Re: ping Zdenek's patch for 17428

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> On Sun, 13 Feb 2005, Zdenek Dvorak wrote:
> > I believe that most of the time no hard register at all should be live
> > at the point where the insertion happens.  This is the reason why I did
> > not want to make things more complicated than necessary.  Simply
> > disabling the optimization in case any hard reg is live at the point
> > would IMHO work as well.
> 
> That certainly simplifies things.  Could you collect some statistics
> on what fraction of the calls to safe_insert_insn_on_edge have a live
> non-fixed hard regsiter, and if so how many?  If, as you suggest, the
> majority of the time there are no live registers, and when there are
> we only spill one or two, then the patch may be fine as it is.

with the following minor modification of the patch (the
!REGNO_PTR_FRAME_P condition to avoid saving ebp) we get the following
numbers of extra registers saved (on athlon and partial boostrap of
gcc):

32958 times 0
26 times 1
21 times 2
24 times 3
		 
Zdenek

Index: cfgrtl.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cfgrtl.c,v
retrieving revision 1.157
diff -c -3 -p -r1.157 cfgrtl.c
*** cfgrtl.c	6 Jan 2005 18:05:27 -0000	1.157
--- cfgrtl.c	13 Feb 2005 22:23:41 -0000
*************** safe_insert_insn_on_edge (rtx insn, edge
*** 1470,1475 ****
--- 1470,1485 ----
    for (x = insn; x; x = NEXT_INSN (x))
      if (INSN_P (x))
        note_stores (PATTERN (x), mark_killed_regs, killed);
+ 
+   /* Mark all hard registers as killed.  Register allocator/reload cannot
+      cope with the situation when life range of hard register spans operation
+      for that the appropriate register is needed, i.e. it would be unsafe to
+      extend the life ranges of hard registers.  */
+   for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+     if (!fixed_regs[regno]
+ 	&& !REGNO_PTR_FRAME_P (regno))
+       SET_REGNO_REG_SET (killed, regno);
+ 
    bitmap_and_into (killed, e->dest->global_live_at_start);
  
    EXECUTE_IF_SET_IN_REG_SET (killed, 0, regno, rsi)
Index: value-prof.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/value-prof.c,v
retrieving revision 1.16
diff -c -3 -p -r1.16 value-prof.c
*** value-prof.c	14 Nov 2004 23:35:03 -0000	1.16
--- value-prof.c	13 Feb 2005 22:23:41 -0000
*************** insn_prefetch_values_to_profile (rtx ins
*** 245,251 ****
    int write;
    histogram_value hist;
  
!   if (!INSN_P (insn))
      return false;
  
    if (!find_mem_reference (insn, &mem, &write))
--- 245,252 ----
    int write;
    histogram_value hist;
  
!   /* It only makes sense to look for memory references in ordinary insns.  */
!   if (GET_CODE (insn) != INSN)
      return false;
  
    if (!find_mem_reference (insn, &mem, &write))