From ca76fc2cd3b97e4821e7d8247bc03bbbd2789ad9 Mon Sep 17 00:00:00 2001 From: Reid Spencer Date: Sat, 24 Mar 2007 23:35:54 +0000 Subject: [PATCH] Don't invoke undefined behavior in shifts in the functions getHighBitsSet and getLowBitsSet. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35311 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/ADT/APInt.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/include/llvm/ADT/APInt.h b/include/llvm/ADT/APInt.h index 4ceef2df3ca..fb6246d0084 100644 --- a/include/llvm/ADT/APInt.h +++ b/include/llvm/ADT/APInt.h @@ -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.