[clang][Interp] Implement __builtin_inf() etc.

[tbaeder]

Tests will come in a later commit.

[cor3ntin]

clang/lib/AST/Interp/InterpBuiltin.cpp

119

why does that return a bool? you could make it void, and get rid of the if statement

[tbaeder]

clang/lib/AST/Interp/InterpBuiltin.cpp

119

No reason other than that all the evaluation functions (also in Interp.h) return bool, even if they always succeed.

[cor3ntin]

clang/lib/AST/Interp/InterpBuiltin.cpp

119

Yeah, I'm not a fan of returning something for no reason but i buy the consistency argument

clang/lib/AST/Interp/InterpBuiltin.cpp

else
       Result = Floating(
           llvm::APFloat::getSNaN(TargetSemantics, /*Negative=*/false, &Fill));
   }
 
   S.Stk.push<Floating>(Result);
   return true;
 }
 
+static bool interp__builtin_inf(InterpState &S, CodePtr OpPC,
+                                const InterpFrame *Frame, const Function *F) {
+  const llvm::fltSemantics &TargetSemantics =
+      S.getCtx().getFloatTypeSemantics(F->getDecl()->getReturnType());
+
+  S.Stk.push<Floating>(Floating::getInf(TargetSemantics));
+  return true;
+}
+
 bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F) {
   InterpFrame *Frame = S.Current;
   APValue Dummy;
 
   switch (F->getBuiltinID()) {
   case Builtin::BI__builtin_is_constant_evaluated:
     S.Stk.push<Boolean>(Boolean::from(S.inConstantContext()));
     return Ret<PT_Bool>(S, OpPC, Dummy);
bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F) {
   case Builtin::BI__builtin_nans:
   case Builtin::BI__builtin_nansf:
   case Builtin::BI__builtin_nansl:
   case Builtin::BI__builtin_nansf16:
   case Builtin::BI__builtin_nansf128:
     if (interp__builtin_nan(S, OpPC, Frame, F, /*Signaling=*/true))
       return Ret<PT_Float>(S, OpPC, Dummy);
     break;
+  case Builtin::BI__builtin_inf:
+  case Builtin::BI__builtin_inff:
+  case Builtin::BI__builtin_infl:
+  case Builtin::BI__builtin_inff16:
+  case Builtin::BI__builtin_inff128:
+    if (interp__builtin_inf(S, OpPC, Frame, F))
+      return Ret<PT_Float>(S, OpPC, Dummy);
+    break;
 
   default:
     return false;
   }
 
   return false;
 }
 
 } // namespace interp
 } // namespace clang