Re: [windows][rft] regparm vs stack probe fix

[Christopher Faylor <cgf at redhat dot com>]

On Mon, Oct 20, 2003 at 12:00:41AM -0700, Richard Henderson wrote:
>It would appear that we can just save and restore eax around the
>stack probe routine.  This looks good to my eye, but I don't have
>things set up to do testing on windows anywhere.

Since Danny says that this works for him, is it ok to check in?

cgf

>	* i386.c (ix86_eax_live_at_start_p): New.
>	(ix86_expand_prologue): Save and restore eax around stack probe
>	if it's live.
>
>Index: i386.c
>===================================================================
>RCS file: /cvs/gcc/gcc/gcc/config/i386/i386.c,v
>retrieving revision 1.609
>diff -c -p -d -r1.609 i386.c
>*** i386.c	19 Oct 2003 18:00:12 -0000	1.609
>--- i386.c	20 Oct 2003 06:54:27 -0000
>*************** ix86_function_regparm (tree type, tree d
>*** 1705,1710 ****
>--- 1705,1726 ----
>    return regparm;
>  }
>  
>+ /* Return true if EAX is live at the start of the function.  Used by 
>+    ix86_expand_prologue to determine if we need special help before
>+    calling allocate_stack_worker.  */
>+ 
>+ static bool
>+ ix86_eax_live_at_start_p (void)
>+ {
>+   /* Cheat.  Don't bother working forward from ix86_function_regparm
>+      to the function type to whether an actual argument is located in
>+      eax.  Instead just look at cfg info, which is still close enough
>+      to correct at this point.  This gives false positives for broken
>+      functions that might use uninitialized data that happens to be
>+      allocated in eax, but who cares?  */
>+   return REGNO_REG_SET_P (ENTRY_BLOCK_PTR->global_live_at_end, 0);
>+ }
>+ 
>  /* Value is the number of bytes of arguments automatically
>     popped when returning from a subroutine call.
>     FUNDECL is the declaration node of the function (as a tree),
>*************** ix86_expand_prologue (void)
>*** 5073,5092 ****
>      }
>    else
>      {
>!       /* Only valid for Win32 */
>! 
>!       const rtx eax = gen_rtx_REG (SImode, 0);
>!       rtx rtx_allocate = GEN_INT(allocate);
>  
>        if (TARGET_64BIT)
>          abort ();
>  
>!       insn = emit_move_insn (eax, rtx_allocate);
>        RTX_FRAME_RELATED_P (insn) = 1;
>  
>        insn = emit_insn (gen_allocate_stack_worker (eax));
>        RTX_FRAME_RELATED_P (insn) = 1;
>      }
>    if (frame.save_regs_using_mov && !TARGET_RED_ZONE)
>      {
>        if (!frame_pointer_needed || !frame.to_allocate)
>--- 5089,5120 ----
>      }
>    else
>      {
>!       /* Only valid for Win32.  */
>!       rtx eax = gen_rtx_REG (SImode, 0);
>!       bool eax_live = ix86_eax_live_at_start_p ();
>  
>        if (TARGET_64BIT)
>          abort ();
>  
>!       if (eax_live)
>! 	{
>! 	  emit_insn (gen_push (eax));
>! 	  allocate -= 4;
>! 	}
>! 
>!       insn = emit_move_insn (eax, GEN_INT (allocate));
>        RTX_FRAME_RELATED_P (insn) = 1;
>  
>        insn = emit_insn (gen_allocate_stack_worker (eax));
>        RTX_FRAME_RELATED_P (insn) = 1;
>+ 
>+       if (eax_live)
>+ 	{
>+ 	  rtx t = plus_constant (stack_pointer_rtx, allocate);
>+ 	  emit_move_insn (eax, gen_rtx_MEM (SImode, t));
>+ 	}
>      }
>+ 
>    if (frame.save_regs_using_mov && !TARGET_RED_ZONE)
>      {
>        if (!frame_pointer_needed || !frame.to_allocate)