[patch] Enable fmove-loop-invariants by default

[Zdenek Dvorak]

Hello,

> > this patch enables the new loop invariant motion pass by default.  This
> > duplicates functionality of loop.c, but I still hope loop.c will be
> > removed soon, and even if not, it is neccessary to have loop-invariant
> > tested if we ever want to use it (I have just spent a week by fixing
> > bugs introduced because it was disabled and nobody tested it).
> 
> It may badly interact with -fnon-call-exceptions, causing 
> 
> FAIL:   cxg2007
> FAIL:   cxg2012
> 
> to pop up in the ACATS testsuite on x86-64/Linux.
> 
> 
> cxg2007.adb: In function 'CXG2007':
> cxg2007.adb:228: error: missing REG_EH_REGION note in the end of bb 162
> +===========================GNAT BUG DETECTED==============================+
> | 4.2.0 20060213 (experimental) (x86_64-suse-linux-gnu) GCC error:         |
> | verify_flow_info failed                                                  |
> | Error detected at cxg2007.adb:228:5              
> 
> (insn 1065 1063 1696 162 (set (mem:XF (plus:DI (reg/f:DI 7 sp)
>                 (const_int 64 [0x40])) [0 S16 A64])
>         (const_double:XF 3.0e+0 [0x0.cp+2])) 99 {*movxf_integer} (nil)
>     (expr_list:REG_EH_REGION (const_int 21 [0x15])
>         (nil)))
> ;; End of basic block 162, registers live:
>  (nil)
> 
> Set in insn 1065 is invariant (29), cost 6, depends on 
> 
> Decided to move invariant 29
> 
> 
> I'm not sure what the counter-measures were in loop.c against that.  Do you 
> see any other straightforward solutions than punting in that case?

something like this should help.

Zdenek

Index: loop-invariant.c
===================================================================
*** loop-invariant.c	(revision 110963)
--- loop-invariant.c	(working copy)
*************** Software Foundation, 51 Franklin Street,
*** 52,57 ****
--- 52,58 ----
  #include "flags.h"
  #include "df.h"
  #include "hashtab.h"
+ #include "except.h"
  
  /* The data stored for the loop.  */
  
*************** find_invariant_insn (rtx insn, bool alwa
*** 761,776 ****
        || !check_maybe_invariant (SET_SRC (set)))
      return;
  
!   if (may_trap_p (PATTERN (insn)))
!     {
!       if (!always_reached)
! 	return;
  
!       /* Unless the exceptions are handled, the behavior is undefined
!  	 if the trap occurs.  */
!       if (flag_non_call_exceptions)
! 	return;
!     }
  
    depends_on = BITMAP_ALLOC (NULL);
    if (!check_dependencies (insn, depends_on))
--- 762,775 ----
        || !check_maybe_invariant (SET_SRC (set)))
      return;
  
!   /* If the insn can throw exception, we cannot move it at all without changing
!      cfg.  */
!   if (can_throw_internal (insn))
!     return;
  
!   /* We cannot make trapping insn executed, unless it was executed before.  */
!   if (may_trap_p (PATTERN (insn)) && !always_reached)
!     return;
  
    depends_on = BITMAP_ALLOC (NULL);
    if (!check_dependencies (insn, depends_on))
Index: Makefile.in
===================================================================
*** Makefile.in	(revision 110964)
--- Makefile.in	(working copy)
*************** loop-iv.o : loop-iv.c $(CONFIG_H) $(SYST
*** 2423,2429 ****
  loop-invariant.o : loop-invariant.c $(CONFIG_H) $(SYSTEM_H) $(RTL_H) \
     $(BASIC_BLOCK_H) hard-reg-set.h $(CFGLOOP_H) $(EXPR_H) coretypes.h \
     $(TM_H) $(TM_P_H) $(FUNCTION_H) $(FLAGS_H) $(DF_H) $(OBSTACK_H) output.h \
!    $(HASHTAB_H)
  cfgloopmanip.o : cfgloopmanip.c $(CONFIG_H) $(SYSTEM_H) $(RTL_H) \
     $(BASIC_BLOCK_H) hard-reg-set.h $(CFGLOOP_H) $(CFGLAYOUT_H) output.h \
     coretypes.h $(TM_H) cfghooks.h $(OBSTACK_H)
--- 2423,2429 ----
  loop-invariant.o : loop-invariant.c $(CONFIG_H) $(SYSTEM_H) $(RTL_H) \
     $(BASIC_BLOCK_H) hard-reg-set.h $(CFGLOOP_H) $(EXPR_H) coretypes.h \
     $(TM_H) $(TM_P_H) $(FUNCTION_H) $(FLAGS_H) $(DF_H) $(OBSTACK_H) output.h \
!    $(HASHTAB_H) except.h
  cfgloopmanip.o : cfgloopmanip.c $(CONFIG_H) $(SYSTEM_H) $(RTL_H) \
     $(BASIC_BLOCK_H) hard-reg-set.h $(CFGLOOP_H) $(CFGLAYOUT_H) output.h \
     coretypes.h $(TM_H) cfghooks.h $(OBSTACK_H)