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[APInt] Add APInt::setBits() method to set all bits in range

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The current pattern for setting bits in range is typically:

Mask |= APInt::getBitsSet(MaskSizeInBits, LoPos, HiPos);

Which can be particularly slow for large APInts (MaskSizeInBits > 64) as they require the allocation memory for the temporary variable.

This is one of the key compile time issues identified in PR32037.

This patch adds the APInt::setBits() helper method which avoids the temporary memory allocation completely, this first implementation uses setBit() internally instead but already significantly reduces the regression in PR32037 (~10% drop). Additional optimization may be possible.

I investigated whether there is need for APInt::clearBits() and APInt::flipBits() equivalents but haven't seen these patterns to be particularly common, but reusing the code would be trivial.

Differential Revision: https://reviews.llvm.org/D30265

llvm-svn: 296102
This commit is contained in:
Simon Pilgrim 2017-02-24 10:15:29 +00:00
parent 135a02ddbf
commit af689eb896
5 changed files with 136 additions and 9 deletions
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3
include/llvm/ADT/APInt.h
View File

@ -1239,6 +1239,9 @@ public:
/// Set the given bit to 1 whose position is given as "bitPosition".
void setBit(unsigned bitPosition);
/// Set the bits from loBit (inclusive) to hiBit (exclusive) to 1.
void setBits(unsigned loBit, unsigned hiBit);
/// \brief Set every bit to 0.
void clearAllBits() {
if (isSingleWord())

33
lib/Support/APInt.cpp
View File

@ -565,6 +565,39 @@ void APInt::setBit(unsigned bitPosition) {
pVal[whichWord(bitPosition)] |= maskBit(bitPosition);
}
void APInt::setBits(unsigned loBit, unsigned hiBit) {
assert(hiBit <= BitWidth && "hiBit out of range");
assert(loBit <= hiBit && loBit <= BitWidth && "loBit out of range");
if (loBit == hiBit)
return;
if (isSingleWord())
*this |= APInt::getBitsSet(BitWidth, loBit, hiBit);
else {
unsigned hiBit1 = hiBit - 1;
unsigned loWord = whichWord(loBit);
unsigned hiWord = whichWord(hiBit1);
if (loWord == hiWord) {
// Set bits are all within the same word, create a [loBit,hiBit) mask.
uint64_t mask = UINT64_MAX;
mask >>= (APINT_BITS_PER_WORD - (hiBit - loBit));
mask <<= whichBit(loBit);
pVal[loWord] |= mask;
} else {
// Set bits span multiple words, create a lo mask with set bits starting
// at loBit, a hi mask with set bits below hiBit and set all bits of the
// words in between.
uint64_t loMask = UINT64_MAX << whichBit(loBit);
uint64_t hiMask = UINT64_MAX >> (64 - whichBit(hiBit1) - 1);
pVal[loWord] |= loMask;
pVal[hiWord] |= hiMask;
for (unsigned word = loWord + 1; word < hiWord; ++word)
pVal[word] = UINT64_MAX;
}
}
}
/// Set the given bit to 0 whose position is given as "bitPosition".
/// @brief Set a given bit to 0.
void APInt::clearBit(unsigned bitPosition) {

