+bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
+ LVILatticeVal &Result, bool isTrueDest) {
+ if (ICI && isa<Constant>(ICI->getOperand(1))) {
+ if (ICI->isEquality() && ICI->getOperand(0) == Val) {
+ // We know that V has the RHS constant if this is a true SETEQ or
+ // false SETNE.
+ if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
+ Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
+ else
+ Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
+ return true;
+ }
+
+ // Recognize the range checking idiom that InstCombine produces.
+ // (X-C1) u< C2 --> [C1, C1+C2)
+ ConstantInt *NegOffset = nullptr;
+ if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
+ match(ICI->getOperand(0), m_Add(m_Specific(Val),
+ m_ConstantInt(NegOffset)));
+
+ ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
+ if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
+ // Calculate the range of values that would satisfy the comparison.
+ ConstantRange CmpRange(CI->getValue());
+ ConstantRange TrueValues =
+ ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
+
+ if (NegOffset) // Apply the offset from above.
+ TrueValues = TrueValues.subtract(NegOffset->getValue());
+
+ // If we're interested in the false dest, invert the condition.
+ if (!isTrueDest) TrueValues = TrueValues.inverse();
+
+ Result = LVILatticeVal::getRange(TrueValues);
+ return true;
+ }
+ }
+
+ return false;
+}
+