[Bug target/69274] [6 Regression] 435.gromacs performance regression after r231814 on x86 Haswell and bdver2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69274

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Alternate fix not causing PR69689 (but also not getting the extra speedup
observed with the original fix):

Index: gcc/ira.c
===================================================================
--- gcc/ira.c   (revision 233172)
+++ gcc/ira.c   (working copy)
@@ -1774,7 +1774,7 @@ ira_setup_alts (rtx_insn *insn, HARD_REG
   int nop, nalt;
   bool curr_swapped;
   const char *p;
-  int commutative = -1;
+  int commutative = -1, alt_commutative = -1;

   extract_insn (insn);
   alternative_mask preferred = get_preferred_alternatives (insn);
@@ -1838,6 +1838,8 @@ ira_setup_alts (rtx_insn *insn, HARD_REG

                  case '%':
                    /* The commutative modifier is handled above.  */
+                   if (alt_commutative < 0)
+                     alt_commutative = nop;
                    break;

                  case '0':  case '1':  case '2':  case '3':  case '4':
@@ -1889,10 +1891,13 @@ ira_setup_alts (rtx_insn *insn, HARD_REG
        }
       if (commutative < 0)
        break;
+      /* Swap forth and back to avoid changing recog_data.  */
+      if (! curr_swapped
+         || alt_commutative < 0)
+       std::swap (recog_data.operand[commutative],
+                  recog_data.operand[commutative + 1]);
       if (curr_swapped)
        break;
-      std::swap (recog_data.operand[commutative],
-                recog_data.operand[commutative + 1]);
     }
 }