12
lib/Target/X86/X86ISelLowering.cpp
View File

@ -5236,8 +5236,7 @@ static bool getTargetConstantBitsFromNode(SDValue Op, unsigned EltSizeInBits,
return false;
unsigned CstSizeInBits = Cst->getType()->getPrimitiveSizeInBits();
if (isa<UndefValue>(Cst)) {
unsigned HiBits = BitOffset + CstSizeInBits;
Undefs |= APInt::getBitsSet(SizeInBits, BitOffset, HiBits);
Undefs.setBits(BitOffset, BitOffset + CstSizeInBits);
return true;
}
if (auto *CInt = dyn_cast<ConstantInt>(Cst)) {
@ -5258,8 +5257,7 @@ static bool getTargetConstantBitsFromNode(SDValue Op, unsigned EltSizeInBits,
const SDValue &Src = Op.getOperand(i);
unsigned BitOffset = i * SrcEltSizeInBits;
if (Src.isUndef()) {
unsigned HiBits = BitOffset + SrcEltSizeInBits;
UndefBits |= APInt::getBitsSet(SizeInBits, BitOffset, HiBits);
UndefBits.setBits(BitOffset, BitOffset + SrcEltSizeInBits);
continue;
}
auto *Cst = cast<ConstantSDNode>(Src);
@ -26353,11 +26351,11 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
break;
LLVM_FALLTHROUGH;
case X86ISD::SETCC:
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - 1);
KnownZero.setBits(1, BitWidth);
break;
case X86ISD::MOVMSK: {
unsigned NumLoBits = Op.getOperand(0).getValueType().getVectorNumElements();
KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - NumLoBits);
KnownZero.setBits(NumLoBits, BitWidth);
break;
}
case X86ISD::VZEXT: {
@ -26374,7 +26372,7 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
DAG.computeKnownBits(N0, KnownZero, KnownOne, DemandedSrcElts, Depth + 1);
KnownOne = KnownOne.zext(BitWidth);
KnownZero = KnownZero.zext(BitWidth);
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - InBitWidth);
KnownZero.setBits(InBitWidth, BitWidth);
break;
}
}

3
lib/Target/X86/X86ShuffleDecodeConstantPool.cpp
View File

@ -60,8 +60,7 @@ static bool extractConstantMask(const Constant *C, unsigned MaskEltSizeInBits,
unsigned BitOffset = i * CstEltSizeInBits;
if (isa<UndefValue>(COp)) {
unsigned HiBits = BitOffset + CstEltSizeInBits;
UndefBits |= APInt::getBitsSet(CstSizeInBits, BitOffset, HiBits);
UndefBits.setBits(BitOffset, BitOffset + CstEltSizeInBits);
continue;
}

