We want the dwarf AT_producer for assembly source files to match clang's

AT_producer.  Which includes clang's version information so we can tell
which version of the compiler was used.

This is the first of two steps to allow us to do that.  This is the llvm-mc
change to provide a method to set the AT_producer string.  The second step,
coming soon to a clang near you, will have the clang driver pass the value
of getClangFullVersion() via an flag when invoking the integrated assembler
on assembly source files.

rdar://12955296


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172630 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCContext.h

@@ -129,6 +129,10 @@ namespace llvm {
     /// non-empty.
     StringRef DwarfDebugFlags;
 
+    /// The string to embed in as the dwarf AT_producer for the compile unit, if
+    /// non-empty.
+    StringRef DwarfDebugProducer;
+
     /// Honor temporary labels, this is useful for debugging semantic
     /// differences between temporary and non-temporary labels (primarily on
     /// Darwin).
@@ -346,6 +350,9 @@ namespace llvm {
     void setDwarfDebugFlags(StringRef S) { DwarfDebugFlags = S; }
     StringRef getDwarfDebugFlags() { return DwarfDebugFlags; }
 
+    void setDwarfDebugProducer(StringRef S) { DwarfDebugProducer = S; }
+    StringRef getDwarfDebugProducer() { return DwarfDebugProducer; }
+
     /// @}
 
     char *getSecureLogFile() { return SecureLogFile; }

lib/MC/MCDwarf.cpp

@@ -638,9 +638,15 @@ static void EmitGenDwarfInfo(MCStreamer *MCOS,
   }
 
   // AT_producer, the version of the assembler tool.
-  MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM "));
-  MCOS->EmitBytes(StringRef(PACKAGE_VERSION));
-  MCOS->EmitBytes(StringRef(")"));
+  StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
+  if (!DwarfDebugProducer.empty()){
+    MCOS->EmitBytes(DwarfDebugProducer);
+  }
+  else {
+    MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM "));
+    MCOS->EmitBytes(StringRef(PACKAGE_VERSION));
+    MCOS->EmitBytes(StringRef(")"));
+  }
   MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
 
   // AT_language, a 4 byte value.  We use DW_LANG_Mips_Assembler as the dwarf2

test/MC/MachO/gen-dwarf-producer.s

@@ -0,0 +1,8 @@
+// RUN: env DEBUG_PRODUCER="my producer" llvm-mc -g -triple i386-apple-darwin10 %s -filetype=obj -o %t
+// RUN: llvm-dwarfdump %t | FileCheck %s
+
+.globl _bar
+_bar:
+	ret
+
+// CHECK:    DW_AT_producer [DW_FORM_string]	("my producer")

tools/llvm-mc/llvm-mc.cpp

@@ -236,6 +236,13 @@ static void setDwarfDebugFlags(int argc, char **argv) {
   }
 }
 
+static std::string DwarfDebugProducer;
+static void setDwarfDebugProducer(void) {
+  if(!getenv("DEBUG_PRODUCER"))
+    return;
+  DwarfDebugProducer += getenv("DEBUG_PRODUCER");
+}
+
 static int AsLexInput(SourceMgr &SrcMgr, MCAsmInfo &MAI, tool_output_file *Out) {
 
   AsmLexer Lexer(MAI);
@@ -353,6 +360,8 @@ int main(int argc, char **argv) {
   TripleName = Triple::normalize(TripleName);
   setDwarfDebugFlags(argc, argv);
 
+  setDwarfDebugProducer();
+
   const char *ProgName = argv[0];
   const Target *TheTarget = GetTarget(ProgName);
   if (!TheTarget)
@@ -393,6 +402,8 @@ int main(int argc, char **argv) {
   Ctx.setGenDwarfForAssembly(GenDwarfForAssembly);
   if (!DwarfDebugFlags.empty())
     Ctx.setDwarfDebugFlags(StringRef(DwarfDebugFlags));
+  if (!DwarfDebugProducer.empty())
+    Ctx.setDwarfDebugProducer(StringRef(DwarfDebugProducer));
   if (!DebugCompilationDir.empty())
     Ctx.setCompilationDir(DebugCompilationDir);
   if (!MainFileName.empty())