* ifcvt.c (noce_get_alt_condition): Use prev_nonnote_insn.

	(noce_try_abs): Negate if the comparison is reversed.
	Look only one instruction backwards for a REG_EQUAL note.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@106706 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 22 insertions, 15 deletions

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index da32ab45a71..e7eec87bfc1 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -1485,7 +1485,7 @@ noce_get_alt_condition (struct noce_if_info *if_info, rtx target,
       rtx prev_insn;
 
       /* First, look to see if we put a constant in a register.  */
-      prev_insn = PREV_INSN (if_info->cond_earliest);
+      prev_insn = prev_nonnote_insn (if_info->cond_earliest);
       if (prev_insn
 	  && INSN_P (prev_insn)
 	  && GET_CODE (PATTERN (prev_insn)) == SET)
@@ -1697,7 +1697,9 @@ noce_try_abs (struct noce_if_info *if_info)
   if (no_new_pseudos)
     return FALSE;
 
-  /* Recognize A and B as constituting an ABS or NABS.  */
+  /* Recognize A and B as constituting an ABS or NABS.  The canonical
+     form is a branch around the negation, taken when the object is the
+     first operand of a comparison against 0 that evaluates to true.  */
   a = if_info->a;
   b = if_info->b;
   if (GET_CODE (a) == NEG && rtx_equal_p (XEXP (a, 0), b))
@@ -1718,25 +1720,30 @@ noce_try_abs (struct noce_if_info *if_info)
   if (rtx_equal_p (XEXP (cond, 0), b))
     c = XEXP (cond, 1);
   else if (rtx_equal_p (XEXP (cond, 1), b))
-    c = XEXP (cond, 0);
+    {
+      c = XEXP (cond, 0);
+      negate = !negate;
+    }
   else
     return FALSE;
 
-  /* Verify that C is zero.  Search backward through the block for
-     a REG_EQUAL note if necessary.  */
+  /* Verify that C is zero.  Search one step backward for a
+     REG_EQUAL note or a simple source if necessary.  */
   if (REG_P (c))
     {
-      rtx insn, note = NULL;
-      for (insn = earliest;
-	   insn != BB_HEAD (if_info->test_bb);
-	   insn = PREV_INSN (insn))
-	if (INSN_P (insn)
-	    && ((note = find_reg_note (insn, REG_EQUAL, c))
-		|| (note = find_reg_note (insn, REG_EQUIV, c))))
-	  break;
-      if (! note)
+      rtx set, insn = prev_nonnote_insn (earliest);
+      if (insn
+	  && (set = single_set (insn))
+	  && rtx_equal_p (SET_DEST (set), c))
+	{
+	  rtx note = find_reg_equal_equiv_note (insn);
+	  if (note)
+	    c = XEXP (note, 0);
+	  else
+	    c = SET_SRC (set);
+	}
+      else
 	return FALSE;
-      c = XEXP (note, 0);
     }
   if (MEM_P (c)
       && GET_CODE (XEXP (c, 0)) == SYMBOL_REF