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[Clang] constexpr builtin floating point classification / comparison functions #94118

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Merged
merged 7 commits into from
Aug 18, 2024
Merged

[Clang] constexpr builtin floating point classification / comparison functions #94118

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ed1c00e
constexpr __builtin_signbit
MitalAshok Jun 1, 2024
f08f0c4
constexpr __builtin_is{less|greater|...|unordered}
MitalAshok Jun 1, 2024
0d9de42
Regenerate clang/test/Analysis/builtin_signbit.cpp
MitalAshok Jun 1, 2024
49e9468
Add release note
MitalAshok Jun 4, 2024
5f9f9c5
Merge remote-tracking branch 'origin' into constexpr-__builtin_signbit
MitalAshok Jun 4, 2024
afc4703
Simplifiy comparison function logic
MitalAshok Jun 4, 2024
2745785
Merge branch 'main' into constexpr-__builtin_signbit
MitalAshok Aug 18, 2024
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20 changes: 11 additions & 9 deletions clang/include/clang/Basic/Builtins.td
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Original file line number Diff line number Diff line change
Expand Up @@ -533,42 +533,42 @@ def BuiltinComplex : Builtin {
def IsGreater : Builtin {
let Spellings = ["__builtin_isgreater"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def IsGreaterEqual : Builtin {
let Spellings = ["__builtin_isgreaterequal"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def IsLess : Builtin {
let Spellings = ["__builtin_isless"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def IsLessEqual : Builtin {
let Spellings = ["__builtin_islessequal"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def IsLessGreater : Builtin {
let Spellings = ["__builtin_islessgreater"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def IsUnordered : Builtin {
let Spellings = ["__builtin_isunordered"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

Expand Down Expand Up @@ -646,19 +646,21 @@ def IsFPClass : Builtin {
def Signbit : Builtin {
let Spellings = ["__builtin_signbit"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
CustomTypeChecking];
CustomTypeChecking, Constexpr];
let Prototype = "int(...)";
}

def SignbitF : Builtin {
let Spellings = ["__builtin_signbitf"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
Constexpr];
let Prototype = "int(float)";
}

def SignbitL : Builtin {
let Spellings = ["__builtin_signbitl"];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const];
let Attributes = [FunctionWithBuiltinPrefix, NoThrow, Const,
Constexpr];
let Prototype = "int(long double)";
}

Expand Down
67 changes: 67 additions & 0 deletions clang/lib/AST/ExprConstant.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12650,6 +12650,73 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
Success(Val.isZero() ? 1 : 0, E);
}

case Builtin::BI__builtin_signbit:
case Builtin::BI__builtin_signbitf:
case Builtin::BI__builtin_signbitl: {
APFloat Val(0.0);
return EvaluateFloat(E->getArg(0), Val, Info) &&
Success(Val.isNegative() ? 1 : 0, E);
}

case Builtin::BI__builtin_isgreater:
case Builtin::BI__builtin_isgreaterequal:
case Builtin::BI__builtin_isless:
case Builtin::BI__builtin_islessequal:
case Builtin::BI__builtin_islessgreater:
case Builtin::BI__builtin_isunordered: {
APFloat LHS(0.0);
APFloat RHS(0.0);
if (!EvaluateFloat(E->getArg(0), LHS, Info) ||
!EvaluateFloat(E->getArg(1), RHS, Info))
return false;

APFloat::cmpResult Cmp = LHS.compare(RHS);
bool FunctionResult;
if (BuiltinOp == Builtin::BI__builtin_isunordered ||
Cmp == APFloat::cmpResult::cmpUnordered) {
FunctionResult = BuiltinOp == Builtin::BI__builtin_isunordered &&
Cmp == APFloat::cmpResult::cmpUnordered;
} else {
int CmpStrong;
switch (Cmp) {
case APFloat::cmpResult::cmpEqual:
CmpStrong = 0;
break;
case APFloat::cmpResult::cmpLessThan:
CmpStrong = -1;
break;
case APFloat::cmpResult::cmpGreaterThan:
CmpStrong = 1;
break;
default:
llvm_unreachable("Unchecked cmpResult enum");
}

switch (BuiltinOp) {
case Builtin::BI__builtin_isgreater:
FunctionResult = CmpStrong > 0;
break;
case Builtin::BI__builtin_isgreaterequal:
FunctionResult = CmpStrong >= 0;
break;
case Builtin::BI__builtin_isless:
FunctionResult = CmpStrong < 0;
break;
case Builtin::BI__builtin_islessequal:
FunctionResult = CmpStrong <= 0;
break;
case Builtin::BI__builtin_islessgreater:
FunctionResult = CmpStrong != 0;
break;
default:
llvm_unreachable("Unexpected builtin ID: Should be a floating point "
"comparison function");
}
}

