[LLVMbugs] [Bug 13202] New: Clang duplicates debug info for inlined functions

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13202

             Bug #: 13202
           Summary: Clang duplicates debug info for inlined functions
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: samsonov at google.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Not sure yet if it's a clang or LLVM codegen bug.

$ cat inline-bug.cc 
#include <stdio.h>

static inline int ident(int argument) {
  int c = 0;
  printf("%d\n", c);
  return c;
}

int main() {
  return ident(0);
}
$ clang++ -g -O2 inline-bug.cc -S -emit-llvm
$ grep argument inline-bug.s 
!15 = metadata !{i32 786689, metadata !10, metadata !"argument", metadata !6,
i32 16777219, metadata !9, i32 0, i32 0} ; [ DW_TAG_arg_variable ]
!18 = metadata !{i32 786689, metadata !10, metadata !"argument", metadata !6,
i32 16777219, metadata !9, i32 0, metadata !19} ; [ DW_TAG_arg_variable ]

So, there are two metadata records for arg_variable "argument", one of which is
a reference to its inline location. However, generated dwarf contains two
identical records:
$ clang++ -g -O2 inline-bug.cc -o inline-bug.out
$ readelf -wi inline-bug.out
...
 <1><8c>: Abbrev Number: 8 (DW_TAG_subprogram)
    <8d>   DW_AT_MIPS_linkage_name: (indirect string, offset: 0x84): _ZL5identi 
    <91>   DW_AT_name        : (indirect string, offset: 0x8f): ident    
    <95>   DW_AT_decl_file   : 1    
    <96>   DW_AT_decl_line   : 3    
    <97>   DW_AT_type        : <0x85>    
    <9b>   DW_AT_inline      : 1    (inlined)
 <2><9c>: Abbrev Number: 9 (DW_TAG_formal_parameter)
    <9d>   DW_AT_name        : (indirect string, offset: 0x95): argument    
    <a1>   DW_AT_decl_file   : 1    
    <a2>   DW_AT_decl_line   : 3    
    <a3>   DW_AT_type        : <0x85>    
 <2><a7>: Abbrev Number: 9 (DW_TAG_formal_parameter)
    <a8>   DW_AT_name        : (indirect string, offset: 0x95): argument    
    <ac>   DW_AT_decl_file   : 1    
    <ad>   DW_AT_decl_line   : 3    
    <ae>   DW_AT_type        : <0x85>    
 <2><b2>: Abbrev Number: 10 (DW_TAG_lexical_block)
...
And they are interpreted as two identical parameters by, e.g., gdb:
$ gdb inline-bug.out
(gdb) start
Temporary breakpoint 1, main () at inline-bug.cc:10
10      return ident(0);
(gdb) step
ident (argument=<optimized out>, argument=<optimized out>) at inline-bug.cc:5
5      printf("%d\n", c);

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