From: Bernd Schmidt <bernds@redhat.co.uk>
Date: Thu, 30 Nov 2000 14:16:55 +0000 (+0000)
Subject: Backport a change to the 2.95 branch
X-Git-Tag: prereleases/gcc-2.95.3-test1~41
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a8c23b3a9e263627b52d7b9d6d7aa5c1eb049195;p=thirdparty%2Fgcc.git

Backport a change to the 2.95 branch

From-SVN: r37892
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 96efcf396431..2e140caed00c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 2000-11-30  Bernd Schmidt  <bernds@redhat.co.uk>
 
+	Based on a patch from Geoff Keating <geoffk@redhat.com>:
+	* loop.c (basic_induction_var): If a REG is set from something
+	that is not a biv, then the REG is not a biv.  Even if it is
+	earlier set from something that is a biv.
+
 	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
diff --git a/gcc/loop.c b/gcc/loop.c
index 3991a71fdb8b..1aa56b75029a 100644
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -6007,6 +6007,7 @@ basic_induction_var (x, mode, dest_reg, p, inc_val, mult_val, location)
       insn = p;
       while (1)
 	{
+	  rtx dest;
 	  do {
 	    insn = PREV_INSN (insn);
 	  } while (insn && GET_CODE (insn) == NOTE
@@ -6018,20 +6019,26 @@ basic_induction_var (x, mode, dest_reg, p, inc_val, mult_val, location)
 	  if (set == 0)
 	    break;
 
-	  if ((SET_DEST (set) == x
-	       || (GET_CODE (SET_DEST (set)) == SUBREG
-		   && (GET_MODE_SIZE (GET_MODE (SET_DEST (set)))
-		       <= UNITS_PER_WORD)
-		   && (GET_MODE_CLASS (GET_MODE (SET_DEST (set)))
-		       == MODE_INT)
-		   && SUBREG_REG (SET_DEST (set)) == x))
-	      && basic_induction_var (SET_SRC (set),
-				      (GET_MODE (SET_SRC (set)) == VOIDmode
-				       ? GET_MODE (x)
-				       : GET_MODE (SET_SRC (set))),
-				      dest_reg, insn,
-				      inc_val, mult_val, location))
-	    return 1;
+	  dest = SET_DEST (set);
+	  if (dest == x
+	      || (GET_CODE (dest) == SUBREG
+		  && (GET_MODE_SIZE (GET_MODE (dest)) <= UNITS_PER_WORD)
+		  && (GET_MODE_CLASS (GET_MODE (dest)) == MODE_INT)
+		  && SUBREG_REG (dest) == x))
+	    return basic_induction_var (SET_SRC (set),
+					(GET_MODE (SET_SRC (set)) == VOIDmode
+					 ? GET_MODE (x)
+					 : GET_MODE (SET_SRC (set))),
+					dest_reg, insn,
+					inc_val, mult_val, location);
+
+	  while (GET_CODE (dest) == SIGN_EXTRACT
+		 || GET_CODE (dest) == ZERO_EXTRACT
+		 || GET_CODE (dest) == SUBREG
+		 || GET_CODE (dest) == STRICT_LOW_PART)
+	    dest = XEXP (dest, 0);
+	  if (dest == x)
+	    break;
 	}
       /* ... fall through ...  */