diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp index 8a0d91dfe51..33af7ee0eff 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp @@ -733,7 +733,22 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { // TODO: eventually we should lower this intrinsic to IR if (auto CIWidth = dyn_cast<ConstantInt>(II->getArgOperand(2))) { if (auto CIStart = dyn_cast<ConstantInt>(II->getArgOperand(3))) { - if (CIWidth->equalsInt(64) && CIStart->isZero()) { + unsigned Index = CIStart->getZExtValue(); + // From AMD documentation: "a value of zero in the field length is + // defined as length of 64". + unsigned Length = CIWidth->equalsInt(0) ? 64 : CIWidth->getZExtValue(); + + // From AMD documentation: "If the sum of the bit index + length field + // is greater than 64, the results are undefined". + + // Note that both field index and field length are 8-bit quantities. + // Since variables 'Index' and 'Length' are unsigned values + // obtained from zero-extending field index and field length + // respectively, their sum should never wrap around. + if ((Index + Length) > 64) + return ReplaceInstUsesWith(CI, UndefValue::get(II->getType())); + + if (Length == 64 && Index == 0) { Value *Vec = II->getArgOperand(1); Value *Undef = UndefValue::get(Vec->getType()); const uint32_t Mask[] = { 0, 2 }; |
