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Fix the > 64 bits case for left shift.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34564 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Spencer 2007-02-25 00:56:44 +00:00
parent 99c49a4b94
commit 8755380fff
1 changed files with 47 additions and 22 deletions
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69
lib/Support/APInt.cpp
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@ -946,34 +946,59 @@ APInt APInt::lshr(uint32_t shiftAmt) const {
/// @brief Left-shift function. /// @brief Left-shift function.
APInt APInt::shl(uint32_t shiftAmt) const { APInt APInt::shl(uint32_t shiftAmt) const {
assert(shiftAmt <= BitWidth && "Invalid shift amount"); assert(shiftAmt <= BitWidth && "Invalid shift amount");
APInt API(*this); if (isSingleWord()) {
if (API.isSingleWord()) {
if (shiftAmt == BitWidth) if (shiftAmt == BitWidth)
API.VAL = 0; return APInt(BitWidth, 0); // avoid undefined shift results
else return APInt(BitWidth, (VAL << shiftAmt) &
API.VAL <<= shiftAmt; (~uint64_t(0ULL) >>
API.clearUnusedBits(); (APINT_BITS_PER_WORD - BitWidth)));
return API;
} }
if (shiftAmt == BitWidth) { // If all the bits were shifted out, the result is 0. This avoids issues
memset(API.pVal, 0, getNumWords() * APINT_WORD_SIZE); // with shifting by the size of the integer type, which produces undefined
return API; // results. We define these "undefined results" to always be 0.
if (shiftAmt == BitWidth)
return APInt(BitWidth, 0);
// Create some space for the result.
uint64_t * val = new uint64_t[getNumWords()];
// If we are shifting less than a word, do it the easy way
if (shiftAmt < APINT_BITS_PER_WORD) {
uint64_t carry = 0;
shiftAmt %= APINT_BITS_PER_WORD;
for (uint32_t i = 0; i < getNumWords(); i++) {
val[i] = pVal[i] << shiftAmt | carry;
carry = pVal[i] >> (APINT_BITS_PER_WORD - shiftAmt);
}
val[getNumWords()-1] &= ~uint64_t(0ULL) >> (APINT_BITS_PER_WORD - BitWidth);
return APInt(val, BitWidth);
} }
if (uint32_t offset = shiftAmt / APINT_BITS_PER_WORD) { // Compute some values needed by the remaining shift algorithms
for (uint32_t i = API.getNumWords() - 1; i > offset - 1; --i) uint32_t wordShift = shiftAmt % APINT_BITS_PER_WORD;
API.pVal[i] = API.pVal[i-offset]; uint32_t offset = shiftAmt / APINT_BITS_PER_WORD;
memset(API.pVal, 0, offset * APINT_WORD_SIZE);
// If we are shifting whole words, just move whole words
if (wordShift == 0) {
for (uint32_t i = 0; i < offset; i++)
val[i] = 0;
for (uint32_t i = offset; i < getNumWords(); i++)
val[i] = pVal[i-offset];
val[getNumWords()-1] &= ~uint64_t(0ULL) >> (APINT_BITS_PER_WORD - BitWidth);
return APInt(val,BitWidth);
} }
shiftAmt %= APINT_BITS_PER_WORD;
uint32_t i; // Copy whole words from this to Result.
for (i = API.getNumWords() - 1; i > 0; --i) uint32_t i = getNumWords() - 1;
API.pVal[i] = (API.pVal[i] << shiftAmt) | for (; i > offset; --i)
(API.pVal[i-1] >> (APINT_BITS_PER_WORD - shiftAmt)); val[i] = pVal[i-offset] << wordShift |
API.pVal[i] <<= shiftAmt; pVal[i-offset-1] >> (APINT_BITS_PER_WORD - wordShift);
API.clearUnusedBits(); val[offset] = pVal[offset-1] << wordShift;
return API; for (i = 0; i < offset; ++i)
val[i] = 0;
val[getNumWords()-1] &= ~uint64_t(0ULL) >> (APINT_BITS_PER_WORD - BitWidth);
return APInt(val, BitWidth);
} }
/// Implementation of Knuth's Algorithm D (Division of nonnegative integers) /// Implementation of Knuth's Algorithm D (Division of nonnegative integers)