From 4e8fcbd3fd6f64d43dbebc6fa6b29dfa4143eddf Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Thu, 7 Aug 2014 10:37:35 +0000
Subject: [PATCH] [x86] Fix another miscompile found through fuzz testing the
 new vector shuffle lowering.

This is closely related to the previous one. Here we failed to use the
source offset when swapping in the other case -- where we end up
swapping the *final* shuffle. The cause of this bug is a bit different:
I simply wasn't thinking about the fact that this mask is actually
a slice of a wide mask and thus has numbers that need SourceOffset
applied. Simple fix. Would be even more simple with an algorithm-y thing
to use here, but correctness first. =]

llvm-svn: 215095
---
 llvm/lib/Target/X86/X86ISelLowering.cpp        |  8 ++++----
 llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll | 17 +++++++++++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index d85ac5e55e43..c62c2fd5f358 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -7546,10 +7546,10 @@ static SDValue lowerV8I16SingleInputVectorShuffle(
           // We also have to update the final source mask in this case because
           // it may need to undo the above swap.
           for (int &M : FinalSourceHalfMask)
-            if (M == (InputsFixed[0] ^ 1))
-              M = InputsFixed[1];
-            else if (M == InputsFixed[1])
-              M = InputsFixed[0] ^ 1;
+            if (M == (InputsFixed[0] ^ 1) + SourceOffset)
+              M = InputsFixed[1] + SourceOffset;
+            else if (M == InputsFixed[1] + SourceOffset)
+              M = InputsFixed[0] ^ 1 + SourceOffset;
 
           InputsFixed[1] = InputsFixed[0] ^ 1;
         }
diff --git a/llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll b/llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
index 5c6a4dbaa4b9..5d0509f45cad 100644
--- a/llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
+++ b/llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
@@ -238,6 +238,23 @@ define <8 x i16> @shuffle_v8i16_66751643(<8 x i16> %a, <8 x i16> %b) {
   ret <8 x i16> %shuffle
 }
 
+define <8 x i16> @shuffle_v8i16_60514754(<8 x i16> %a, <8 x i16> %b) {
+; SSE2-LABEL: @shuffle_v8i16_60514754
+; SSE2:       # BB#0:
+; SSE2-NEXT:    pshufhw {{.*}} # xmm0 = xmm0[0,1,2,3,6,5,4,7]
+; SSE2-NEXT:    pshufd {{.*}} # xmm0 = xmm0[0,2,2,3]
+; SSE2-NEXT:    pshuflw {{.*}} # xmm0 = xmm0[2,0,3,1,4,5,6,7]
+; SSE2-NEXT:    pshufhw {{.*}} # xmm0 = xmm0[0,1,2,3,6,7,5,6]
+; SSE2-NEXT:    retq
+;
+; SSSE3-LABEL: @shuffle_v8i16_60514754
+; SSSE3:       # BB#0:
+; SSSE3-NEXT:    pshufb {{.*}} # xmm0 = xmm0[12,13,0,1,10,11,2,3,8,9,14,15,10,11,8,9]
+; SSSE3-NEXT:    retq
+  %shuffle = shufflevector <8 x i16> %a, <8 x i16> undef, <8 x i32> <i32 6, i32 0, i32 5, i32 1, i32 4, i32 7, i32 5, i32 4>
+  ret <8 x i16> %shuffle
+}
+
 define <8 x i16> @shuffle_v8i16_00444444(<8 x i16> %a, <8 x i16> %b) {
 ; SSE2-LABEL: @shuffle_v8i16_00444444
 ; SSE2:       # BB#0: