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[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
This commit is contained in:
Chandler Carruth 2014-08-07 10:37:35 +00:00
parent e206385e99
commit 4e8fcbd3fd
2 changed files with 21 additions and 4 deletions
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8
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -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;
}

17
llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
View File

@ -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: