[PATCH] Record the DWARF version in MCContext

[Oliver Stannard]

  Expand test/MC/ELF/gen-dwarf.s to check that the correct dwarf version is emitted.

http://reviews.llvm.org/D3399

CHANGE SINCE LAST DIFF
  http://reviews.llvm.org/D3399?vs=8569&id=8577#toc

Files:
  include/llvm/MC/MCContext.h
  lib/MC/MCDwarf.cpp
  test/MC/ELF/gen-dwarf.s
  tools/llvm-mc/llvm-mc.cpp

Index: include/llvm/MC/MCContext.h
===================================================================
--- include/llvm/MC/MCContext.h
+++ include/llvm/MC/MCContext.h
@@ -147,6 +147,9 @@
     /// non-empty.
     StringRef DwarfDebugProducer;
 
+    /// The maximum version of dwarf that we should emit.
+    unsigned DwarfVersion;
+
     /// Honor temporary labels, this is useful for debugging semantic
     /// differences between temporary and non-temporary labels (primarily on
     /// Darwin).
@@ -396,6 +399,9 @@
     void setDwarfDebugProducer(StringRef S) { DwarfDebugProducer = S; }
     StringRef getDwarfDebugProducer() { return DwarfDebugProducer; }
 
+    void setDwarfVersion(unsigned v) { DwarfVersion = v; }
+    unsigned getDwarfVersion() const { return DwarfVersion; }
+
     /// @}
 
     char *getSecureLogFile() { return SecureLogFile; }
Index: lib/MC/MCDwarf.cpp
===================================================================
--- lib/MC/MCDwarf.cpp
+++ lib/MC/MCDwarf.cpp
@@ -645,8 +645,8 @@
   const MCExpr *Length = MakeStartMinusEndExpr(*MCOS, *InfoStart, *InfoEnd, 4);
   MCOS->EmitAbsValue(Length, 4);
 
-  // The 2 byte DWARF version, which is 2.
-  MCOS->EmitIntValue(2, 2);
+  // The 2 byte DWARF version.
+  MCOS->EmitIntValue(context.getDwarfVersion(), 2);
 
   // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
   // it is at the start of that section so this is zero.
Index: test/MC/ELF/gen-dwarf.s
===================================================================
--- test/MC/ELF/gen-dwarf.s
+++ test/MC/ELF/gen-dwarf.s
@@ -1,5 +1,7 @@
-// RUN: llvm-mc -g -triple  i686-pc-linux-gnu %s -filetype=obj -o - | llvm-readobj -r | FileCheck %s
+// RUN: llvm-mc -g -dwarf-version 2 -triple  i686-pc-linux-gnu %s -filetype=obj -o - | llvm-readobj -r | FileCheck %s
 // RUN: llvm-mc -g -triple  i686-pc-linux-gnu %s -filetype=asm -o - | FileCheck --check-prefix=ASM %s
+// RUN: llvm-mc -g -dwarf-version 2 -triple  i686-pc-linux-gnu %s -filetype=asm -o - | FileCheck --check-prefix=ASM2 %s
+// RUN: llvm-mc -g -dwarf-version 3 -triple  i686-pc-linux-gnu %s -filetype=asm -o - | FileCheck --check-prefix=ASM3 %s
 
 
 // Test that on ELF:
@@ -34,8 +36,12 @@
 
 // Second instance of the section has the CU
 // ASM: .section .debug_info
+// ASM2: .section .debug_info
+// ASM3: .section .debug_info
 // Dwarf version
-// ASM: .short 2
+// ASM2: .short 2
+// ASM3: .short 3
+// ASM: .short 4
 // ASM-NEXT: .long [[ABBREV_LABEL]]
 // First .byte 1 is the abbreviation number for the compile_unit abbrev
 // ASM: .byte 1
Index: tools/llvm-mc/llvm-mc.cpp
===================================================================
--- tools/llvm-mc/llvm-mc.cpp
+++ tools/llvm-mc/llvm-mc.cpp
@@ -153,6 +153,9 @@
 GenDwarfForAssembly("g", cl::desc("Generate dwarf debugging info for assembly "
                                   "source files"));
 
+static cl::opt<int>
+DwarfVersion("dwarf-version", cl::desc("Dwarf version"), cl::init(4));
+
 static cl::opt<std::string>
 DebugCompilationDir("fdebug-compilation-dir",
                     cl::desc("Specifies the debug info's compilation dir"));
@@ -403,6 +406,12 @@
     Ctx.setAllowTemporaryLabels(false);
 
   Ctx.setGenDwarfForAssembly(GenDwarfForAssembly);
+  if (DwarfVersion < 2 || DwarfVersion > 4) {
+    errs() << ProgName << ": Dwarf version " << DwarfVersion
+           << " is not supported." << '\n';
+    return 1;
+  }
+  Ctx.setDwarfVersion(DwarfVersion);
   if (!DwarfDebugFlags.empty())
     Ctx.setDwarfDebugFlags(StringRef(DwarfDebugFlags));
   if (!DwarfDebugProducer.empty())
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