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[x86] Fix a helper to reflect that what we actually care about is 

128-bit lane crossings, not 'half' crossings. This came up in code
review ages ago, but I hadn't really addresesd it. Also added some
documentation for the helper.

No functionality changed.

llvm-svn: 218203
This commit is contained in:
Chandler Carruth 2014-09-21 09:35:25 +00:00
parent 293327ddcd
commit a746d776eb
1 changed files with 12 additions and 9 deletions
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21
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -9106,13 +9106,16 @@ static SDValue lower128BitVectorShuffle(SDValue Op, SDValue V1, SDValue V2,
}
}
static bool isHalfCrossingShuffleMask(ArrayRef<int> Mask) {
/// \brief Test whether there are elements crossing 128-bit lanes in this
/// shuffle mask.
///
/// X86 divides up its shuffles into in-lane and cross-lane shuffle operations
/// and we routinely test for these.
static bool is128BitLaneCrossingShuffleMask(MVT VT, ArrayRef<int> Mask) {
int LaneSize = 128 / VT.getScalarSizeInBits();
int Size = Mask.size();
for (int M : Mask.slice(0, Size / 2))
if (M >= 0 && (M % Size) >= Size / 2)
return true;
for (int M : Mask.slice(Size / 2, Size / 2))
if (M >= 0 && (M % Size) < Size / 2)
for (int i = 0; i < Size; ++i)
if (Mask[i] >= 0 && (Mask[i] % Size) / LaneSize != i / LaneSize)
return true;
return false;
}
@ -9200,7 +9203,7 @@ static SDValue lowerV4F64VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
// shuffles aren't a problem and FP and int have the same patterns.
// FIXME: We can handle these more cleverly than splitting for v4f64.
if (isHalfCrossingShuffleMask(Mask))
if (is128BitLaneCrossingShuffleMask(MVT::v4f64, Mask))
return splitAndLower256BitVectorShuffle(Op, V1, V2, Subtarget, DAG);
if (isSingleInputShuffleMask(Mask)) {
@ -9281,7 +9284,7 @@ static SDValue lowerV4I64VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
// FIXME: If we have AVX2, we should delegate to generic code as crossing
// shuffles aren't a problem and FP and int have the same patterns.
if (isHalfCrossingShuffleMask(Mask))
if (is128BitLaneCrossingShuffleMask(MVT::v4i64, Mask))
return splitAndLower256BitVectorShuffle(Op, V1, V2, Subtarget, DAG);
// AVX1 doesn't provide any facilities for v4i64 shuffles, bitcast and
@ -9306,7 +9309,7 @@ static SDValue lowerV8F32VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
ArrayRef<int> Mask = SVOp->getMask();
assert(Mask.size() == 8 && "Unexpected mask size for v8 shuffle!");
if (isHalfCrossingShuffleMask(Mask) ||
if (is128BitLaneCrossingShuffleMask(MVT::v8f32, Mask) ||
isSingleInputShuffleMask(Mask))
return splitAndLower256BitVectorShuffle(Op, V1, V2, Subtarget, DAG);