[PATCH] Fix another Alpha ICE in if_then_else_cond

[Jakub Jelinek]

Hi!

The following testcase was not fixed by
http://gcc.gnu.org/ml/gcc-patches/2001-12/msg02116.html.
The problem is that gen_lowpart_common fails on:
(ashiftrt:DI (ashift:DI (subreg:DI (div:SI ())))
and simplify_binary_operation failed.
The following patch fixes it.
Or do you prefer instead
	      /* On some platforms DIV uses narrower mode than its
		 operands.  */
              rtx x = gen_lowpart_common (mode, op0);

	      if (x)
		return x;
	      break;
?
Bootstrap pending.
Ok to commit (the patch or the above modification to it)?

2002-01-03  Jakub Jelinek  <jakub@redhat.com>

	* simplify-rtx.c (simplify_binary_operation) [DIV]: If
	gen_lowpart_common fails, use gen_lowpart_SUBREG.

	* gcc.c-torture/compile/20020103-1.c: New test.

--- gcc/testsuite/gcc.c-torture/compile/20020103-1.c.jj	Thu Jan  3 13:48:21 2002
+++ gcc/testsuite/gcc.c-torture/compile/20020103-1.c	Thu Jan  3 13:48:30 2002
@@ -0,0 +1,22 @@
+/* This testcase failed on Alpha at -O2 when simplifying conditional
+   expressions.  */
+
+int foo (void);
+
+struct A
+{
+  int a, b, c, d;
+};
+
+void bar (struct A *x)
+{
+  int e, f;
+
+  e = foo ();
+  e = e / x->b;
+  if (e < 1)
+    e = 1;
+  f = (x->a + x->c) / e;
+  if (f < x->d)
+    x->d -= (1 << 16) / 8;
+}
--- gcc/simplify-rtx.c.jj	Sat Dec 29 22:11:41 2001
+++ gcc/simplify-rtx.c	Thu Jan  3 13:46:55 2002
@@ -1413,8 +1413,15 @@ simplify_binary_operation (code, mode, o
 	case DIV:
 	  if (trueop1 == CONST1_RTX (mode))
 	    {
+	      /* On some platforms DIV uses narrower mode than its
+		 operands.  */
 	      rtx x = gen_lowpart_common (mode, op0);
-	      return x ? x : op0;
+	      if (x)
+		return x;
+	      else if (GET_MODE (op0) != VOIDmode)
+		return gen_lowpart_SUBREG (mode, op0);
+	      else
+		return op0;
 	    }
 
 	  /* In IEEE floating point, 0/x is not always 0.  */

	Jakub