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add uadd_ov/usub_ov to apint, consolidate constant folding 

logic to use the new APInt methods.  Among other things this
implements rdar://8501501 - llvm.smul.with.overflow.i32 should constant fold

which comes from "clang -ftrapv", originally brought to my attention from PR8221.

llvm-svn: 116457
This commit is contained in:
Chris Lattner 2010-10-14 00:05:07 +00:00
parent edf5e640fa
commit 698661c741
4 changed files with 54 additions and 35 deletions
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6
llvm/include/llvm/ADT/APInt.h
View File

@ -806,10 +806,10 @@ public:
// Operations that return overflow indicators.
// ssub_ov - Signed subtraction. Unsigned subtraction never overflows.
APInt sadd_ov(const APInt &RHS, bool &Overflow) const;
APInt uadd_ov(const APInt &RHS, bool &Overflow) const;
APInt ssub_ov(const APInt &RHS, bool &Overflow) const;
APInt usub_ov(const APInt &RHS, bool &Overflow) const;
APInt sdiv_ov(const APInt &RHS, bool &Overflow) const;
APInt smul_ov(const APInt &RHS, bool &Overflow) const;
APInt sshl_ov(unsigned Amt, bool &Overflow) const;
@ -877,7 +877,7 @@ public:
/// the validity of the less-than relationship.
/// @returns true if *this < RHS when both are considered unsigned.
/// @brief Unsigned less than comparison
bool ult(const APInt& RHS) const;
bool ult(const APInt &RHS) const;
/// Regards both *this as an unsigned quantity and compares it with RHS for
/// the validity of the less-than relationship.

60
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -1001,6 +1001,7 @@ llvm::canConstantFoldCallTo(const Function *F) {
case Intrinsic::usub_with_overflow:
case Intrinsic::sadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::convert_from_fp16:
case Intrinsic::convert_to_fp16:
return true;
@ -1248,42 +1249,37 @@ llvm::ConstantFoldCall(Function *F,
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.
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::smul_with_overflow: {
APInt Res;
bool Overflow;
switch (F->getIntrinsicID()) {
default: assert(0 && "Invalid case");
case Intrinsic::sadd_with_overflow:
Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::uadd_with_overflow:
Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::ssub_with_overflow:
Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::usub_with_overflow:
Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::smul_with_overflow:
Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow);
break;
}
Constant *Ops[] = {
Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
ConstantInt::get(F->getContext(), Res),
ConstantInt::get(Type::getInt1Ty(F->getContext()), 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);
}
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);
}
}
}

12
llvm/lib/Support/APInt.cpp
View File

@ -2053,6 +2053,12 @@ APInt APInt::sadd_ov(const APInt &RHS, bool &Overflow) const {
return Res;
}
APInt APInt::uadd_ov(const APInt &RHS, bool &Overflow) const {
APInt Res = *this+RHS;
Overflow = Res.ult(RHS);
return Res;
}
APInt APInt::ssub_ov(const APInt &RHS, bool &Overflow) const {
APInt Res = *this - RHS;
Overflow = isNonNegative() != RHS.isNonNegative() &&
@ -2060,6 +2066,12 @@ APInt APInt::ssub_ov(const APInt &RHS, bool &Overflow) const {
return Res;
}
APInt APInt::usub_ov(const APInt &RHS, bool &Overflow) const {
APInt Res = *this+RHS;
Overflow = Res.ugt(RHS);
return Res;
}
APInt APInt::sdiv_ov(const APInt &RHS, bool &Overflow) const {
// MININT/-1 --> overflow.
Overflow = isMinSignedValue() && RHS.isAllOnesValue();

11
llvm/test/Transforms/ConstProp/overflow-ops.ll
View File

@ -170,3 +170,14 @@ declare {i8, i1} @llvm.usub.with.overflow.i8(i8, i8)
declare {i8, i1} @llvm.sadd.with.overflow.i8(i8, i8)
declare {i8, i1} @llvm.ssub.with.overflow.i8(i8, i8)
declare {i8, i1} @llvm.smul.with.overflow.i8(i8, i8)
; rdar://8501501
define {i8, i1} @smul_1() nounwind {
entry:
%t = call {i8, i1} @llvm.smul.with.overflow.i8(i8 -20, i8 -10)
ret {i8, i1} %t
; CHECK: @smul_1
; CHECK: ret %i8i1 { i8 -56, i1 true }
}