[PowerPC] Emit IR module flag for current float abi

This is part of the efforts adding .gnu_attribute support for PowerPC.
In Clang, an extra metadata field will be added as float-abi to show
current long double format. So backend can emit .gnu_attribute section
data from this metadata.

To avoid breaking existing behavior, the module metadata will only be
emitted when this module makes use of long double.

Reviewed By: nemanjai

Differential Revision: https://reviews.llvm.org/D116016

Author: ecnelises

clang/lib/CodeGen/CodeGenTypes.cpp

@@ -34,6 +34,7 @@ CodeGenTypes::CodeGenTypes(CodeGenModule &cgm)
     Target(cgm.getTarget()), TheCXXABI(cgm.getCXXABI()),
     TheABIInfo(cgm.getTargetCodeGenInfo().getABIInfo()) {
   SkippedLayout = false;
+  LongDoubleReferenced = false;
 }
 
 CodeGenTypes::~CodeGenTypes() {
@@ -406,10 +407,12 @@ llvm::Type *CodeGenTypes::ConvertType(QualType T) {
           Context.getLangOpts().NativeHalfType ||
               !Context.getTargetInfo().useFP16ConversionIntrinsics());
       break;
+    case BuiltinType::LongDouble:
+      LongDoubleReferenced = true;
+      LLVM_FALLTHROUGH;
     case BuiltinType::BFloat16:
     case BuiltinType::Float:
     case BuiltinType::Double:
-    case BuiltinType::LongDouble:
     case BuiltinType::Float128:
     case BuiltinType::Ibm128:
       ResultType = getTypeForFormat(getLLVMContext(),

clang/lib/CodeGen/CodeGenTypes.h

@@ -84,6 +84,9 @@ class CodeGenTypes {
   /// a recursive struct conversion, set this to true.
   bool SkippedLayout;
 
+  /// True if any instance of long double types are used.
+  bool LongDoubleReferenced;
+
   /// This map keeps cache of llvm::Types and maps clang::Type to
   /// corresponding llvm::Type.
   llvm::DenseMap<const Type *, llvm::Type *> TypeCache;
@@ -289,6 +292,7 @@ class CodeGenTypes {
   /// zero-initialized (in the C++ sense) with an LLVM zeroinitializer.
   bool isZeroInitializable(const RecordDecl *RD);
 
+  bool isLongDoubleReferenced() const { return LongDoubleReferenced; }
   bool isRecordLayoutComplete(const Type *Ty) const;
   unsigned getTargetAddressSpace(QualType T) const;
 };

clang/lib/CodeGen/Targets/PPC.cpp

@@ -620,6 +620,9 @@ class PPC64_SVR4_TargetCodeGenInfo : public TargetCodeGenInfo {
 
   bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
                                llvm::Value *Address) const override;
+  void emitTargetMetadata(CodeGen::CodeGenModule &CGM,
+                          const llvm::MapVector<GlobalDecl, StringRef>
+                              &MangledDeclNames) const override;
 };
 
 class PPC64TargetCodeGenInfo : public TargetCodeGenInfo {
@@ -940,6 +943,24 @@ PPC64_SVR4_TargetCodeGenInfo::initDwarfEHRegSizeTable(
                                      /*IsAIX*/ false);
 }
 
+void PPC64_SVR4_TargetCodeGenInfo::emitTargetMetadata(
+    CodeGen::CodeGenModule &CGM,
+    const llvm::MapVector<GlobalDecl, StringRef> &MangledDeclNames) const {
+  if (CGM.getTypes().isLongDoubleReferenced()) {
+    llvm::LLVMContext &Ctx = CGM.getLLVMContext();
+    const auto *flt = &CGM.getTarget().getLongDoubleFormat();
+    if (flt == &llvm::APFloat::PPCDoubleDouble())
+      CGM.getModule().addModuleFlag(llvm::Module::Error, "float-abi",
+                                    llvm::MDString::get(Ctx, "doubledouble"));
+    else if (flt == &llvm::APFloat::IEEEquad())
+      CGM.getModule().addModuleFlag(llvm::Module::Error, "float-abi",
+                                    llvm::MDString::get(Ctx, "ieeequad"));
+    else if (flt == &llvm::APFloat::IEEEdouble())
+      CGM.getModule().addModuleFlag(llvm::Module::Error, "float-abi",
+                                    llvm::MDString::get(Ctx, "ieeedouble"));
+  }
+}
+
 bool
 PPC64TargetCodeGenInfo::initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
                                                 llvm::Value *Address) const {

clang/test/CodeGen/ppc64-float-abi-attr.c

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple powerpc64le-unknown-linux-gnu %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple powerpc64le-unknown-linux-gnu %s -emit-llvm -mabi=ieeelongdouble -o - | FileCheck %s --check-prefix=IEEE
+// RUN: %clang_cc1 -triple powerpc64le-unknown-linux-gnu %s -emit-llvm -mlong-double-64 -o - | FileCheck %s --check-prefix=LDBL64
+// RUN: %clang_cc1 -triple powerpc64le-unknown-linux-gnu %s -emit-llvm -DNOLDBL -o - | FileCheck %s --check-prefix=NOLDBL
+
+#ifndef NOLDBL
+long double foo(long double a, long double b) {
+  return a + b;
+}
+#endif
+
+int bar() { return 1; }
+
+// CHECK: ![[#]] = !{i32 1, !"float-abi", !"doubledouble"}
+// IEEE: ![[#]] = !{i32 1, !"float-abi", !"ieeequad"}
+// LDBL64: ![[#]] = !{i32 1, !"float-abi", !"ieeedouble"}
+// NOLDBL-NOT: ![[#]] = !{i32 1, !"float-abi"