Extend ConstantFolding to understand signed overflow variants
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83338 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 1ca7cb0..0ce1c24 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -678,6 +678,8 @@
case Intrinsic::cttz:
case Intrinsic::uadd_with_overflow:
case Intrinsic::usub_with_overflow:
+ case Intrinsic::sadd_with_overflow:
+ case Intrinsic::ssub_with_overflow:
return true;
default:
return false;
@@ -902,6 +904,28 @@
};
return ConstantStruct::get(F->getContext(), Ops, 2, false);
}
+ case Intrinsic::sadd_with_overflow: {
+ Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
+ Constant *Overflow = ConstantExpr::getSelect(
+ ConstantExpr::getICmp(CmpInst::ICMP_SGT,
+ ConstantInt::get(Op1->getType(), 0), Op1),
+ ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
+ ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
+
+ Constant *Ops[] = { Res, Overflow };
+ return ConstantStruct::get(F->getContext(), Ops, 2, false);
+ }
+ case Intrinsic::ssub_with_overflow: {
+ Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
+ Constant *Overflow = ConstantExpr::getSelect(
+ ConstantExpr::getICmp(CmpInst::ICMP_SGT,
+ ConstantInt::get(Op2->getType(), 0), Op2),
+ ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
+ ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
+
+ Constant *Ops[] = { Res, Overflow };
+ return ConstantStruct::get(F->getContext(), Ops, 2, false);
+ }
}
}