* combine.c (unmentioned_reg_p): New function to check whether an

	expression is a "specialization" of another, i.e. that there are
	no registers or memory references mentioned in the first that don't
	appear in the second.
	(unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
	(combine_instructions): Also try combining instructions using the
	REG_EQUAL note from a preceding log-linked instruction.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@79398 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index ca4525c..70c720c 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,15 @@
 2004-03-12  Roger Sayle  <roger@eyesopen.com>
 
+       * combine.c (unmentioned_reg_p): New function to check whether an
+       expression is a "specialization" of another, i.e. that there are
+       no registers or memory references mentioned in the first that don't
+       appear in the second.
+       (unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
+       (combine_instructions): Also try combining instructions using the
+       REG_EQUAL note from a preceding log-linked instruction.
+
+2004-03-12  Roger Sayle  <roger@eyesopen.com>
+
        * config/i386/i386.c (ix86_split_ashrdi): Optimize shift by 63.
 
 2004-03-12  Matt Austern  <austern@apple.com>

diff --git a/gcc/combine.c b/gcc/combine.c
index c627187..a32e479 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -407,6 +407,8 @@ static int insn_cuid (rtx);
 static void record_promoted_value (rtx, rtx);
 static rtx reversed_comparison (rtx, enum machine_mode, rtx, rtx);
 static enum rtx_code combine_reversed_comparison_code (rtx);
+static int unmentioned_reg_p_1 (rtx *, void *);
+static bool unmentioned_reg_p (rtx, rtx);
 \f
 /* Substitute NEWVAL, an rtx expression, into INTO, a place in some
    insn.  The substitution can be undone by undo_all.  If INTO is already
@@ -720,6 +722,31 @@ combine_instructions (rtx f, unsigned int nregs)
                                           &new_direct_jump_p)) != 0)
                    goto retry;
 
+             /* Try this insn with each REG_EQUAL note it links back to.  */
+             for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
+               {
+                 rtx set, note;
+                 rtx temp = XEXP (links, 0);
+                 if ((set = single_set (temp)) != 0
+                     && (note = find_reg_equal_equiv_note (temp)) != 0
+                     && GET_CODE (XEXP (note, 0)) != EXPR_LIST
+                     /* Avoid using a register that may already been marked
+                        dead by an earlier instruction.  */
+                     && ! unmentioned_reg_p (XEXP (note, 0), SET_SRC (set)))
+                   {
+                     /* Temporarily replace the set's source with the
+                        contents of the REG_EQUAL note.  The insn will
+                        be deleted or recognized by try_combine.  */
+                     rtx orig = SET_SRC (set);
+                     SET_SRC (set) = XEXP (note, 0);
+                     next = try_combine (insn, temp, NULL_RTX,
+                                         &new_direct_jump_p);
+                     if (next)
+                       goto retry;
+                     SET_SRC (set) = orig;
+                   }
+               }
+
              if (GET_CODE (insn) != NOTE)
                record_dead_and_set_regs (insn);
 
@@ -12979,6 +13006,33 @@ distribute_links (rtx links)
     }
 }
 \f
+/* Subroutine of unmentioned_reg_p and callback from for_each_rtx.
+   Check whether the expression pointer to by LOC is a register or
+   memory, and if so return 1 if it isn't mentioned in the rtx EXPR.
+   Otherwise return zero.  */
+
+static int
+unmentioned_reg_p_1 (rtx *loc, void *expr)
+{
+  rtx x = *loc;
+
+  if (x != NULL_RTX
+      && (GET_CODE (x) == REG || GET_CODE (x) == MEM)
+      && ! reg_mentioned_p (x, (rtx) expr))
+    return 1;
+  return 0;
+}
+
+/* Check for any register or memory mentioned in EQUIV that is not
+   mentioned in EXPR.  This is used to restrict EQUIV to "specializations"
+   of EXPR where some registers may have been replaced by constants.  */
+
+static bool
+unmentioned_reg_p (rtx equiv, rtx expr)
+{
+  return for_each_rtx (&equiv, unmentioned_reg_p_1, expr);
+}
+\f
 /* Compute INSN_CUID for INSN, which is an insn made by combine.  */
 
 static int