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Don't invoke undefined behavior in shifts in the functions getHighBitsSet

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and getLowBitsSet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35311 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Spencer 2007-03-24 23:35:54 +00:00
parent 8f969ee62c
commit ca76fc2cd3
1 changed files with 6 additions and 6 deletions
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12
include/llvm/ADT/APInt.h
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@ -357,12 +357,11 @@ public:
/// @brief Get a value with high bits set
static APInt getHighBitsSet(uint32_t numBits, uint32_t hiBitsSet) {
assert(hiBitsSet <= numBits && "Too many bits to set!");
uint32_t mvBits = numBits - hiBitsSet;
uint32_t shiftAmt = numBits - hiBitsSet;
// For small values, return quickly
if (numBits <= APINT_BITS_PER_WORD)
return APInt(numBits, ((1ULL << hiBitsSet) - 1) << mvBits);
APInt Result(numBits, 1);
return (APInt(numBits, 1).shl(hiBitsSet) - APInt(numBits, 1)).shl(mvBits);
return APInt(numBits, ~0ULL << shiftAmt);
return (~APInt(numBits, 0)).shl(shiftAmt);
}
/// Constructs an APInt value that has the bottom loBitsSet bits set.
@ -371,10 +370,11 @@ public:
/// @brief Get a value with low bits set
static APInt getLowBitsSet(uint32_t numBits, uint32_t loBitsSet) {
assert(loBitsSet <= numBits && "Too many bits to set!");
uint32_t shiftAmt = numBits - loBitsSet;
// For small values, return quickly
if (numBits <= APINT_BITS_PER_WORD)
return APInt(numBits, (1ULL << loBitsSet) - 1ULL);
return APInt(numBits, 1).shl(loBitsSet) - APInt(numBits, 1);
return APInt(numBits, ~0ULL >> shiftAmt);
return (~APInt(numBits, 0)).lshr(shiftAmt);
}
/// The hash value is computed as the sum of the words and the bit width.