ifcvt.c (noce_get_alt_condition): Use prev_nonnote_insn.

	* 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.

From-SVN: r106706

gcc/ChangeLog

+2005-11-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* 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.
+
 2005-11-09  Alexandre Oliva  <aoliva@redhat.com>
 
 	PR other/4372

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);
+      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)
-	return FALSE;
+      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;
     }
   if (MEM_P (c)
       && GET_CODE (XEXP (c, 0)) == SYMBOL_REF

gcc/testsuite/ChangeLog

+2005-11-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.dg/ifcvt-fabs-1.c: New test.
+
 2005-11-09  Alexandre Oliva  <aoliva@redhat.com>
 
 	PR other/4372

gcc/testsuite/gcc.dg/ifcvt-fabs-1.c

+/* { dg-do run } */
+/* { dg-options "-O" } */
+/* { dg-options "-O -march=i686" { target i686-*-* } } */
+
+extern void abort(void);
+
+float foo(float f)
+{
+  if (f < 0.0f)
+    f = -f;
+
+  return f;
+}
+
+int main(void)
+{
+  if (foo (-1.0f) != 1.0f)
+    abort ();
+
+  return 0;
+}