Fixed by masking off the upper bits that we are shifting off before
doing the left shift.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249689
91177308-0d34-0410-b5e6-
96231b3b80d8
// Mask off any existing bits in the upper part of the lower value that
// we want to replace.
val[0] &= (1 << startBit) - 1;
// Mask off any existing bits in the upper part of the lower value that
// we want to replace.
val[0] &= (1 << startBit) - 1;
- // Now shift in the new bits
- val[0] |= value << startBit;
+ unsigned numBitsFirstVal = (sizeof(value_type) * 8) - startBit;
+ unsigned lowerVal = value;
+ if (startBit > 0) {
+ // Mask off the upper bits in the new value that are not going to go into
+ // the lower value. This avoids a left shift of a negative value, which
+ // is undefined behavior.
+ lowerVal &= ((1 << numBitsFirstVal) - 1);
+ // Now shift the new bits into place
+ lowerVal <<= startBit;
+ }
+ val[0] |= lowerVal;
// Mask off any existing bits in the lower part of the upper value that
// we want to replace.
val[1] &= ~((1 << startBit) - 1);
// Next shift the bits that go into the upper value into position.
// Mask off any existing bits in the lower part of the upper value that
// we want to replace.
val[1] &= ~((1 << startBit) - 1);
// Next shift the bits that go into the upper value into position.
- unsigned numBitsFirstVal = (sizeof(value_type) * 8) - startBit;
unsigned upperVal = value >> numBitsFirstVal;
// Mask off upper bits after right shift in case of signed type.
upperVal &= (1 << startBit) - 1;
unsigned upperVal = value >> numBitsFirstVal;
// Mask off upper bits after right shift in case of signed type.
upperVal &= (1 << startBit) - 1;