http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60027

            Bug ID: 60027
           Summary: Problem with braced-init-lists and explicit ctors
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joaquin at tid dot es

The following code compiled with -std=c++11: 

struct foo 
{ 
  foo(int){} 
}; 

struct bar 
{ 
  explicit bar(int){} 
}; 

void f(foo){} 
void f(bar){} 

int main() 
{ 
  f({0}); 
} 

yields:

main.cpp:16:8: error: call of overloaded 'f(<brace-enclosed initializer
list>)' is ambiguous 
   f({0}); 
        ^ 
main.cpp:16:8: note: candidates are: 
main.cpp:11:6: note: void f(foo) 
 void f(foo){} 
      ^ 
main.cpp:12:6: note: void f(bar) 
 void f(bar){} 
      ^ 

which seems incorrect as bar::bar(int) is explicit.

Joaquín M López Muñoz
Telefónica Digital
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From: "wojtek.golf at interia dot pl" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/60028] New: TIC6X: B3 register (return address) is saved on stack when real call is replaced with sibling call in a leaf function
Date: Sun, 02 Feb 2014 11:29:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`028

            Bug ID: 60028
           Summary: TIC6X: B3 register (return address) is saved on stack
                    when real call is replaced with sibling call in a leaf
                    function
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wojtek.golf at interia dot pl

GCC 4.8.2, target tic6x
Input source:

int e_fun(int arg);
extern int e_int;

void g_fun(void)
{
    e_fun(e_int);
}

compiled with a command: -fleading-underscore -marchÆ74x -O2 -g0 -S main.c

gives the following assembler code:
_g_fun:
        sub .d2 B15, 8, B15
        stw .d2t2   B3, *+B15(8)
        b   .s1 (_e_fun)
    ||  ldw .d2t1   *+B14(_e_int), A4
        ldw .d2t2   *+B15(8), B3
    ||  add .s2 8, B15, B15
    ;; sibcall to (_e_fun) occurs
        nop 4

where B3 is saved on the stack even though a branch is taken to _e_fun. Texas
Instruments CGTools compiler v7.3.2 (cl6x --gcc -mv6740 --symdebug:none -k -n
main.c) gives the following assembler code (CALLRET is an alias to B):

_g_fun:
           CALLRET .S1     _e_fun            ; |6|
           LDW     .D2T1   *+DP(_e_int),A4   ; |6|
           NOP             4
$C$RL0:    ; CALL-RETURN OCCURS {_e_fun} 0   ; |6|

where B3 is not saved.

Some investigation on my part leads to the function c6x_expand_call in the file
gcc/gcc/config/c6x/c6x.c, where we see what may cause B3 being marked as used
and hence saved on the stack prior to the branch:

  if (sibcall)
    {
      call_insn = emit_call_insn (call_insn);
      use_reg (&CALL_INSN_FUNCTION_USAGE (call_insn),
         gen_rtx_REG (Pmode, REG_B3));
    }

commenting out use_reg invocation makes gcc to generate the expected listing:

_g_fun:
        b   .s1 (_e_fun)
    ||  ldw .d2t1   *+B14(_e_int), A4
    ;; sibcall to (_e_fun) occurs
        nop 5

I haven't tested yet whether removal of use_reg invocation causes any
regression, but I'd like it to be investigated whether it should be removed
altogether or protected with some extra execution condition.

With best,

Wojciech