[PATCH] Fix (neg (lt X 0)) optimization (PR rtl-optimization/33148)

[Jakub Jelinek]

Hi!

PR25600 change introduced an optimization of (neg (lt x 0)) to
(ashirtrt x C), but it is not checking whether x's mode is suitable
for it.  As it checks that op1 is const0_rtx, I believe MODE_FLOAT
or VECTOR_MODE_P modes are not a problem, CC modes can certainly appear
in LT's first operand with second operand const0_rtx.
So, when we optimize
(neg:DI (lt:DI (reg:CC ...) (const_int 0)))
we create something like
(sign_extend:DI (ashirtrt:CC (reg:CC ...) (const_int 31)))
which is IMHO invalid RTL, ashirtrt is documented on fixed point modes
only (guess vector modes aren't listed just by omission) and so is
sign_extend.

Ok for 4.2/trunk?

2007-08-27  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/33148
	* simplify-rtx.c (simplify_unary_operation_1): Only optimize
	(neg (lt X 0)) if X has scalar int mode.

	* gcc.c-torture/compile/20070827-1.c: New test.

--- gcc/simplify-rtx.c.jj	2007-08-27 10:15:33.000000000 +0200
+++ gcc/simplify-rtx.c	2007-08-27 12:12:51.000000000 +0200
@@ -583,7 +583,8 @@ simplify_unary_operation_1 (enum rtx_cod
       /* (neg (lt x 0)) is (ashiftrt X C) if STORE_FLAG_VALUE is 1.  */
       /* (neg (lt x 0)) is (lshiftrt X C) if STORE_FLAG_VALUE is -1.  */
       if (GET_CODE (op) == LT
-	  && XEXP (op, 1) == const0_rtx)
+	  && XEXP (op, 1) == const0_rtx
+	  && SCALAR_INT_MODE_P (GET_MODE (XEXP (op, 0))))
 	{
 	  enum machine_mode inner = GET_MODE (XEXP (op, 0));
 	  int isize = GET_MODE_BITSIZE (inner);
--- gcc/testsuite/gcc.c-torture/compile/20070827-1.c.jj	2007-08-27 12:17:20.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/20070827-1.c	2007-08-27 12:15:45.000000000 +0200
@@ -0,0 +1,20 @@
+/* PR rtl-optimization/33148 */
+
+int
+foo (unsigned int *p, int *q, unsigned int w, unsigned int b)
+{
+  unsigned int i;
+  int mask;
+
+  if (q[0] < q[1])
+    mask = 0xff;
+  else
+    mask = 0;
+
+  for (i = 0; 8 * i < w; i++)
+    {
+      b ^= mask;
+      *p++ = b;
+    }
+  return 0;
+}

	Jakub