* reload1.c (delete_output_reload): Ignore single USE that

	was emitted for the pseudo use of this INSN.
	If the no reference to REG between OUTPUT_RELOAD_INSN and INSN
	remains, we can always delete OUTPUT_RELOAD_INSN.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@19762 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bbbbc8f..fce1cc5 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+Fri May 15 05:35:37 1998  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+       * reload1.c (delete_output_reload): Ignore single USE that
+       was emitted for the pseudo use of this INSN.
+       If the no reference to REG between OUTPUT_RELOAD_INSN and INSN
+       remains, we can always delete OUTPUT_RELOAD_INSN.
+
 Thu May 14 18:38:50 1998  Jim Wilson  <wilson@cygnus.com>
 
        * reload.c (find_reloads): Don't penalize SCRATCH output reload.

diff --git a/gcc/reload1.c b/gcc/reload1.c
index f6d9a0f..1b4e8e4 100644 (file)
--- a/gcc/reload1.c
+++ b/gcc/reload1.c
@@ -7401,20 +7401,40 @@ delete_output_reload (insn, j, output_reload_insn)
        return;
       if ((GET_CODE (i1) == INSN || GET_CODE (i1) == CALL_INSN)
          && reg_mentioned_p (reg, PATTERN (i1)))
-       return;
+       {
+         /* If this is just a single USE with an REG_EQUAL note in front
+            of INSN, this is no problem, because this mentions just the
+            address that we are using here.
+            But if there is more than one such USE, the insn might use
+            the operand directly, or another reload might do that.
+            This is analogous to the count_occurences check in the callers.  */
+         int num_occurences = 0;
+
+         while (GET_CODE (i1) == INSN && GET_CODE (PATTERN (i1)) == USE
+                && find_reg_note (i1, REG_EQUAL, NULL_RTX))
+           {
+             num_occurences += rtx_equal_p (reg, XEXP (PATTERN (i1), 0)) != 0;
+             i1 = NEXT_INSN (i1);
+           }
+         if (num_occurences == 1 && i1 == insn)
+           break;
+         return;
+       }
     }
 
-  /* If this insn will store in the pseudo again,
-     the previous store can be removed.  */
-  if (reload_out[j] == reload_in[j])
-    delete_insn (output_reload_insn);
-
-  /* See if the pseudo reg has been completely replaced
+  /* The caller has already checked that REG dies or is set in INSN.
+     It has also checked that we are optimizing, and thus some inaccurancies
+     in the debugging information are acceptable.
+     So we could just delete output_reload_insn.
+     But in some cases we can improve the debugging information without
+     sacrificing optimization - maybe even improving the code:
+     See if the pseudo reg has been completely replaced
      with reload regs.  If so, delete the store insn
      and forget we had a stack slot for the pseudo.  */
-  else if (REG_N_DEATHS (REGNO (reg)) == 1
-          && REG_BASIC_BLOCK (REGNO (reg)) >= 0
-          && find_regno_note (insn, REG_DEAD, REGNO (reg)))
+  if (reload_out[j] != reload_in[j]
+      && REG_N_DEATHS (REGNO (reg)) == 1
+      && REG_BASIC_BLOCK (REGNO (reg)) >= 0
+      && find_regno_note (insn, REG_DEAD, REGNO (reg)))
     {
       rtx i2;
 
@@ -7436,9 +7456,12 @@ delete_output_reload (insn, j, output_reload_insn)
            break;
          if ((GET_CODE (i2) == INSN || GET_CODE (i2) == CALL_INSN)
              && reg_mentioned_p (reg, PATTERN (i2)))
-           /* Some other ref remains;
-              we can't do anything.  */
-           return;
+           {
+             /* Some other ref remains; just delete the output reload we
+                know to be dead.  */
+             delete_insn (output_reload_insn);
+             return;
+           }
        }
 
       /* Delete the now-dead stores into this pseudo.  */
@@ -7464,6 +7487,8 @@ delete_output_reload (insn, j, output_reload_insn)
       reg_renumber[REGNO (reg)] = REGNO (reload_reg_rtx[j]);
       alter_reg (REGNO (reg), -1);
     }
+  delete_insn (output_reload_insn);
+
 }
 \f
 /* Output reload-insns to reload VALUE into RELOADREG.