return Success(FunctionResult ? 1 : 0, E);
}

case Builtin::BI__builtin_issignaling: {
APFloat Val(0.0);
return EvaluateFloat(E->getArg(0), Val, Info) &&
Expand Down
87 changes: 87 additions & 0 deletions clang/lib/AST/Interp/InterpBuiltin.cpp
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Expand Up @@ -430,6 +430,78 @@ static bool interp__builtin_iszero(InterpState &S, CodePtr OpPC,
return true;
}

static bool interp__builtin_signbit(InterpState &S, CodePtr OpPC,
const InterpFrame *Frame, const Function *F,
const CallExpr *Call) {
const Floating &Arg = S.Stk.peek<Floating>();

pushInteger(S, Arg.isNegative(), Call->getType());
return true;
}

static bool interp_floating_comparison(InterpState &S, CodePtr OpPC,
const InterpFrame *Frame,
const Function *F,
const CallExpr *Call) {
const Floating &RHS = S.Stk.peek<Floating>();
const Floating &LHS = S.Stk.peek<Floating>(align(2u * primSize(PT_Float)));
unsigned ID = F->getBuiltinID();
assert(ID == Builtin::BI__builtin_isgreater ||
ID == Builtin::BI__builtin_isgreaterequal ||
ID == Builtin::BI__builtin_isless ||
ID == Builtin::BI__builtin_islessequal ||
ID == Builtin::BI__builtin_islessgreater ||
ID == Builtin::BI__builtin_isunordered);

ComparisonCategoryResult Cmp = LHS.compare(RHS);
bool FunctionResult;
if (ID == Builtin::BI__builtin_isunordered ||
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It would be nice if we could share much of this implementation with the one in ExprConstant.cpp instead of duplicating the code. However, I don't insist (eventually I hope the ExprConstant.cpp code will go away).

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It turned out much nicer when I switched on the builtin ID first, so there's not much left to share. This could be extracted to a bool ComparisonFunction(unsigned BuiltinID, const APFloat &LHS, const APFloat &RHS), but I don't know where I could put that so that ExprConstant.cpp and InterpBuiltin.cpp could both access it

Cmp == ComparisonCategoryResult::Unordered) {
FunctionResult = ID == Builtin::BI__builtin_isunordered &&
Cmp == ComparisonCategoryResult::Unordered;
} else {
int CmpStrong;
switch (Cmp) {
case ComparisonCategoryResult::Equal:
case ComparisonCategoryResult::Equivalent:
CmpStrong = 0;
break;
case ComparisonCategoryResult::Less:
CmpStrong = -1;
break;
case ComparisonCategoryResult::Greater:
CmpStrong = 1;
break;
default:
llvm_unreachable("Unchecked ComparisonCategoryResult enum");
}

switch (ID) {
case Builtin::BI__builtin_isgreater:
FunctionResult = CmpStrong > 0;
break;
case Builtin::BI__builtin_isgreaterequal:
FunctionResult = CmpStrong >= 0;
break;
case Builtin::BI__builtin_isless:
FunctionResult = CmpStrong < 0;
break;
case Builtin::BI__builtin_islessequal:
FunctionResult = CmpStrong <= 0;
break;
case Builtin::BI__builtin_islessgreater:
FunctionResult = CmpStrong != 0;
break;
default:
llvm_unreachable("Unexpected builtin ID: Should be a floating point "
"comparison function");
}
}

pushInteger(S, FunctionResult, Call->getType());
return true;
}

/// First parameter to __builtin_isfpclass is the floating value, the
/// second one is an integral value.
static bool interp__builtin_isfpclass(InterpState &S, CodePtr OpPC,
Expand Down Expand Up @@ -1214,6 +1286,21 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
if (!interp__builtin_iszero(S, OpPC, Frame, F, Call))
return false;
break;
case Builtin::BI__builtin_signbit:
case Builtin::BI__builtin_signbitf:
case Builtin::BI__builtin_signbitl:
if (!interp__builtin_signbit(S, OpPC, Frame, F, Call))
return false;
break;
case Builtin::BI__builtin_isgreater:
case Builtin::BI__builtin_isgreaterequal:
case Builtin::BI__builtin_isless:
case Builtin::BI__builtin_islessequal:
case Builtin::BI__builtin_islessgreater:
case Builtin::BI__builtin_isunordered:
if (!interp_floating_comparison(S, OpPC, Frame, F, Call))
return false;
break;
case Builtin::BI__builtin_isfpclass:
if (!interp__builtin_isfpclass(S, OpPC, Frame, F, Call))
return false;
Expand Down
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