Fix the calling convention of Mingw64 long double values

GCC uses the x87DoubleExtended model for long doubles, and passes them
indirectly by address through function calls.

Also replace the existing mingw-long-double assembly emitting test with
an IR-level test.

llvm-svn: 251567

1 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 0094ce8cc5c..a0c379aeb7f 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -4009,7 +4009,13 @@ public:
 class MinGWX86_64TargetInfo : public WindowsX86_64TargetInfo {
 public:
   MinGWX86_64TargetInfo(const llvm::Triple &Triple)
-      : WindowsX86_64TargetInfo(Triple) {}
+      : WindowsX86_64TargetInfo(Triple) {
+    // Mingw64 rounds long double size and alignment up to 16 bytes, but sticks
+    // with x86 FP ops. Weird.
+    LongDoubleWidth = LongDoubleAlign = 128;
+    LongDoubleFormat = &llvm::APFloat::x87DoubleExtended;
+  }
+
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override {
     WindowsX86_64TargetInfo::getTargetDefines(Opts, Builder);