[x86] Fix ICE with -fstack-check on Linux

[Eric Botcazou]

This is a regression present on the mainline and 4.7 branch.  The compiler 
ICEs on the attached Ada testcase at -O -fstack-check in ix86_expand_prologue:

  gcc_assert (m->fs.sp_offset == frame.stack_pointer_offset);

The problem is that release_scratch_register_on_entry uses a POP instruction 
but doesn't update cfun->machine accordingly.

Tested on x86_64-suse-linux, applied on mainline and 4.7 branch as obvious.


2012-11-09  Eric Botcazou  <ebotca...@adacore.com>

        * config/i386/i386.c (release_scratch_register_on_entry): Also adjust
        sp_offset manually.


2012-11-09  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/stack_check3.ad[sb]: New test.


-- 
Eric Botcazou
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 193322)
+++ config/i386/i386.c	(working copy)
@@ -9462,6 +9462,7 @@ release_scratch_register_on_entry (struc
 {
   if (sr->saved)
     {
+      struct machine_function *m = cfun->machine;
       rtx x, insn = emit_insn (gen_pop (sr->reg));
 
       /* The RTX_FRAME_RELATED_P mechanism doesn't know about pop.  */
@@ -9469,6 +9470,7 @@ release_scratch_register_on_entry (struc
       x = gen_rtx_PLUS (Pmode, stack_pointer_rtx, GEN_INT (UNITS_PER_WORD));
       x = gen_rtx_SET (VOIDmode, stack_pointer_rtx, x);
       add_reg_note (insn, REG_FRAME_RELATED_EXPR, x);
+      m->fs.sp_offset -= UNITS_PER_WORD;
     }
 }
 

-- { dg-do compile }
-- { dg-options "-O -fstack-check" }

package body Stack_Check3 is

  type Int_Arr is array (1 .. 34) of Integer;

  type Rec (D : Boolean := False) is
    record
      case D is
        when True  => IA : Int_Arr;
        when False => null;
      end case;
    end record;

  type Rec_Arr is array (1 .. 256) of Rec;

  protected Prot_Arr is
    procedure Reset;
  private
    A : Rec_Arr;
  end Prot_Arr;

  protected body Prot_Arr is
    procedure Reset is
    begin
      A := (others => (D => False));
    end Reset;
  end Prot_Arr;

  procedure Reset is
  begin
    Prot_Arr.Reset;
  end Reset;

end Stack_Check3;

package Stack_Check3 is

  procedure Reset;

end Stack_Check3;