[llvm] r296272 - [APInt] Add APInt::extractBits() method to extract APInt subrange (reapplied)
Simon Pilgrim via llvm-commits
llvm-commits at lists.llvm.org
Sat Feb 25 12:01:58 PST 2017
Author: rksimon
Date: Sat Feb 25 14:01:58 2017
New Revision: 296272
URL: http://llvm.org/viewvc/llvm-project?rev=296272&view=rev
Log:
[APInt] Add APInt::extractBits() method to extract APInt subrange (reapplied)
The current pattern for extract bits in range is typically:
Mask.lshr(BitOffset).trunc(SubSizeInBits);
Which can be particularly slow for large APInts (MaskSizeInBits > 64) as they require the allocation of memory for the temporary variable.
This is another of the compile time issues identified in PR32037 (see also D30265).
This patch adds the APInt::extractBits() helper method which avoids the temporary memory allocation.
Differential Revision: https://reviews.llvm.org/D30336
Modified:
llvm/trunk/include/llvm/ADT/APInt.h
llvm/trunk/lib/Support/APInt.cpp
llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp
llvm/trunk/unittests/ADT/APIntTest.cpp
Modified: llvm/trunk/include/llvm/ADT/APInt.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=296272&r1=296271&r2=296272&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/APInt.h (original)
+++ llvm/trunk/include/llvm/ADT/APInt.h Sat Feb 25 14:01:58 2017
@@ -1272,6 +1272,9 @@ public:
/// as "bitPosition".
void flipBit(unsigned bitPosition);
+ /// Return an APInt with the extracted bits [bitPosition,bitPosition+numBits).
+ APInt extractBits(unsigned numBits, unsigned bitPosition) const;
+
/// @}
/// \name Value Characterization Functions
/// @{
Modified: llvm/trunk/lib/Support/APInt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=296272&r1=296271&r2=296272&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APInt.cpp (original)
+++ llvm/trunk/lib/Support/APInt.cpp Sat Feb 25 14:01:58 2017
@@ -618,6 +618,42 @@ void APInt::flipBit(unsigned bitPosition
else setBit(bitPosition);
}
+APInt APInt::extractBits(unsigned numBits, unsigned bitPosition) const {
+ assert(numBits > 0 && "Can't extract zero bits");
+ assert(bitPosition < BitWidth && (numBits + bitPosition) <= BitWidth &&
+ "Illegal bit extraction");
+
+ if (isSingleWord())
+ return APInt(numBits, VAL >> bitPosition);
+
+ unsigned loBit = whichBit(bitPosition);
+ unsigned loWord = whichWord(bitPosition);
+ unsigned hiWord = whichWord(bitPosition + numBits - 1);
+
+ // Single word result extracting bits from a single word source.
+ if (loWord == hiWord)
+ return APInt(numBits, pVal[loWord] >> loBit);
+
+ // Extracting bits that start on a source word boundary can be done
+ // as a fast memory copy.
+ if (loBit == 0)
+ return APInt(numBits, makeArrayRef(pVal + loWord, 1 + hiWord - loWord));
+
+ // General case - shift + copy source words directly into place.
+ APInt Result(numBits, 0);
+ unsigned NumSrcWords = getNumWords();
+ unsigned NumDstWords = Result.getNumWords();
+
+ for (unsigned word = 0; word < NumDstWords; ++word) {
+ uint64_t w0 = pVal[loWord + word];
+ uint64_t w1 =
+ (loWord + word + 1) < NumSrcWords ? pVal[loWord + word + 1] : 0;
+ Result.pVal[word] = (w0 >> loBit) | (w1 << (APINT_BITS_PER_WORD - loBit));
+ }
+
+ return Result.clearUnusedBits();
+}
+
unsigned APInt::getBitsNeeded(StringRef str, uint8_t radix) {
assert(!str.empty() && "Invalid string length");
assert((radix == 10 || radix == 8 || radix == 16 || radix == 2 ||
Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=296272&r1=296271&r2=296272&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Sat Feb 25 14:01:58 2017
@@ -5207,8 +5207,8 @@ static bool getTargetConstantBitsFromNod
EltBits.resize(NumElts, APInt(EltSizeInBits, 0));
for (unsigned i = 0; i != NumElts; ++i) {
- APInt UndefEltBits = UndefBits.lshr(i * EltSizeInBits);
- UndefEltBits = UndefEltBits.zextOrTrunc(EltSizeInBits);
+ unsigned BitOffset = i * EltSizeInBits;
+ APInt UndefEltBits = UndefBits.extractBits(EltSizeInBits, BitOffset);
// Only treat an element as UNDEF if all bits are UNDEF.
