IAS: Use the root macro instanciation for location

r224810 fixed the handling of macro debug locations in AsmParser. This patch
fixes the logic to actually do what was intended: 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.

Reviewers: compnerd

Differential Revision: http://reviews.llvm.org/D10463

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240705 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCParser/AsmParser.cpp

@@ -1646,8 +1646,8 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
     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

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

@@ -3,12 +3,18 @@
 # 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
 
@@ -18,3 +24,11 @@ function:
 # 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