Hi!
The op1 - op2 line instead of multiplication is something that has been
introduced in C++ double_int changes, but without the 2 * TYPE_PRECISION
prec it would always return 0 or -1 anyway. And, with wide_mul_with_sign
we can also handle 2 * HOST_BITS_PER_WIDE_INT precisions.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.8?
2013-04-11 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/56918
PR tree-optimization/56920
* fold-const.c (int_const_binop_1): Use op1.mul_with_sign (op2, ...)
instead of op1 - op2. Pass 2 * TYPE_PRECISION (type) as second
argument to rshift method. For 2 * HOST_BITS_PER_WIDE_INT precision
use wide_mul_with_sign method.
* gcc.dg/vect/pr56918.c: New test.
* gcc.dg/vect/pr56920.c: New test.
--- gcc/fold-const.c.jj 2013-04-11 09:36:41.000000000 +0200
+++ gcc/fold-const.c 2013-04-11 16:16:50.273545925 +0200
@@ -984,12 +984,16 @@ int_const_binop_1 (enum tree_code code,
break;
case MULT_HIGHPART_EXPR:
- /* ??? Need quad precision, or an additional shift operand
- to the multiply primitive, to handle very large highparts. */
if (TYPE_PRECISION (type) > HOST_BITS_PER_WIDE_INT)
- return NULL_TREE;
- tmp = op1 - op2;
- res = tmp.rshift (TYPE_PRECISION (type), TYPE_PRECISION (type), !uns);
+ {
+ if (TYPE_PRECISION (type) != 2 * HOST_BITS_PER_WIDE_INT)
+ return NULL_TREE;
+ op1.wide_mul_with_sign (op2, false, &res, &overflow);
+ break;
+ }
+ tmp = op1.mul_with_sign (op2, false, &overflow);
+ res
+ = tmp.rshift (TYPE_PRECISION (type), 2 * TYPE_PRECISION (type), !uns);
break;
case TRUNC_DIV_EXPR:
--- gcc/testsuite/gcc.dg/vect/pr56918.c.jj 2013-04-11 16:26:36.269168125
+0200
+++ gcc/testsuite/gcc.dg/vect/pr56918.c 2013-04-11 16:30:07.410945804 +0200
@@ -0,0 +1,31 @@
+/* PR tree-optimization/56918 */
+/* { dg-additional-options "-O3" } */
+
+#include "tree-vect.h"
+
+extern void abort (void);
+double data[8];
+
+__attribute__((noinline, noclone)) void
+foo ()
+{
+ int i;
+ for (i = 0; i < 8; ++i)
+ data[i] = ((i + 2) % 3) + 1;
+}
+
+int
+main ()
+{
+ int i;
+ check_vect ();
+ foo ();
+ if (data[0] != 3 || data[7] != 1)
+ abort ();
+ for (i = 1; i < 4; ++i)
+ if (data[i] != i || data[i + 3] != i)
+ abort ();
+ return 0;
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */
--- gcc/testsuite/gcc.dg/vect/pr56920.c.jj 2013-04-11 17:16:48.570982675
+0200
+++ gcc/testsuite/gcc.dg/vect/pr56920.c 2013-04-11 17:17:28.310757853 +0200
@@ -0,0 +1,21 @@
+/* PR tree-optimization/56920 */
+/* { dg-additional-options "-O3" } */
+
+#include "tree-vect.h"
+
+extern void abort (void);
+
+int
+main ()
+{
+ unsigned int a[15], i;
+ check_vect ();
+ for (i = 0; i < 15; ++i)
+ a[i] = (i * 2) % 15;
+ for (i = 0; i < 15; ++i)
+ if (a[i] != (i * 2) % 15)
+ abort ();
+ return 0;
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */
Jakub
