[X86][clang] Put the update of HasLongDouble into TargetInfo::adjust

[pengfei]

Summary

We found a problem that -mlong-double-64 doesn't work with -mno-x87
due to the flag HasLongDouble was set earlier that the option taking
effect. https://godbolt.org/z/9hn8MnPr6

This patch fixes the problem by moving the update of HasLongDouble into
TargetInfo::adjust so that we can update it correctly.

[erichkeane]

@craig.topper is the only one I know who can keep all of this straight, so perhaps he's willing to give a more in depth review?

clang/include/clang/Basic/TargetInfo.h

207

This seems so shockingly x86 specific, I'm a little concerned we are doing it here.

clang/include/clang/Basic/TargetInfo.h

protected:
   bool NoAsmVariants;  // True if {|} are normal characters.
   bool HasLegalHalfType; // True if the backend supports operations on the half
                          // LLVM IR type.
   bool HasFloat128;
   bool HasFloat16;
   bool HasBFloat16;
   bool HasIbm128;
   bool HasLongDouble;
+  bool Has80BitLongDouble;
   bool HasFPReturn;
   bool HasStrictFP;
 
   unsigned char MaxAtomicPromoteWidth, MaxAtomicInlineWidth;
   unsigned short SimdDefaultAlign;
   std::string DataLayoutString;
   const char *UserLabelPrefix;
   const char *MCountName;

clang/lib/Basic/TargetInfo.cpp

TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   VLASupported = true;
   NoAsmVariants = false;
   HasLegalHalfType = false;
   HasFloat128 = false;
   HasIbm128 = false;
   HasFloat16 = false;
   HasBFloat16 = false;
   HasLongDouble = true;
+  Has80BitLongDouble = false;
   HasFPReturn = true;
   HasStrictFP = false;
   PointerWidth = PointerAlign = 32;
   BoolWidth = BoolAlign = 8;
   IntWidth = IntAlign = 32;
   LongWidth = LongAlign = 32;
   LongLongWidth = LongLongAlign = 64;
 
if (Opts.LongDoubleSize == DoubleWidth) {
       LongDoubleAlign = DoubleAlign;
       LongDoubleFormat = DoubleFormat;
     } else if (Opts.LongDoubleSize == 128) {
       LongDoubleWidth = LongDoubleAlign = 128;
       LongDoubleFormat = &llvm::APFloat::IEEEquad();
     }
   }
 
+  if (LongDoubleFormat == &llvm::APFloat::x87DoubleExtended())
+    HasLongDouble = Has80BitLongDouble;
+
   if (Opts.NewAlignOverride)
     NewAlign = Opts.NewAlignOverride * getCharWidth();
 
   // Each unsigned fixed point type has the same number of fractional bits as
   // its corresponding signed type.
   PaddingOnUnsignedFixedPoint |= Opts.PaddingOnUnsignedFixedPoint;
   CheckFixedPointBits();
 

clang/lib/Basic/Targets/X86.cpp

if ((FPMath == FP_SSE && SSELevel < SSE1) ||
     return false;
   }
 
   SimdDefaultAlign =
       hasFeature("avx512f") ? 512 : hasFeature("avx") ? 256 : 128;
 
   // FIXME: We should allow long double type on 32-bits to match with GCC.
   // This requires backend to be able to lower f80 without x87 first.
-  if (!HasX87 && LongDoubleFormat == &llvm::APFloat::x87DoubleExtended())
-    HasLongDouble = false;
+  if (HasX87)
+    Has80BitLongDouble = true;
 
   if (SSELevel < SSE1 && getTriple().getArch() == llvm::Triple::x86_64)
     HasFPReturn = false;
 
   return true;
 }
 
 /// X86TargetInfo::getTargetDefines - Return the set of the X86-specific macro

clang/test/Sema/x86-no-x87.cpp

 // RUN: %clang_cc1 -fsyntax-only -verify %s -triple i686-linux-gnu -target-feature -x87
 // RUN: %clang_cc1 -fsyntax-only -verify %s -triple i686-linux-gnu -DNOERROR
+// RUN: %clang_cc1 -fsyntax-only -verify %s -triple i686-linux-gnu -mlong-double-64 -DNOERROR
 
 #ifdef NOERROR
 // expected-no-diagnostics
 #endif
 
 typedef long double long_double;
 
 // Declaration is fine, unless it is called or defined.

clang/test/Sema/x86_64-no-x87.cpp

 // RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-linux-gnu -target-feature -x87 -target-feature -sse -DERROR_LONGDOUBLE -DERROR_NOSSE
 // RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-linux-gnu -target-feature -x87 -DERROR_LONGDOUBLE
 // RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-linux-gnu -DNOERROR
+// RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-linux-gnu -mlong-double-64 -DNOERROR
 
 #ifdef NOERROR
 // expected-no-diagnostics
 #endif
 
 typedef long double long_double;
 
 // Declaration is fine, unless it is called or defined.