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[X86] Move canLowerByDroppingEvenElements earlier to be with matchShuffleWithPACK. NFCI. 

Make sure its defined earlier so more shuffle lowering methods can use it.
This commit is contained in:
Simon Pilgrim 2020-03-30 15:41:28 +01:00
parent 464b9aeafe
commit 7a4a98a9c4
1 changed files with 66 additions and 66 deletions
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132
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -11229,6 +11229,72 @@ static SDValue lowerShuffleWithVPMOV(const SDLoc &DL, ArrayRef<int> Mask,
return DAG.getNode(X86ISD::VTRUNC, DL, VT, Src);
}
/// Check whether a compaction lowering can be done by dropping even
/// elements and compute how many times even elements must be dropped.
///
/// This handles shuffles which take every Nth element where N is a power of
/// two. Example shuffle masks:
///
/// N = 1: 0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14
/// N = 1: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30
/// N = 2: 0, 4, 8, 12, 0, 4, 8, 12, 0, 4, 8, 12, 0, 4, 8, 12
/// N = 2: 0, 4, 8, 12, 16, 20, 24, 28, 0, 4, 8, 12, 16, 20, 24, 28
/// N = 3: 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8
/// N = 3: 0, 8, 16, 24, 0, 8, 16, 24, 0, 8, 16, 24, 0, 8, 16, 24
///
/// Any of these lanes can of course be undef.
///
/// This routine only supports N <= 3.
/// FIXME: Evaluate whether either AVX or AVX-512 have any opportunities here
/// for larger N.
///
/// \returns N above, or the number of times even elements must be dropped if
/// there is such a number. Otherwise returns zero.
static int canLowerByDroppingEvenElements(ArrayRef<int> Mask,
bool IsSingleInput) {
// The modulus for the shuffle vector entries is based on whether this is
// a single input or not.
int ShuffleModulus = Mask.size() * (IsSingleInput ? 1 : 2);
assert(isPowerOf2_32((uint32_t)ShuffleModulus) &&
"We should only be called with masks with a power-of-2 size!");
uint64_t ModMask = (uint64_t)ShuffleModulus - 1;
// We track whether the input is viable for all power-of-2 strides 2^1, 2^2,
// and 2^3 simultaneously. This is because we may have ambiguity with
// partially undef inputs.
bool ViableForN[3] = {true, true, true};
for (int i = 0, e = Mask.size(); i < e; ++i) {
// Ignore undef lanes, we'll optimistically collapse them to the pattern we
// want.
if (Mask[i] < 0)
continue;
bool IsAnyViable = false;
for (unsigned j = 0; j != array_lengthof(ViableForN); ++j)
if (ViableForN[j]) {
uint64_t N = j + 1;
// The shuffle mask must be equal to (i * 2^N) % M.
if ((uint64_t)Mask[i] == (((uint64_t)i << N) & ModMask))
IsAnyViable = true;
else
ViableForN[j] = false;
}
// Early exit if we exhaust the possible powers of two.
if (!IsAnyViable)
break;
}
for (unsigned j = 0; j != array_lengthof(ViableForN); ++j)
if (ViableForN[j])
return j + 1;
// Return 0 as there is no viable power of two.
return 0;
}
// X86 has dedicated pack instructions that can handle specific truncation
// operations: PACKSS and PACKUS.
static bool matchShuffleWithPACK(MVT VT, MVT &SrcVT, SDValue &V1, SDValue &V2,
@ -14586,72 +14652,6 @@ static SDValue lowerV8I16Shuffle(const SDLoc &DL, ArrayRef<int> Mask,
Mask, Subtarget, DAG);
}
/// Check whether a compaction lowering can be done by dropping even
/// elements and compute how many times even elements must be dropped.
///
/// This handles shuffles which take every Nth element where N is a power of
/// two. Example shuffle masks:
///
/// N = 1: 0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14
/// N = 1: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30
/// N = 2: 0, 4, 8, 12, 0, 4, 8, 12, 0, 4, 8, 12, 0, 4, 8, 12
/// N = 2: 0, 4, 8, 12, 16, 20, 24, 28, 0, 4, 8, 12, 16, 20, 24, 28
/// N = 3: 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8, 0, 8
/// N = 3: 0, 8, 16, 24, 0, 8, 16, 24, 0, 8, 16, 24, 0, 8, 16, 24
///
/// Any of these lanes can of course be undef.
///
/// This routine only supports N <= 3.
/// FIXME: Evaluate whether either AVX or AVX-512 have any opportunities here
/// for larger N.
///
/// \returns N above, or the number of times even elements must be dropped if
/// there is such a number. Otherwise returns zero.
static int canLowerByDroppingEvenElements(ArrayRef<int> Mask,
bool IsSingleInput) {
// The modulus for the shuffle vector entries is based on whether this is
// a single input or not.
int ShuffleModulus = Mask.size() * (IsSingleInput ? 1 : 2);
assert(isPowerOf2_32((uint32_t)ShuffleModulus) &&
"We should only be called with masks with a power-of-2 size!");
uint64_t ModMask = (uint64_t)ShuffleModulus - 1;
// We track whether the input is viable for all power-of-2 strides 2^1, 2^2,
// and 2^3 simultaneously. This is because we may have ambiguity with
// partially undef inputs.
bool ViableForN[3] = {true, true, true};
for (int i = 0, e = Mask.size(); i < e; ++i) {
// Ignore undef lanes, we'll optimistically collapse them to the pattern we
// want.
if (Mask[i] < 0)
continue;
bool IsAnyViable = false;
for (unsigned j = 0; j != array_lengthof(ViableForN); ++j)
if (ViableForN[j]) {
uint64_t N = j + 1;
// The shuffle mask must be equal to (i * 2^N) % M.
if ((uint64_t)Mask[i] == (((uint64_t)i << N) & ModMask))
IsAnyViable = true;
else
ViableForN[j] = false;
}
// Early exit if we exhaust the possible powers of two.
if (!IsAnyViable)
break;
}
for (unsigned j = 0; j != array_lengthof(ViableForN); ++j)
if (ViableForN[j])
return j + 1;
// Return 0 as there is no viable power of two.
return 0;
}
static SDValue lowerShuffleWithPERMV(const SDLoc &DL, MVT VT,
ArrayRef<int> Mask, SDValue V1,
SDValue V2, SelectionDAG &DAG) {