[Clang] Mutate long-double math builtins into f128 under IEEE-quad

Under -mabi=ieeelongdouble on PowerPC, IEEE-quad floating point semantic
is used for long double. This patch mutates call to related builtins
into f128 version on PowerPC. And in theory, this should be applied to
other targets when their backend supports IEEE 128-bit style libcalls.

GCC already has these mutations except nansl, which is not available on
PowerPC along with other variants (nans, nansf).

Reviewed By: RKSimon, nemanjai

Differential Revision: https://reviews.llvm.org/D92080

clang/lib/CodeGen/CGBuiltin.cpp

@@ -2107,6 +2107,78 @@ RValue CodeGenFunction::emitRotate(const CallExpr *E, bool IsRotateRight) {
   return RValue::get(Builder.CreateCall(F, { Src, Src, ShiftAmt }));
 }
 
+// Map math builtins for long-double to f128 version.
+static unsigned mutateLongDoubleBuiltin(unsigned BuiltinID) {
+  switch (BuiltinID) {
+#define MUTATE_LDBL(func) \
+  case Builtin::BI__builtin_##func##l: \
+    return Builtin::BI__builtin_##func##f128;
+  MUTATE_LDBL(sqrt)
+  MUTATE_LDBL(cbrt)
+  MUTATE_LDBL(fabs)
+  MUTATE_LDBL(log)
+  MUTATE_LDBL(log2)
+  MUTATE_LDBL(log10)
+  MUTATE_LDBL(log1p)
+  MUTATE_LDBL(logb)
+  MUTATE_LDBL(exp)
+  MUTATE_LDBL(exp2)
+  MUTATE_LDBL(expm1)
+  MUTATE_LDBL(fdim)
+  MUTATE_LDBL(hypot)
+  MUTATE_LDBL(ilogb)
+  MUTATE_LDBL(pow)
+  MUTATE_LDBL(fmin)
+  MUTATE_LDBL(fmax)
+  MUTATE_LDBL(ceil)
+  MUTATE_LDBL(trunc)
+  MUTATE_LDBL(rint)
+  MUTATE_LDBL(nearbyint)
+  MUTATE_LDBL(round)
+  MUTATE_LDBL(floor)
+  MUTATE_LDBL(lround)
+  MUTATE_LDBL(llround)
+  MUTATE_LDBL(lrint)
+  MUTATE_LDBL(llrint)
+  MUTATE_LDBL(fmod)
+  MUTATE_LDBL(modf)
+  MUTATE_LDBL(nan)
+  MUTATE_LDBL(nans)
+  MUTATE_LDBL(inf)
+  MUTATE_LDBL(fma)
+  MUTATE_LDBL(sin)
+  MUTATE_LDBL(cos)
+  MUTATE_LDBL(tan)
+  MUTATE_LDBL(sinh)
+  MUTATE_LDBL(cosh)
+  MUTATE_LDBL(tanh)
+  MUTATE_LDBL(asin)
+  MUTATE_LDBL(acos)
+  MUTATE_LDBL(atan)
+  MUTATE_LDBL(asinh)
+  MUTATE_LDBL(acosh)
+  MUTATE_LDBL(atanh)
+  MUTATE_LDBL(atan2)
+  MUTATE_LDBL(erf)
+  MUTATE_LDBL(erfc)
+  MUTATE_LDBL(ldexp)
+  MUTATE_LDBL(frexp)
+  MUTATE_LDBL(huge_val)
+  MUTATE_LDBL(copysign)
+  MUTATE_LDBL(nextafter)
+  MUTATE_LDBL(nexttoward)
+  MUTATE_LDBL(remainder)
+  MUTATE_LDBL(remquo)
+  MUTATE_LDBL(scalbln)
+  MUTATE_LDBL(scalbn)
+  MUTATE_LDBL(tgamma)
+  MUTATE_LDBL(lgamma)
+#undef MUTATE_LDBL
+  default:
+    return BuiltinID;
+  }
+}
+
 RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                                         const CallExpr *E,
                                         ReturnValueSlot ReturnValue) {
@@ -2123,6 +2195,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                                                Result.Val.getFloat()));
   }
 
+  // If current long-double semantics is IEEE 128-bit, replace math builtins
+  // of long-double with f128 equivalent.
+  // TODO: This mutation should also be applied to other targets other than PPC,
+  // after backend supports IEEE 128-bit style libcalls.
+  if (getTarget().getTriple().isPPC64() &&
+      &getTarget().getLongDoubleFormat() == &llvm::APFloat::IEEEquad())
+    BuiltinID = mutateLongDoubleBuiltin(BuiltinID);
+
   // If the builtin has been declared explicitly with an assembler label,
   // disable the specialized emitting below. Ideally we should communicate the
   // rename in IR, or at least avoid generating the intrinsic calls that are