+ // ext(and(opnd, cst)) --> and(ext(opnd), ext(cst))
+ if ((Inst->getOpcode() == Instruction::And ||
+ Inst->getOpcode() == Instruction::Or))
+ return true;
+
+ // ext(xor(opnd, cst)) --> xor(ext(opnd), ext(cst))
+ if (Inst->getOpcode() == Instruction::Xor) {
+ const ConstantInt *Cst = dyn_cast<ConstantInt>(Inst->getOperand(1));
+ // Make sure it is not a NOT.
+ if (Cst && !Cst->getValue().isAllOnesValue())
+ return true;
+ }
+
+ // zext(shrl(opnd, cst)) --> shrl(zext(opnd), zext(cst))
+ // It may change a poisoned value into a regular value, like
+ // zext i32 (shrl i8 %val, 12) --> shrl i32 (zext i8 %val), 12
+ // poisoned value regular value
+ // It should be OK since undef covers valid value.
+ if (Inst->getOpcode() == Instruction::LShr && !IsSExt)
+ return true;
+
+ // and(ext(shl(opnd, cst)), cst) --> and(shl(ext(opnd), ext(cst)), cst)
+ // It may change a poisoned value into a regular value, like
+ // zext i32 (shl i8 %val, 12) --> shl i32 (zext i8 %val), 12
+ // poisoned value regular value
+ // It should be OK since undef covers valid value.
+ if (Inst->getOpcode() == Instruction::Shl && Inst->hasOneUse()) {
+ const Instruction *ExtInst =
+ dyn_cast<const Instruction>(*Inst->user_begin());
+ if (ExtInst->hasOneUse()) {
+ const Instruction *AndInst =
+ dyn_cast<const Instruction>(*ExtInst->user_begin());
+ if (AndInst && AndInst->getOpcode() == Instruction::And) {
+ const ConstantInt *Cst = dyn_cast<ConstantInt>(AndInst->getOperand(1));
+ if (Cst &&
+ Cst->getValue().isIntN(Inst->getType()->getIntegerBitWidth()))
+ return true;
+ }
+ }
+ }
+