[Target] Use IEEE quad format for long double on Fuchsia x86_64

[phosek]

Summary

This change unifies the long double format between x86_64 and aarch64
targets making it easier to write code that's independent of the target.

[mcgrathr]

clang/lib/Basic/Targets/X86.h

858

Can we just do this in FuchsiaTargetInfo generically?
I think we'd like to make our core API types uniform across machines and this makes sure that we get the Fuchsia common choice rather than a machine-specific choice that might differ in a new machine.

clang/lib/Basic/Targets.cpp

case llvm::Triple::DragonFly:
       return new DragonFlyBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::NetBSD:
       return new NetBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::OpenBSD:
       return new OpenBSDX86_64TargetInfo(Triple, Opts);
     case llvm::Triple::FreeBSD:
       return new FreeBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::Fuchsia:
-      return new FuchsiaTargetInfo<X86_64TargetInfo>(Triple, Opts);
+      return new FuchsiaX86_64TargetInfo(Triple, Opts);
     case llvm::Triple::KFreeBSD:
       return new KFreeBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::Solaris:
       return new SolarisTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::Win32: {
       switch (Triple.getEnvironment()) {
       case llvm::Triple::Cygnus:
         return new CygwinX86_64TargetInfo(Triple, Opts);

clang/lib/Basic/Targets/X86.h

 public:
   AndroidX86_64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
       : LinuxTargetInfo<X86_64TargetInfo>(Triple, Opts) {
     LongDoubleFormat = &llvm::APFloat::IEEEquad();
   }
 
   const char *getLongDoubleMangling() const override { return "g"; }
 };
+
+// x86_64 Fuchsia target
+class LLVM_LIBRARY_VISIBILITY FuchsiaX86_64TargetInfo
+    : public FuchsiaTargetInfo<X86_64TargetInfo> {
+public:
+  FuchsiaX86_64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
+      : FuchsiaTargetInfo<X86_64TargetInfo>(Triple, Opts) {
+    LongDoubleFormat = &llvm::APFloat::IEEEquad();
+  }
+};
+
 } // namespace targets
 } // namespace clang
+
 #endif // LLVM_CLANG_LIB_BASIC_TARGETS_X86_H