From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 19 Jun 2008 06:09:51 +0000 (+0000)
Subject: Fix a bug with <8 x i16> shuffle lowering on X86 where parts of the
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=2c8e64d3e4a3daca9ec74c617a518d03d33eee90;p=oota-llvm.git

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 4211508225f..79629240b35 100644
--- 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
index 00000000000..ba0a1f90ab9
--- /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
+}
+