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[x86] Tighten the assertions to document that canonicalization has 

actually removed all but a *very* small number of choices for v2i64.
Also remove dead code handling cases that simply cannot arise.

llvm-svn: 229670
This commit is contained in:
Chandler Carruth 2015-02-18 11:46:29 +00:00
parent 811f0ee8c1
commit bbb377c3a1
1 changed files with 5 additions and 4 deletions
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9
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -8618,8 +8618,10 @@ static SDValue lowerV2I64VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
DAG.getNode(X86ISD::PSHUFD, SDLoc(Op), MVT::v4i32, V1,
getV4X86ShuffleImm8ForMask(WidenedMask, DAG)));
}
assert((Mask[0] >= 2) + (Mask[1] >= 2) == 1 &&
"Canonicalization ensures we only see shuffles with two inputs.");
assert(Mask[0] != -1 && "No undef lanes in multi-input v2 shuffles!");
assert(Mask[1] != -1 && "No undef lanes in multi-input v2 shuffles!");
assert(Mask[0] < 2 && "We sort V1 to be the first input.");
assert(Mask[1] >= 2 && "We sort V2 to be the second input.");
// Try to use shift instructions.
if (SDValue Shift =
@ -8633,8 +8635,7 @@ static SDValue lowerV2I64VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
return Insertion;
// Try inverting the insertion since for v2 masks it is easy to do and we
// can't reliably sort the mask one way or the other.
int InverseMask[2] = {Mask[0] < 0 ? -1 : (Mask[0] ^ 2),
Mask[1] < 0 ? -1 : (Mask[1] ^ 2)};
int InverseMask[2] = {Mask[0] ^ 2, Mask[1] ^ 2};
if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
MVT::v2i64, DL, V2, V1, InverseMask, Subtarget, DAG))
return Insertion;