IAS: Use the root macro instanciation for location

[friss]

Summary

In r224810 you fixed the handling of debug locations in AsmParser. I think this
patch brings it closer to what you ireally wanted (or I misunderstood the logic
there): it uses the first macro of the macro stack instead of the last one. The
updated testcase shows that the current scheme doesn't work when macro
instanciations are nested and multiple files are used.

The case where '# <line> "<file>"' directives are present in the macro themselves
isn't handled by this patch, and I'm not sure we want it handled (what should the
behavior be?)

[compnerd]

Yeah, the change looks right. I think it would be better if you checked the debug info on the second case as well. Thanks for fixing my oversight!

[friss]

What do you mean by "checking the debug info on the other case as well" ? Also using directly the first macro and show that it still works?

llvm/trunk/lib/MC/MCParser/AsmParser.cpp

bool AsmParser::parseStatement(ParseStatementInfo &Info,
   // directive for the instruction.
   if (!HadError && getContext().getGenDwarfForAssembly() &&
       getContext().getGenDwarfSectionSyms().count(
           getStreamer().getCurrentSection().first)) {
     unsigned Line;
     if (ActiveMacros.empty())
       Line = SrcMgr.FindLineNumber(IDLoc, CurBuffer);
     else
-      Line = SrcMgr.FindLineNumber(ActiveMacros.back()->InstantiationLoc,
-                                   ActiveMacros.back()->ExitBuffer);
+      Line = SrcMgr.FindLineNumber(ActiveMacros.front()->InstantiationLoc,
+                                   ActiveMacros.front()->ExitBuffer);
 
     // If we previously parsed a cpp hash file line comment then make sure the
     // current Dwarf File is for the CppHashFilename if not then emit the
     // Dwarf File table for it and adjust the line number for the .loc.
     if (CppHashFilename.size()) {
       unsigned FileNumber = getStreamer().EmitDwarfFileDirective(
           0, StringRef(), CppHashFilename);
       getContext().setGenDwarfFileNumber(FileNumber);

llvm/trunk/test/DebugInfo/X86/asm-macro-line-number.s

 # RUN: llvm-mc -g -triple i686-linux-gnu -filetype asm -o - %s | FileCheck %s
 
 # 1 "reduced.S"
 # 1 "<built-in>" 1
 # 1 "reduced.S" 2
+# 200 "macros.h"
 
  .macro return arg
   movl %eax, \arg
   retl
  .endm
 
+ .macro return2 arg
+  return \arg
+ .endm
+
+# 7 "reduced.S"
 function:
  return 0
 
 # CHECK: .file 2 "reduced.S"
 # CHECK: .loc 2 8 0
 # CHECK: movl %eax, 0
 # CHECK: .loc 2 8 0
 # CHECK: retl
 
+# 42 "reduced.S"
+function2:
+ return2 0
+
+# CHECK: .loc 2 43 0
+# CHECK: movl %eax, 0
+# CHECK: .loc 2 43 0
+# CHECK: retl