[PATCH] Fix ICE during combine (PR rtl-optimization/49619)

[PATCH] Fix ICE during combine (PR rtl-optimization/49619)

[Jakub Jelinek]

Hi!

The following testcase ICEs, because simplify_gen_binary (IOR, HImode, ...)
simplifies into (subreg:HI (reg:SI ...) 0), but was still passing
mode (HImode) as second argument to recursive combine_simplify_rtx call.
The second argument is op0_mode, so is supposed to be the real
mode which should be assumed for its first operand.
Passing mode in that case is only safe if simplify_gen_binary doesn't
actually simplify it, but as simplify_gen_binary would simplify constant
arguments anyway into a constant, it doesn't make any sense to hint
combine_simplify_rtx about the original op0_mode.  That is something
only useful when called from subst, which simplifies the operands (which may
turn them from non-VOIDmode into VOIDmode) and then calls
combine_simplify_rtx to simplify the whole operation.

The second part of the patch attempts to optimize more, as
simplify_gen_binary may already simplify the expression, so often (including
the testcase) combine_simplify_rtx doesn't simplify anything, i.e.
tor == temp, yet it is simplified over (ior plus_arg0 plus_arg1).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
For 4.6, I think safer would be just the first one liner change to pass
VOIDmode to combine_simplify_rtx.  Is that ok for 4.6?

2011-07-04  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/49619
	* combine.c (combine_simplify_rtx): In PLUS -> IOR simplification
	pass VOIDmode as op0_mode to recursive call, and return temp even
	when different from tor, just if it is not IOR of the original
	PLUS arguments.

	* gcc.dg/pr49619.c: New test.

--- gcc/combine.c.jj	2011-06-21 16:46:01.000000000 +0200
+++ gcc/combine.c	2011-07-04 16:05:52.000000000 +0200
@@ -5681,12 +5681,17 @@ combine_simplify_rtx (rtx x, enum machin
 	{
 	  /* Try to simplify the expression further.  */
 	  rtx tor = simplify_gen_binary (IOR, mode, XEXP (x, 0), XEXP (x, 1));
-	  temp = combine_simplify_rtx (tor, mode, in_dest, 0);
+	  temp = combine_simplify_rtx (tor, VOIDmode, in_dest, 0);
 
 	  /* If we could, great.  If not, do not go ahead with the IOR
 	     replacement, since PLUS appears in many special purpose
 	     address arithmetic instructions.  */
-	  if (GET_CODE (temp) != CLOBBER && temp != tor)
+	  if (GET_CODE (temp) != CLOBBER
+	      && (GET_CODE (temp) != IOR
+		  || ((XEXP (temp, 0) != XEXP (x, 0)
+		       || XEXP (temp, 1) != XEXP (x, 1))
+		      && (XEXP (temp, 0) != XEXP (x, 1)
+			  || XEXP (temp, 1) != XEXP (x, 0)))))
 	    return temp;
 	}
       break;
--- gcc/testsuite/gcc.dg/pr49619.c.jj	2011-07-04 16:04:21.000000000 +0200
+++ gcc/testsuite/gcc.dg/pr49619.c	2011-07-04 16:04:06.000000000 +0200
@@ -0,0 +1,13 @@
+/* PR rtl-optimization/49619 */
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-fre" } */
+
+extern int a, b;
+
+void
+foo (int x)
+{
+  a = 2;
+  b = 0;
+  b = (a && ((a = 1, 0 >= b) || (short) (x + (b & x))));
+}

	Jakub

Re: [PATCH] Fix ICE during combine (PR rtl-optimization/49619)

[Eric Botcazou]

> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> For 4.6, I think safer would be just the first one liner change to pass
> VOIDmode to combine_simplify_rtx.  Is that ok for 4.6?
>
> 2011-07-04  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR rtl-optimization/49619
> 	* combine.c (combine_simplify_rtx): In PLUS -> IOR simplification
> 	pass VOIDmode as op0_mode to recursive call, and return temp even
> 	when different from tor, just if it is not IOR of the original
> 	PLUS arguments.
>
> 	* gcc.dg/pr49619.c: New test.

OK for mainline, and for 4.6/4.5 branch as far as the first part is concerned.

-- 
Eric Botcazou