if (UndefEltBits.isAllOnesValue()) {
@@ -5223,7 +5223,7 @@ static bool getTargetConstantBitsFromNod
if (UndefEltBits.getBoolValue() && !AllowPartialUndefs)
return false;
- APInt Bits = MaskBits.lshr(i * EltSizeInBits).zextOrTrunc(EltSizeInBits);
+ APInt Bits = MaskBits.extractBits(EltSizeInBits, BitOffset);
EltBits[i] = Bits.getZExtValue();
}
return true;
@@ -6421,7 +6421,7 @@ static Constant *getConstantVector(MVT V
SmallVector<Constant *, 32> ConstantVec;
for (unsigned i = 0; i < NumElm; i++) {
- APInt Val = SplatValue.lshr(ScalarSize * i).trunc(ScalarSize);
+ APInt Val = SplatValue.extractBits(ScalarSize, ScalarSize * i);
Constant *Const;
if (VT.isFloatingPoint()) {
assert((ScalarSize == 32 || ScalarSize == 64) &&
Modified: llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp?rev=296272&r1=296271&r2=296272&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp Sat Feb 25 14:01:58 2017
@@ -77,8 +77,8 @@ static bool extractConstantMask(const Co
RawMask.resize(NumMaskElts, 0);
for (unsigned i = 0; i != NumMaskElts; ++i) {
- APInt EltUndef = UndefBits.lshr(i * MaskEltSizeInBits);
- EltUndef = EltUndef.zextOrTrunc(MaskEltSizeInBits);
+ unsigned BitOffset = i * MaskEltSizeInBits;
+ APInt EltUndef = UndefBits.extractBits(MaskEltSizeInBits, BitOffset);
// Only treat the element as UNDEF if all bits are UNDEF, otherwise
// treat it as zero.
@@ -88,8 +88,7 @@ static bool extractConstantMask(const Co
continue;
}
- APInt EltBits = MaskBits.lshr(i * MaskEltSizeInBits);
- EltBits = EltBits.zextOrTrunc(MaskEltSizeInBits);
+ APInt EltBits = MaskBits.extractBits(MaskEltSizeInBits, BitOffset);
RawMask[i] = EltBits.getZExtValue();
}
Modified: llvm/trunk/unittests/ADT/APIntTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/APIntTest.cpp?rev=296272&r1=296271&r2=296272&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/APIntTest.cpp (original)
+++ llvm/trunk/unittests/ADT/APIntTest.cpp Sat Feb 25 14:01:58 2017
@@ -1505,3 +1505,19 @@ TEST(APIntTest, reverseBits) {
}
}
}
+
+TEST(APIntTest, extractBits) {
+ APInt i32(32, 0x1234567);
+ EXPECT_EQ(0x3456, i32.extractBits(16, 4));
+
+ APInt i257(257, 0xFFFFFFFFFF0000FFull, true);
+ EXPECT_EQ(0xFFu, i257.extractBits(16, 0));
+ EXPECT_EQ((0xFFu >> 1), i257.extractBits(16, 1));
+ EXPECT_EQ(-1, i257.extractBits(32, 64).getSExtValue());
+ EXPECT_EQ(-1, i257.extractBits(128, 128).getSExtValue());
+ EXPECT_EQ(-1, i257.extractBits(66, 191).getSExtValue());
+ EXPECT_EQ(static_cast<int64_t>(0xFFFFFFFFFF80007Full),
+ i257.extractBits(128, 1).getSExtValue());
+ EXPECT_EQ(static_cast<int64_t>(0xFFFFFFFFFF80007Full),
+ i257.extractBits(129, 1).getSExtValue());
+}
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