw
+
+; Test to make sure we actually insert the bottom element of the vector
+define <8 x i16> @a(<8 x i16> %a) nounwind  {
+entry:
+       shufflevector <8 x i16> %a, <8 x i16> zeroinitializer, <8 x i32> < i32 0, i32 8, i32 8, i32 8, i32 8, i32 8, i32 8, i32 8 >
+       %add = add <8 x i16> %0, %a
+       ret <8 x i16> %add
+}
+