alpha tfmode tweeks

[Richard Henderson <rth at cygnus dot com>]

* I'd twiddled the wrong word on negtf and abstf
* extendsftf is not synthesized by optabs
* Use alternate method for trunctfsf that doesn't incorrectly round.


r~


        * alpha.md (negtf2, abstf2): Fix word order thinko.
        (extendsftf2): New.
        (trunctfsf2): Avoid intermediate rounding errors.

Index: alpha.md
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/alpha/alpha.md,v
retrieving revision 1.107
diff -c -p -d -r1.107 alpha.md
*** alpha.md	2000/01/28 04:36:43	1.107
--- alpha.md	2000/01/30 20:11:24
***************
*** 1808,1825 ****
    move = 1;
    if (rtx_equal_p (operands[0], operands[2]))
      move = 0;
!   else if (rtx_equal_p (operands[0], operands[3]))
      move = -1;
  
    if (move < 0)
!     emit_move_insn (operands[1], operands[3]);
  
    tmp = gen_rtx_NOT (DImode, operands[4]);
!   tmp = gen_rtx_AND (DImode, tmp, operands[2]);
!   emit_insn (gen_rtx_SET (VOIDmode, operands[0], tmp));
  	
    if (move > 0)
!     emit_move_insn (operands[1], operands[3]);
    DONE;
  }")
  
--- 1808,1825 ----
    move = 1;
    if (rtx_equal_p (operands[0], operands[2]))
      move = 0;
!   else if (rtx_equal_p (operands[1], operands[2]))
      move = -1;
  
    if (move < 0)
!     emit_move_insn (operands[0], operands[2]);
  
    tmp = gen_rtx_NOT (DImode, operands[4]);
!   tmp = gen_rtx_AND (DImode, tmp, operands[3]);
!   emit_insn (gen_rtx_SET (VOIDmode, operands[1], tmp));
  	
    if (move > 0)
!     emit_move_insn (operands[0], operands[2]);
    DONE;
  }")
  
***************
*** 1873,1888 ****
    move = 1;
    if (rtx_equal_p (operands[0], operands[2]))
      move = 0;
!   else if (rtx_equal_p (operands[0], operands[3]))
      move = -1;
  
    if (move < 0)
!     emit_move_insn (operands[1], operands[3]);
  
!   emit_insn (gen_xordi3 (operands[0], operands[2], operands[4]));
  	
    if (move > 0)
!     emit_move_insn (operands[1], operands[3]);
    DONE;
  }")
  
--- 1873,1888 ----
    move = 1;
    if (rtx_equal_p (operands[0], operands[2]))
      move = 0;
!   else if (rtx_equal_p (operands[1], operands[2]))
      move = -1;
  
    if (move < 0)
!     emit_move_insn (operands[0], operands[2]);
  
!   emit_insn (gen_xordi3 (operands[1], operands[3], operands[4]));
  	
    if (move > 0)
!     emit_move_insn (operands[0], operands[2]);
    DONE;
  }")
  
***************
*** 2179,2184 ****
--- 2179,2196 ----
     st%- %1,%0"
    [(set_attr "type" "fcpys,fld,fst")])
  
+ (define_expand "extendsftf2"
+   [(use (match_operand:TF 0 "register_operand" ""))
+    (use (match_operand:SF 1 "general_operand" ""))]
+   "TARGET_HAS_XFLOATING_LIBS"
+   "
+ {
+   rtx tmp = gen_reg_rtx (DFmode);
+   emit_insn (gen_extendsfdf2 (tmp, operands[1]));
+   emit_insn (gen_extenddftf2 (operands[0], tmp));
+   DONE;
+ }")
+ 
  (define_expand "extenddftf2"
    [(use (match_operand:TF 0 "register_operand" ""))
     (use (match_operand:DF 1 "general_operand" ""))]
***************
*** 2207,2225 ****
    "TARGET_HAS_XFLOATING_LIBS"
    "alpha_emit_xfloating_cvt (FLOAT_TRUNCATE, operands); DONE;")
  
- ;; ??? This isn't quite right, as rounding isn't correct.  But it's
- ;; extremely tortureous to do this correctly with the functionality
- ;; availible in the library.
- 
  (define_expand "trunctfsf2"
    [(use (match_operand:SF 0 "register_operand" ""))
     (use (match_operand:TF 1 "general_operand" ""))]
    "TARGET_HAS_XFLOATING_LIBS"
    "
  {
!   rtx tmp = gen_reg_rtx (DFmode);
!   emit_insn (gen_trunctfdf2 (tmp, operands[1]));
!   emit_insn (gen_truncdfsf2 (operands[0], tmp));
    DONE;
  }")
  
--- 2219,2248 ----
    "TARGET_HAS_XFLOATING_LIBS"
    "alpha_emit_xfloating_cvt (FLOAT_TRUNCATE, operands); DONE;")
  
  (define_expand "trunctfsf2"
    [(use (match_operand:SF 0 "register_operand" ""))
     (use (match_operand:TF 1 "general_operand" ""))]
    "TARGET_HAS_XFLOATING_LIBS"
    "
  {
!   rtx tmpf, sticky, arg, lo, hi;
! 
!   tmpf = gen_reg_rtx (DFmode);
!   sticky = gen_reg_rtx (DImode);
!   arg = copy_to_mode_reg (TFmode, operands[1]);
!   lo = gen_lowpart (DImode, arg);
!   hi = gen_highpart (DImode, arg);
! 
!   /* Convert the low word of the TFmode value into a sticky rounding bit,
!      then or it into the low bit of the high word.  This leaves the sticky
!      bit at bit 48 of the fraction, which is representable in DFmode,
!      which prevents rounding error in the final conversion to SFmode.  */
! 
!   emit_insn (gen_rtx_SET (VOIDmode, sticky, 
! 			  gen_rtx_LTU (DImode, const0_rtx, lo)));
!   emit_insn (gen_iordi3 (hi, hi, sticky));
!   emit_insn (gen_trunctfdf2 (tmpf, arg));
!   emit_insn (gen_truncdfsf2 (operands[0], tmpf));
    DONE;
  }")