Re: [patch] Fix problematic debug info for parameters at -O0

[Eric Botcazou]

> The testcase doesn't necessarily need to FAIL without the patch on x86, it
> is fine if it fails on some PowerPC* or Visium.

Here's what I have installed on mainline and 6 branch (not sure it's worth 
fixing on the aging 5 branch).  The test fails on PowerPC/Linux:

(gdb) b param-5.c:26
Breakpoint 1 at 0x10000510: file param-5.c, line 26.
(gdb) run
Starting program: /nfs/tron/work/botcazou/gcc-head/powerpc-linux-gnu/param-5 

Breakpoint 1, foo (
    str=<error reading variable: Cannot access memory at address 0xffffffc8>, 
    count=0) at param-5.c:26
26        count--;  /* BREAK */
(gdb) bt
#0  foo (
    str=<error reading variable: Cannot access memory at address 0xffffffc8>, 
    count=0) at param-5.c:26
#1  0x1000050c in foo (
    str=<error reading variable: value has been optimized out>, count=1)
    at param-5.c:24
#2  0x10000590 in main () at param-5.c:33


2016-06-22  Eric Botcazou  <ebotca...@adacore.com>

        * function.c (assign_parm_setup_reg): Prevent sharing in another case.


2016-06-22  Eric Botcazou  <ebotca...@adacore.com>

        * gcc.dg/guality/param-5.c: New test.

-- 
Eric Botcazou
Index: function.c
===================================================================
--- function.c	(revision 237677)
+++ function.c	(working copy)
@@ -3314,6 +3314,8 @@ assign_parm_setup_reg (struct assign_par
 	  set_mem_attributes (parmreg, parm, 1);
 	}
 
+      /* We need to preserve an address based on VIRTUAL_STACK_VARS_REGNUM for
+	 the debug info in case it is not legitimate.  */
       if (GET_MODE (parmreg) != GET_MODE (rtl))
 	{
 	  rtx tempreg = gen_reg_rtx (GET_MODE (rtl));
@@ -3323,7 +3325,8 @@ assign_parm_setup_reg (struct assign_par
 			     all->last_conversion_insn);
 	  emit_move_insn (tempreg, rtl);
 	  tempreg = convert_to_mode (GET_MODE (parmreg), tempreg, unsigned_p);
-	  emit_move_insn (parmreg, tempreg);
+	  emit_move_insn (MEM_P (parmreg) ? copy_rtx (parmreg) : parmreg,
+			  tempreg);
 	  all->first_conversion_insn = get_insns ();
 	  all->last_conversion_insn = get_last_insn ();
 	  end_sequence ();
@@ -3331,7 +3334,7 @@ assign_parm_setup_reg (struct assign_par
 	  did_conversion = true;
 	}
       else
-	emit_move_insn (parmreg, rtl);
+	emit_move_insn (MEM_P (parmreg) ? copy_rtx (parmreg) : parmreg, rtl);
 
       rtl = parmreg;
 

/* { dg-do run } */
/* { dg-options "-g" } */
/* { dg-skip-if "" { *-*-* }  { "*" } { "-O0" } } */

typedef __UINTPTR_TYPE__ uintptr_t;

typedef struct { uintptr_t pa; uintptr_t pb; } fatp_t
  __attribute__ ((aligned (2 * __alignof__ (uintptr_t))));

__attribute__((noinline, noclone)) void
clear_stack (void)
{
  char a[128 * 1024 + 128];

  __builtin_memset (a, 0, sizeof (a));
}

__attribute__((noinline, noclone)) void
foo (fatp_t str, int count)
{
  char a[128 * 1024];

  if (count > 0)
    foo (str, count - 1);
  clear_stack ();
  count--;  /* BREAK */
}

int
main (void)
{
  fatp_t ptr = { 31415927, 27182818 };
  foo (ptr, 1);
  return 0;
}

/* { dg-final { gdb-test 26 "str.pa" "31415927" } } */
/* { dg-final { gdb-test 26 "str.pb" "27182818" } } */