From: Bernd Schmidt <bernds@redhat.co.uk>
Date: Thu, 30 Nov 2000 13:43:30 +0000 (+0000)
Subject: Backport two changes to the 2.95 branch
X-Git-Tag: prereleases/gcc-2.95.3-test1~42
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=71e2a3f193e6c4c0e98ebced1db482a04bbba335;p=thirdparty%2Fgcc.git

Backport two changes to the 2.95 branch

From-SVN: r37891
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1456bc36b982..96efcf396431 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 2000-11-30  Bernd Schmidt  <bernds@redhat.co.uk>
 
+	2000-09-01  Jim Wilson  <wilson@cygnus.com>
+	* loop.c (check_final_value): Check for biv use before checking for
+	giv use.  Check for both biv and giv uses.  Always set last_giv_use
+	if there is a giv use.
+
+	2000-09-29  Franz Sirl  <Franz.Sirl-kernel@lauterbach.com>
+	* loop.c (check_final_value): A GIV is not replaceable if used
+	before set.
+
 	Sun Oct 10 13:28:48 1999  Bernd Schmidt  <bernds@redhat.co.uk>
 	* loop.c (find_and_verify_loops): When looking for a BARRIER, don't
 	use one before a jump table.
diff --git a/gcc/loop.c b/gcc/loop.c
index 0b121cb918c5..3991a71fdb8b 100644
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -5692,6 +5692,7 @@ check_final_value (v, loop_start, loop_end, n_iterations)
         or all uses follow that insn in the same basic block),
      - its final value can be calculated (this condition is different
        than the one above in record_giv)
+     - it's not used before it's set
      - no assignments to the biv occur during the giv's lifetime.  */
 
 #if 0
@@ -5703,7 +5704,7 @@ check_final_value (v, loop_start, loop_end, n_iterations)
   if ((final_value = final_giv_value (v, loop_start, loop_end, n_iterations))
       && (v->always_computable || last_use_this_basic_block (v->dest_reg, v->insn)))
     {
-      int biv_increment_seen = 0;
+      int biv_increment_seen = 0, before_giv_insn = 0;
       rtx p = v->insn;
       rtx last_giv_use;
 
@@ -5733,26 +5734,35 @@ check_final_value (v, loop_start, loop_end, n_iterations)
 	{
 	  p = NEXT_INSN (p);
 	  if (p == loop_end)
-	    p = NEXT_INSN (loop_start);
+	    {
+	      before_giv_insn = 1;
+	      p = NEXT_INSN (loop_start);
+	    }
 	  if (p == v->insn)
 	    break;
 
 	  if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
 	      || GET_CODE (p) == CALL_INSN)
 	    {
-	      if (biv_increment_seen)
+	      /* It is possible for the BIV increment to use the GIV if we
+		 have a cycle.  Thus we must be sure to check each insn for
+		 both BIV and GIV uses, and we must check for BIV uses
+		 first.  */
+
+	      if (! biv_increment_seen
+		  && reg_set_p (v->src_reg, PATTERN (p)))
+		biv_increment_seen = 1;
+
+	      if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
 		{
-		  if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
+		  if (biv_increment_seen || before_giv_insn)
 		    {
 		      v->replaceable = 0;
 		      v->not_replaceable = 1;
 		      break;
 		    }
+		  last_giv_use = p;
 		}
-	      else if (reg_set_p (v->src_reg, PATTERN (p)))
-		biv_increment_seen = 1;
-	      else if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
-		last_giv_use = p;
 	    }
 	}