loop.c (check_dbra_loop): A store using an address giv for which we have no life...

        1999-02-05  Michael Meissner  <meissner@cygnus.com>
                    J"orn Rennecke <amylaar@cygnus.co.uk>
        * loop.c (check_dbra_loop): A store using an address giv for which
        we have no life information is not reversible.
        * loop.c (first_loop_store_insn): New file-scope variable.
        (prescan_loop): Set it.
        (check_dbra_loop): Check if a store depends on a register
        that is set after the store.

From-SVN: r25181

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1d439076f52e546cf32e0e8c3ca2643d9404b6f7..24e25d1895e2cc8b4d611860c3d8e31699ebc3a7 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 Sat Feb 13 11:53:12 1999  Jeffrey A Law  (law@cygnus.com)
 
+       1999-02-05  Michael Meissner  <meissner@cygnus.com>
+                   J"orn Rennecke <amylaar@cygnus.co.uk>
+       * loop.c (check_dbra_loop): A store using an address giv for which
+       we have no life information is not reversible.
+       * loop.c (first_loop_store_insn): New file-scope variable.
+       (prescan_loop): Set it.
+       (check_dbra_loop): Check if a store depends on a register
+       that is set after the store.
+
        Sun Jan 31 13:22:02 1999  John Wehle  (john@feith.com)
        * i386.md (movsicc, movhicc, movsfcc, movdfcc,
        movxfcc, movdicc): Delete unconstrained alternatives.

diff --git a/gcc/loop.c b/gcc/loop.c
index 097dccf046fe03524bb347ab4396a8449683697d..5e021812206bc5858235c7361cd7d34159b548b9 100644 (file)
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -195,6 +195,9 @@ static rtx loop_store_mems[NUM_STORES];
 /* Index of first available slot in above array.  */
 static int loop_store_mems_idx;
 
+/* The insn where the first of these was found.  */
+static rtx first_loop_store_insn;
+
 /* Nonzero if we don't know what MEMs were changed in the current loop.
    This happens if the loop contains a call (in which case `loop_has_call'
    will also be set) or if we store into more than NUM_STORES MEMs.  */
@@ -2288,6 +2291,7 @@ prescan_loop (start, end)
   unknown_address_altered = 0;
   loop_has_call = 0;
   loop_has_volatile = 0;
+  first_loop_store_insn = NULL_RTX;
   loop_store_mems_idx = 0;
 
   num_mem_sets = 0;
@@ -2334,6 +2338,9 @@ prescan_loop (start, end)
                loop_has_volatile = 1;
 
              note_stores (PATTERN (insn), note_addr_stored);
+             if (! first_loop_store_insn && loop_store_mems_idx != 0)
+               first_loop_store_insn = insn;
+
            }
        }
     }
@@ -6274,9 +6281,26 @@ check_dbra_loop (loop_end, insn_count, loop_start)
         case, the insn should have been moved out of the loop.  */
 
       if (num_mem_sets == 1)
-       reversible_mem_store
-         = (! unknown_address_altered
-            && ! invariant_p (XEXP (loop_store_mems[0], 0)));
+       {
+         struct induction *v;
+
+         reversible_mem_store
+           = (! unknown_address_altered
+              && ! invariant_p (XEXP (loop_store_mems[0], 0)));
+
+         /* If the store depends on a register that is set after the
+            store, it depends on the initial value, and is thus not
+            reversible.  */
+         for (v = bl->giv; reversible_mem_store && v; v = v->next_iv)
+           {
+             if (v->giv_type == DEST_REG
+                 && reg_mentioned_p (v->dest_reg, loop_store_mems[0])
+                 && (INSN_UID (v->insn) >= max_uid_for_loop
+                     || (INSN_LUID (v->insn)
+                         > INSN_LUID (first_loop_store_insn))))
+               reversible_mem_store = 0;
+           }
+       }
 
       /* This code only acts for innermost loops.  Also it simplifies
         the memory address check by only reversing loops with