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| author | Reid Spencer <rspencer@reidspencer.com> | 2007-03-25 21:58:42 +0000 |
|---|---|---|
| committer | Reid Spencer <rspencer@reidspencer.com> | 2007-03-25 21:58:42 +0000 |
| commit | f6bef488eeab75b6c7746f9faa9731d45bb84aef (patch) | |
| tree | 9e6ed6c2f6d7e3ceef7d1b0dac49353cdf2908b0 | |
| parent | 9031aca96bf83379f837e1e590dc19dd67a3fdcd (diff) | |
Compute getLowBitsSet correctly. Using the complement of a 64-bit value
and shifting down without regard for the bitwidth of the APInt can lead
to incorrect initialization values. Instead, check for the word size case
(to avoid undef results from shift) and then do (1 << loBitsSet) - 1
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35344 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | include/llvm/ADT/APInt.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/include/llvm/ADT/APInt.h b/include/llvm/ADT/APInt.h index b39cf78b98..25ea4a2bd5 100644 --- a/include/llvm/ADT/APInt.h +++ b/include/llvm/ADT/APInt.h @@ -374,11 +374,12 @@ public: // Handle a degenerate case, to avoid shifting by word size if (loBitsSet == 0) return APInt(numBits, 0); - uint32_t shiftAmt = numBits - loBitsSet; + if (loBitsSet == APINT_BITS_PER_WORD) + return APInt(numBits, -1ULL); // For small values, return quickly - if (numBits <= APINT_BITS_PER_WORD) - return APInt(numBits, ~0ULL >> shiftAmt); - return (~APInt(numBits, 0)).lshr(shiftAmt); + if (numBits < APINT_BITS_PER_WORD) + return APInt(numBits, (1ULL << loBitsSet) - 1); + return (~APInt(numBits, 0)).lshr(numBits - loBitsSet); } /// The hash value is computed as the sum of the words and the bit width. |