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[APInt] Remove calls to clearUnusedBits from XorSlowCase and operator^=

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Summary:
There's a comment in XorSlowCase that says "0^0==1" which isn't true. 0 xored with 0 is still 0. So I don't think we need to clear any unused bits here.

Now there is no difference between XorSlowCase and AndSlowCase/OrSlowCase other than the operation being performed

Reviewers: majnemer, MatzeB, chandlerc, bkramer

Reviewed By: MatzeB

Subscribers: chfast, llvm-commits

Differential Revision: https://reviews.llvm.org/D28986

llvm-svn: 292873
This commit is contained in:
Craig Topper 2017-01-24 02:10:15 +00:00
parent e929d35db5
commit dc69bac218
2 changed files with 32 additions and 6 deletions
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8
lib/Support/APInt.cpp
View File

@ -440,13 +440,12 @@ APInt& APInt::operator^=(const APInt& RHS) {
assert(BitWidth == RHS.BitWidth && "Bit widths must be the same");
if (isSingleWord()) {
VAL ^= RHS.VAL;
this->clearUnusedBits();
return *this;
}
unsigned numWords = getNumWords();
for (unsigned i = 0; i < numWords; ++i)
pVal[i] ^= RHS.pVal[i];
return clearUnusedBits();
return *this;
}
APInt APInt::AndSlowCase(const APInt& RHS) const {
@ -471,10 +470,7 @@ APInt APInt::XorSlowCase(const APInt& RHS) const {
for (unsigned i = 0; i < numWords; ++i)
val[i] = pVal[i] ^ RHS.pVal[i];
APInt Result(val, getBitWidth());
// 0^0==1 so clear the high bits in case they got set.
Result.clearUnusedBits();
return Result;
return APInt(val, getBitWidth());
}
APInt APInt::operator*(const APInt& RHS) const {

30
unittests/ADT/APIntTest.cpp
View File

@ -158,6 +158,36 @@ TEST(APIntTest, i1) {
EXPECT_EQ(two, one - neg_one);
EXPECT_EQ(zero, one - one);
// And
EXPECT_EQ(zero, zero & zero);
EXPECT_EQ(zero, one & zero);
EXPECT_EQ(zero, zero & one);
EXPECT_EQ(one, one & one);
EXPECT_EQ(zero, zero & zero);
EXPECT_EQ(zero, neg_one & zero);
EXPECT_EQ(zero, zero & neg_one);
EXPECT_EQ(neg_one, neg_one & neg_one);
// Or
EXPECT_EQ(zero, zero | zero);
EXPECT_EQ(one, one | zero);
EXPECT_EQ(one, zero | one);
EXPECT_EQ(one, one | one);
EXPECT_EQ(zero, zero | zero);
EXPECT_EQ(neg_one, neg_one | zero);
EXPECT_EQ(neg_one, zero | neg_one);
EXPECT_EQ(neg_one, neg_one | neg_one);
// Xor
EXPECT_EQ(zero, zero ^ zero);
EXPECT_EQ(one, one ^ zero);
EXPECT_EQ(one, zero ^ one);
EXPECT_EQ(zero, one ^ one);
EXPECT_EQ(zero, zero ^ zero);
EXPECT_EQ(neg_one, neg_one ^ zero);
EXPECT_EQ(neg_one, zero ^ neg_one);
EXPECT_EQ(zero, neg_one ^ neg_one);
// Shifts.
EXPECT_EQ(zero, one << one);
EXPECT_EQ(one, one << zero);