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[APInt] Fix extractBits to correctly handle Result.isSingleWord() case.

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Summary: extractBits assumes that `!this->isSingleWord() implies !Result.isSingleWord()`, which may not necessarily be true. Handle both cases.

Reviewers: RKSimon

Subscribers: sanjoy, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D43363

llvm-svn: 325311
This commit is contained in:
Tim Shen 2018-02-16 01:44:36 +00:00
parent c35b1c26b0
commit adad8e65a1
2 changed files with 9 additions and 1 deletions
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3
lib/Support/APInt.cpp
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@ -428,11 +428,12 @@ APInt APInt::extractBits(unsigned numBits, unsigned bitPosition) const {
unsigned NumSrcWords = getNumWords();
unsigned NumDstWords = Result.getNumWords();
uint64_t *DestPtr = Result.isSingleWord() ? &Result.U.VAL : Result.U.pVal;
for (unsigned word = 0; word < NumDstWords; ++word) {
uint64_t w0 = U.pVal[loWord + word];
uint64_t w1 =
(loWord + word + 1) < NumSrcWords ? U.pVal[loWord + word + 1] : 0;
Result.U.pVal[word] = (w0 >> loBit) | (w1 << (APINT_BITS_PER_WORD - loBit));
DestPtr[word] = (w0 >> loBit) | (w1 << (APINT_BITS_PER_WORD - loBit));
}
return Result.clearUnusedBits();

7
unittests/ADT/APIntTest.cpp
View File

@ -1768,6 +1768,13 @@ TEST(APIntTest, extractBits) {
i257.extractBits(128, 1).getSExtValue());
EXPECT_EQ(static_cast<int64_t>(0xFFFFFFFFFF80007Full),
i257.extractBits(129, 1).getSExtValue());
EXPECT_EQ(APInt(48, 0),
APInt(144, "281474976710655", 10).extractBits(48, 48));
EXPECT_EQ(APInt(48, 0x0000ffffffffffffull),
APInt(144, "281474976710655", 10).extractBits(48, 0));
EXPECT_EQ(APInt(48, 0x00007fffffffffffull),
APInt(144, "281474976710655", 10).extractBits(48, 1));
}
TEST(APIntTest, getLowBitsSet) {