[XCOFF] [DWARF] set default DWARF version to 3

[shchenz]

Summary

We support DWARF for XCOFF in D95518.

In this patch, we set the default DWARF version to 3 because the latest AIX OS supports DWARF version 3.

[jsji]

LGTM.

clang/lib/Driver/ToolChains/AIX.h

public:
 
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 
   CXXStdlibType GetDefaultCXXStdlibType() const override;
 
   RuntimeLibType GetDefaultRuntimeLibType() const override;
 
+  // Set default DWARF version to 3 for now as latest AIX OS supports version 3.
+  unsigned GetDefaultDwarfVersion() const override { return 3; }
+
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
 
 private:
   llvm::StringRef GetHeaderSysroot(const llvm::opt::ArgList &DriverArgs) const;
 };
 
 } // end namespace toolchains
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_AIX_H

clang/test/CodeGen/dwarf-version.c

 // RUN: %clang -target i686-pc-windows-msvc -gcodeview -S -emit-llvm -o - %s \
 // RUN:     | FileCheck %s --check-prefixes=NODWARF,CODEVIEW
 //     Explicitly request DWARF.
 // RUN: %clang -target i686-pc-windows-msvc -gdwarf -S -emit-llvm -o - %s \
 // RUN:     | FileCheck %s --check-prefixes=VER4,NOCODEVIEW
 //     Explicitly request both.
 // RUN: %clang -target i686-pc-windows-msvc -gdwarf -gcodeview -S -emit-llvm -o - %s \
 // RUN:     | FileCheck %s --check-prefixes=VER4,CODEVIEW
+// RUN: %clang -target powerpc-ibm-aix-xcoff -g -S -emit-llvm -o - %s | \
+// RUN:   FileCheck %s --check-prefix=VER3
+// RUN: %clang -target powerpc-ibm-aix-xcoff -gdwarf-2 -S -emit-llvm -o - %s | \
+// RUN:   FileCheck %s --check-prefix=VER2
+// RUN: %clang -target powerpc-ibm-aix-xcoff -gdwarf-3 -S -emit-llvm -o - %s | \
+// RUN:   FileCheck %s --check-prefix=VER3
+// RUN: %clang -target powerpc-ibm-aix-xcoff -gdwarf-4 -S -emit-llvm -o - %s | \
+// RUN:   FileCheck %s --check-prefix=VER4
+// RUN: %clang -target powerpc-ibm-aix-xcoff -gdwarf-5 -S -emit-llvm -o - %s | \
+// RUN:   FileCheck %s --check-prefix=VER5
+
 int main (void) {
   return 0;
 }
 
 // NOCODEVIEW-NOT: !"CodeView"
 
 // VER2: !{i32 7, !"Dwarf Version", i32 2}
 // VER3: !{i32 7, !"Dwarf Version", i32 3}
 // VER4: !{i32 7, !"Dwarf Version", i32 4}
 // VER5: !{i32 7, !"Dwarf Version", i32 5}
 
 // NODWARF-NOT: !"Dwarf Version"
 // CODEVIEW: !{i32 2, !"CodeView", i32 1}
 // NOCODEVIEW-NOT: !"CodeView"
 // NODWARF-NOT: !"Dwarf Version"