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Fix APInt::operator*= so that it computes the correct result for large integers where there is unsigned overflow. Fix APFloat::toString so that it doesn't depend on the incorrect behavior in common cases (and computes the correct result in some rare cases). Fixes PR11086.

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llvm-svn: 141441
This commit is contained in:
Eli Friedman 2011-10-07 23:40:49 +00:00
parent 8b0cf65af7
commit 433785c651
3 changed files with 12 additions and 2 deletions
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2
lib/Support/APFloat.cpp
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@ -3455,7 +3455,7 @@ void APFloat::toString(SmallVectorImpl<char> &Str,
// <= semantics->precision + e * 137 / 59
// (log_2(5) ~ 2.321928 < 2.322034 ~ 137/59)
unsigned precision = semantics->precision + 137 * texp / 59;
unsigned precision = semantics->precision + (137 * texp + 136) / 59;
// Multiply significand by 5^e.
// N * 5^0101 == N * 5^(1*1) * 5^(0*2) * 5^(1*4) * 5^(0*8)

3
lib/Support/APInt.cpp
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@ -386,6 +386,7 @@ APInt& APInt::operator*=(const APInt& RHS) {
clearAllBits();
unsigned wordsToCopy = destWords >= getNumWords() ? getNumWords() : destWords;
memcpy(pVal, dest, wordsToCopy * APINT_WORD_SIZE);
clearUnusedBits();
// delete dest array and return
delete[] dest;
@ -471,7 +472,7 @@ APInt APInt::operator*(const APInt& RHS) const {
return APInt(BitWidth, VAL * RHS.VAL);
APInt Result(*this);
Result *= RHS;
return Result.clearUnusedBits();
return Result;
}
APInt APInt::operator+(const APInt& RHS) const {

9
unittests/ADT/APIntTest.cpp
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@ -441,4 +441,13 @@ TEST(APIntTest, StringDeath) {
#endif
#endif
TEST(APIntTest, mul_clear) {
APInt ValA(65, -1ULL);
APInt ValB(65, 4);
APInt ValC(65, 0);
ValC = ValA * ValB;
ValA *= ValB;
EXPECT_EQ(ValA.toString(10, false), ValC.toString(10, false));
}
}