i386.md: fp_jcc_3 and TARGET_CMOVE

[Clinton Popetz <cpopetz at cygnus dot com>]

Compiling the following:

	int 
	foo(double st)
	{
	  if (st)
	    return 0;
	}

with -march=i686 -O1 -ffast-math will give an ICE.  We'll get:

(jump_insn 12 11 29 (parallel[ 
            (set (pc)
                (if_then_else (eq:CCFP (reg/v:DF 8 st(0))
                        (mem/u:DF (symbol_ref/u:SI ("*.LC0")) 0))
                    (label_ref 21)
                    (pc)))
            (clobber (reg:CCFP 18 fpsr))
            (clobber (reg:CCFP 17 flags))
            (clobber (reg:HI 0 ax))
        ] ) 257 {*fp_jcc_3} (insn_list 4 (insn_list 4 (nil)))
    (expr_list:REG_DEAD (reg/v:DF 8 st(0))
        (expr_list:REG_UNUSED (reg:CCFP 18 fpsr)
            (expr_list:REG_UNUSED (reg:CCFP 17 flags)
                (nil)))))

which won't be split until final.  Then ix86_prepare_fp_compare_args
will see that ix86_use_fcomi_compare returns true and try to call
force_reg on the MEM, which we can't do that late.

I'm not sure of a good place to fix this.  The below patch works for
me.  Alternatively, ix86_use_fcomi_compare could be modified to check
the operands and return false if we need a new reg and no_new_pseudos
is set.  

				-Clint


Wed May 31 12:03:25 2000  Clinton Popetz  <cpopetz@cygnus.com>

	* config/i386/i386.c (ix86_use_fcomi_compare): Make global.
	* config/i386/i386-protos.h (ix86_use_fcomi_compare): Declare.
	* config/i386/i386.md (*fp_jcc_3): Require the second operand
	to be a REG if we can use FCOMI.


Index: i386-protos.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/i386/i386-protos.h,v
retrieving revision 1.19
diff -c -2 -p -r1.19 i386-protos.h
*** i386-protos.h	2000/04/27 14:56:46	1.19
--- i386-protos.h	2000/05/31 16:45:44
*************** extern int ix86_unary_operator_ok PARAMS
*** 100,103 ****
--- 100,104 ----
  extern int ix86_match_ccmode PARAMS ((rtx, enum machine_mode));
  extern rtx ix86_expand_fp_compare PARAMS ((enum rtx_code, rtx, rtx, rtx));
+ extern int ix86_use_fcomi_compare PARAMS ((enum rtx_code));
  extern void ix86_expand_branch PARAMS ((enum rtx_code, rtx));
  extern int ix86_expand_setcc PARAMS ((enum rtx_code, rtx));
Index: i386.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/i386/i386.c,v
retrieving revision 1.159
diff -c -2 -p -r1.159 i386.c
*** i386.c	2000/04/27 14:56:46	1.159
--- i386.c	2000/05/31 16:45:47
*************** static enum rtx_code unsigned_comparison
*** 393,397 ****
  static rtx ix86_expand_int_compare PARAMS ((enum rtx_code, rtx, rtx));
  static enum machine_mode ix86_fp_compare_mode PARAMS ((enum rtx_code));
- static int ix86_use_fcomi_compare PARAMS ((enum rtx_code));
  static enum rtx_code ix86_prepare_fp_compare_args PARAMS ((enum rtx_code,
  							   rtx *, rtx *));
--- 393,396 ----
*************** ix86_fp_compare_mode (code)
*** 4540,4544 ****
  /* Return true if we should use an FCOMI instruction for this fp comparison.  */
  
! static int
  ix86_use_fcomi_compare (code)
       enum rtx_code code;
--- 4539,4543 ----
  /* Return true if we should use an FCOMI instruction for this fp comparison.  */
  
! int
  ix86_use_fcomi_compare (code)
       enum rtx_code code;
Index: i386.md
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/i386/i386.md,v
retrieving revision 1.156
diff -c -2 -p -r1.156 i386.md
*** i386.md	2000/05/27 20:23:15	1.156
--- i386.md	2000/05/31 16:45:51
***************
*** 7154,7158 ****
    "TARGET_80387
     && (GET_MODE (operands[1]) == SFmode || GET_MODE (operands[1]) == DFmode)
!    && GET_MODE (operands[1]) == GET_MODE (operands[2])"
    "#")
  
--- 7154,7160 ----
    "TARGET_80387
     && (GET_MODE (operands[1]) == SFmode || GET_MODE (operands[1]) == DFmode)
!    && GET_MODE (operands[1]) == GET_MODE (operands[2])
!    && (GET_CODE (operands[2]) == REG || 
!        !ix86_use_fcomi_compare (GET_CODE (operands[0])))"
    "#")