[clang][Interp] Implement __builtin_isfinite

[aaron.ballman]

clang/lib/AST/Interp/InterpBuiltin.cpp

195

We have platforms on which the width of an integer is not 32-bits; because this is pushing values back onto the stack, won't we run into some odd issues where builtin + 1 would be adding a 32-bit and a 16-bit value?

[tbaeder]

clang/lib/AST/Interp/InterpBuiltin.cpp

195

Yes, you don't even need to add anything for it to fail. I can add a way of doing that in a follow-up commit. And/or add an assertion now.

Also, what platform would that be? So I can add a test later.

[aaron.ballman]

LGTM

clang/lib/AST/Interp/InterpBuiltin.cpp

195

AVR and MSP430 both use 16-bit int, I don't know of anyone using 8-bit currently. You can search for IntWidth = to see the choices made by various targets (default is 32-bit though).

clang/lib/AST/Interp/InterpBuiltin.cpp

static bool interp__builtin_isinf(InterpState &S, CodePtr OpPC,
   if (CheckSign)
     S.Stk.push<Integral<32, true>>(
         Integral<32, true>::from(IsInf ? (Arg.isNegative() ? -1 : 1) : 0));
   else
     S.Stk.push<Integral<32, true>>(Integral<32, true>::from(Arg.isInf()));
   return true;
 }
 
+static bool interp__builtin_isfinite(InterpState &S, CodePtr OpPC,
+                                     const InterpFrame *Frame,
+                                     const Function *F) {
+  const Floating &Arg = S.Stk.peek<Floating>();
+
+  S.Stk.push<Integral<32, true>>(Integral<32, true>::from(Arg.isFinite()));
+  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);
if (interp__builtin_isinf(S, OpPC, Frame, F, /*Sign=*/false))
       return Ret<PT_Sint32>(S, OpPC, Dummy);
     break;
 
   case Builtin::BI__builtin_isinf_sign:
     if (interp__builtin_isinf(S, OpPC, Frame, F, /*Sign=*/true))
       return Ret<PT_Sint32>(S, OpPC, Dummy);
     break;
 
+  case Builtin::BI__builtin_isfinite:
+    if (interp__builtin_isfinite(S, OpPC, Frame, F))
+      return Ret<PT_Sint32>(S, OpPC, Dummy);
+    break;
+
   default:
     return false;
   }
 
   return false;
 }
 
 } // namespace interp
 } // namespace clang

clang/test/AST/Interp/builtin-functions.cpp

namespace fmin {
   static_assert(min2 == 1, "");
   constexpr float min3 = __builtin_fmin(__builtin_inf(), __builtin_nan(""));
   static_assert(min3 == __builtin_inf(), "");
 }
 
 namespace inf {
   static_assert(__builtin_isinf(__builtin_inf()), "");
   static_assert(!__builtin_isinf(1.0), "");
+
+  static_assert(__builtin_isfinite(1.0), "");
+  static_assert(!__builtin_isfinite(__builtin_inf()), "");
 }