94
unittests/ADT/APIntTest.cpp
View File

@ -63,6 +63,26 @@ TEST(APIntTest, i33_Count) {
EXPECT_EQ(((uint64_t)-2)&((1ull<<33) -1), i33minus2.getZExtValue());
}
TEST(APIntTest, i61_Count) {
APInt i61(61, 1 << 15);
EXPECT_EQ(45u, i61.countLeadingZeros());
EXPECT_EQ(0u, i61.countLeadingOnes());
EXPECT_EQ(16u, i61.getActiveBits());
EXPECT_EQ(15u, i61.countTrailingZeros());
EXPECT_EQ(1u, i61.countPopulation());
EXPECT_EQ((1 << 15), i61.getSExtValue());
EXPECT_EQ((1 << 15), i61.getZExtValue());
i61.setBits(8, 19);
EXPECT_EQ(42u, i61.countLeadingZeros());
EXPECT_EQ(0u, i61.countLeadingOnes());
EXPECT_EQ(19u, i61.getActiveBits());
EXPECT_EQ(8u, i61.countTrailingZeros());
EXPECT_EQ(11u, i61.countPopulation());
EXPECT_EQ((1 << 19) - (1 << 8), i61.getSExtValue());
EXPECT_EQ((1 << 19) - (1 << 8), i61.getZExtValue());
}
TEST(APIntTest, i65_Count) {
APInt i65(65, 0, true);
EXPECT_EQ(65u, i65.countLeadingZeros());
@ -118,6 +138,80 @@ TEST(APIntTest, i128_PositiveCount) {
EXPECT_EQ(1u, one.countPopulation());
EXPECT_EQ(1, one.getSExtValue());
EXPECT_EQ(1u, one.getZExtValue());
APInt s128(128, 2, true);
EXPECT_EQ(126u, s128.countLeadingZeros());
EXPECT_EQ(0u, s128.countLeadingOnes());
EXPECT_EQ(2u, s128.getActiveBits());
EXPECT_EQ(1u, s128.countTrailingZeros());
EXPECT_EQ(0u, s128.countTrailingOnes());
EXPECT_EQ(1u, s128.countPopulation());
EXPECT_EQ(2, s128.getSExtValue());
EXPECT_EQ(2u, s128.getZExtValue());
// NOP Test
s128.setBits(42, 42);
EXPECT_EQ(126u, s128.countLeadingZeros());
EXPECT_EQ(0u, s128.countLeadingOnes());
EXPECT_EQ(2u, s128.getActiveBits());
EXPECT_EQ(1u, s128.countTrailingZeros());
EXPECT_EQ(0u, s128.countTrailingOnes());
EXPECT_EQ(1u, s128.countPopulation());
EXPECT_EQ(2, s128.getSExtValue());
EXPECT_EQ(2u, s128.getZExtValue());
s128.setBits(3, 32);
EXPECT_EQ(96u, s128.countLeadingZeros());
EXPECT_EQ(0u, s128.countLeadingOnes());
EXPECT_EQ(32u, s128.getActiveBits());
EXPECT_EQ(33u, s128.getMinSignedBits());
EXPECT_EQ(1u, s128.countTrailingZeros());
EXPECT_EQ(0u, s128.countTrailingOnes());
EXPECT_EQ(30u, s128.countPopulation());
EXPECT_EQ(static_cast<uint32_t>((~0u << 3) | 2), s128.getZExtValue());
s128.setBits(62, 128);
EXPECT_EQ(0u, s128.countLeadingZeros());
EXPECT_EQ(66u, s128.countLeadingOnes());
EXPECT_EQ(128u, s128.getActiveBits());
EXPECT_EQ(63u, s128.getMinSignedBits());
EXPECT_EQ(1u, s128.countTrailingZeros());
EXPECT_EQ(0u, s128.countTrailingOnes());
EXPECT_EQ(96u, s128.countPopulation());
EXPECT_EQ(static_cast<int64_t>((3ull << 62) |
static_cast<uint32_t>((~0u << 3) | 2)),
s128.getSExtValue());
}
TEST(APIntTest, i256) {
APInt s256(256, 15, true);
EXPECT_EQ(252u, s256.countLeadingZeros());
EXPECT_EQ(0u, s256.countLeadingOnes());
EXPECT_EQ(4u, s256.getActiveBits());
EXPECT_EQ(0u, s256.countTrailingZeros());
EXPECT_EQ(4u, s256.countTrailingOnes());
EXPECT_EQ(4u, s256.countPopulation());
EXPECT_EQ(15, s256.getSExtValue());
EXPECT_EQ(15u, s256.getZExtValue());
s256.setBits(62, 66);
EXPECT_EQ(190u, s256.countLeadingZeros());
EXPECT_EQ(0u, s256.countLeadingOnes());
EXPECT_EQ(66u, s256.getActiveBits());
EXPECT_EQ(67u, s256.getMinSignedBits());
EXPECT_EQ(0u, s256.countTrailingZeros());
EXPECT_EQ(4u, s256.countTrailingOnes());
EXPECT_EQ(8u, s256.countPopulation());
s256.setBits(60, 256);
EXPECT_EQ(0u, s256.countLeadingZeros());
EXPECT_EQ(196u, s256.countLeadingOnes());
EXPECT_EQ(256u, s256.getActiveBits());
EXPECT_EQ(61u, s256.getMinSignedBits());
EXPECT_EQ(0u, s256.countTrailingZeros());
EXPECT_EQ(4u, s256.countTrailingOnes());
EXPECT_EQ(200u, s256.countPopulation());
EXPECT_EQ(static_cast<int64_t>((~0ull << 60) | 15), s256.getSExtValue());
}
TEST(APIntTest, i1) {