[Bug tree-optimization/56547] [SH] missed opportunity for fmac with -ffast-math

["olegendo at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56547

Oleg Endo <olegendo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-05-16
          Component|target                      |tree-optimization
     Ever confirmed|0                           |1

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> ---
This looks like a tree optimization issue.
In tree-ssa-math-ops.c, the function 'convert_mult_to_fma' bails out in the
first for-each at:

      if (!is_gimple_assign (use_stmt))
    return false;


Apart from that, it still might be a good idea to put the SH fmac combine
patterns back, which I removed when adding support for the FMA patterns.
The following should do.


Index: gcc/config/sh/sh.md
===================================================================
--- gcc/config/sh/sh.md    (revision 198802)
+++ gcc/config/sh/sh.md    (working copy)
@@ -12285,6 +12285,29 @@
   "fmac.s %1, %2, %0"
   [(set_attr "type" "fparith_media")])

+;; For some cases such as 'a * b + a' the FMA pattern is not generated by
+;; previous transformations.  If FMA is generally allowed, let the combine
+;; pass utilize it.
+(define_insn "*fmasf4"
+   [(set (match_operand:SF 0 "fp_arith_reg_operand" "=f")
+    (plus:SF (mult:SF (match_operand:SF 1 "fp_arith_reg_operand" "%w")
+              (match_operand:SF 2 "fp_arith_reg_operand" "f"))
+         (match_operand:SF 3 "arith_reg_operand" "0")))
+    (use (match_operand:PSI 4 "fpscr_operand" "c"))]
+  "TARGET_SH2E && flag_fp_contract_mode != FP_CONTRACT_OFF"
+  "fmac    %1,%2,%0"
+  [(set_attr "type" "fp")
+   (set_attr "fp_mode" "single")])
+
+(define_insn "*fmasf4_media"
+  [(set (match_operand:SF 0 "fp_arith_reg_operand" "=f")
+    (plus:SF (mult:SF (match_operand:SF 1 "fp_arith_reg_operand" "%f")
+              (match_operand:SF 2 "fp_arith_reg_operand" "f"))
+         (match_operand:SF 3 "fp_arith_reg_operand" "0")))]
+  "TARGET_SHMEDIA_FPU && flag_fp_contract_mode != FP_CONTRACT_OFF"
+  "fmac.s %1, %2, %0"
+  [(set_attr "type" "fparith_media")])
+
 (define_expand "divsf3"
   [(set (match_operand:SF 0 "arith_reg_operand" "")
     (div:SF (match_operand:SF 1 "arith_reg_operand" "")