teach the optimizer how to constant fold uadd/usub intrinsics.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83295 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index d624deb..16f2c4d 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -677,6 +677,8 @@
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
+ case Intrinsic::uadd_with_overflow:
+ case Intrinsic::usub_with_overflow:
return true;
default:
return false;
@@ -756,7 +758,7 @@
if (!F->hasName()) return 0;
LLVMContext &Context = F->getContext();
StringRef Name = F->getName();
-
+
const Type *Ty = F->getReturnType();
if (NumOperands == 1) {
if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
@@ -881,6 +883,32 @@
}
return 0;
}
+
+
+ if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
+ if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
+ switch (F->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::uadd_with_overflow: {
+ Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
+ Constant *Ops[] = {
+ Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
+ };
+ return ConstantStruct::get(F->getContext(), Ops, 2, false);
+ }
+ case Intrinsic::usub_with_overflow: {
+ Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
+ Constant *Ops[] = {
+ Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
+ };
+ return ConstantStruct::get(F->getContext(), Ops, 2, false);
+ }
+ }
+ }
+
+ return 0;
+ }
+ return 0;
}
return 0;
}