i64 -1, whose sign bit is the 0th one, can't be left shifted without invoking UB.
https://reviews.llvm.org/D23362
llvm-svn: 278280
if (isSingleWord()) {
if (shiftAmt == BitWidth)
return APInt(BitWidth, 0); // undefined
- else {
- unsigned SignBit = APINT_BITS_PER_WORD - BitWidth;
- return APInt(BitWidth,
- (((int64_t(VAL) << SignBit) >> SignBit) >> shiftAmt));
- }
+ return APInt(BitWidth, SignExtend64(VAL, BitWidth) >> shiftAmt);
}
// If all the bits were shifted out, the result is, technically, undefined.
EXPECT_FALSE(Shl[1]);
}
+TEST(APIntTest, i64_ArithmeticRightShiftNegative) {
+ const APInt neg_one(64, static_cast<uint64_t>(-1), true);
+ EXPECT_EQ(neg_one, neg_one.ashr(7));
+}
+
TEST(APIntTest, i128_NegativeCount) {
APInt Minus3(128, static_cast<uint64_t>(-3), true);
EXPECT_EQ(126u, Minus3.countLeadingOnes());