On Mon, 18 May 2015, Jakub Jelinek wrote:
> Hi!
>
> As the testcases show, for signed types we really should use SIGNED rather
> than UNSIGNED as tree_int_cst_min_precision argument, that function doesn't
> really do the desired thing with UNSIGNED for negative values and with
> -fwrapv we just want the narrowing cast to not lose anything from the
> number. Additionally, as for TYPE_OVERFLOW_WRAPS case we perform the +/-/& in
> unsigned type, we have to avoid all negative masks, because those surely
> have the higher bits set.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> For plus and unsigned type, we could improve it even further, as in that
> case we could just check if the bit immediately above precision is clear
> in the mask, higher bits than that are uninteresting, because the addition
> will have always zeros there. Perhaps as a follow-up?
> I mean say uchar foo (uchar a, uchar b) { return (x + y) & 0x72fe; }
> can be done as uchar addition & 0xfe, but not e.g. & 0x71fe.
>
> 2015-05-18 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/66187
> * match.pd ((bit_and (plus/minus (convert @0) (convert @1)) mask)):
> Pass TYPE_SIGN to tree_int_cst_min_precision. If
> !TYPE_OVERFLOW_WRAPS, ensure @4 is non-negative.
>
> * gcc.c-torture/execute/pr66187.c: New test.
> * gcc.dg/pr66187-1.c: New test.
> * gcc.dg/pr66187-2.c: New test.
>
> --- gcc/match.pd.jj 2015-05-18 09:46:39.000000000 +0200
> +++ gcc/match.pd 2015-05-18 10:20:24.944475737 +0200
> @@ -1115,8 +1115,10 @@ (define_operator_list CBRT BUILT_IN_CBRT
> /* The inner conversion must be a widening conversion. */
> && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (TREE_TYPE (@0))
> && types_match (@0, @1)
> - && (tree_int_cst_min_precision (@4, UNSIGNED)
> + && (tree_int_cst_min_precision (@4, TYPE_SIGN (TREE_TYPE (@0)))
> <= TYPE_PRECISION (TREE_TYPE (@0)))
> + && (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0))
> + || tree_int_cst_sgn (@4) >= 0)
> && single_use (@5))
> (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
> (with { tree ntype = TREE_TYPE (@0); }
> --- gcc/testsuite/gcc.c-torture/execute/pr66187.c.jj 2015-05-18
> 10:53:43.953654893 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/pr66187.c 2015-05-18
> 10:53:28.000000000 +0200
> @@ -0,0 +1,16 @@
> +/* PR tree-optimization/66187 */
> +
> +int a = 1, e = -1;
> +short b, f;
> +
> +int
> +main ()
> +{
> + f = e;
> + int g = b < 0 ? 0 : f + b;
> + if ((g & -4) < 0)
> + a = 0;
> + if (a)
> + __builtin_abort ();
> + return 0;
> +}
> --- gcc/testsuite/gcc.dg/pr66187-1.c.jj 2015-05-18 10:54:30.677906029
> +0200
> +++ gcc/testsuite/gcc.dg/pr66187-1.c 2015-05-18 12:30:17.000000000 +0200
> @@ -0,0 +1,97 @@
> +/* PR tree-optimization/66187 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-wrapv" } */
> +
> +__attribute__((noinline, noclone)) int
> +f0 (unsigned char x, unsigned char y)
> +{
> + return (x + y) & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f1 (unsigned char x, unsigned char y)
> +{
> + return (x - y) & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f2 (signed char x, signed char y)
> +{
> + return (x + y) & -4;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f3 (signed char x, signed char y)
> +{
> + return (x + y) & 0xf8;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f4 (signed char x, signed char y)
> +{
> + return (x + y) & 0x78;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f5 (unsigned char x, unsigned char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f6 (unsigned char x, unsigned char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a - b;
> + return c & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f7 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & -4;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f8 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0xf8;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f9 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0x78;
> +}
> +
> +int
> +main ()
> +{
> + if (__SCHAR_MAX__ != 127 || sizeof (int) != 4)
> + return 0;
> + if (f0 (0xff, 0xff) != 0xfe
> + || f1 (0, 1) != 0x2ff
> + || f2 (-2, 1) != -4
> + || f3 (-2, 1) != 0xf8
> + || f4 (-2, 1) != 0x78
> + || f5 (0xff, 0xff) != 0xfe
> + || f6 (0, 1) != 0x2ff
> + || f7 (-2, 1) != -4
> + || f8 (-2, 1) != 0xf8
> + || f9 (-2, 1) != 0x78)
> + __builtin_abort ();
> + return 0;
> +}
> --- gcc/testsuite/gcc.dg/pr66187-2.c.jj 2015-05-18 12:31:39.398176973
> +0200
> +++ gcc/testsuite/gcc.dg/pr66187-2.c 2015-05-18 12:31:46.319067151 +0200
> @@ -0,0 +1,97 @@
> +/* PR tree-optimization/66187 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fwrapv" } */
> +
> +__attribute__((noinline, noclone)) int
> +f0 (unsigned char x, unsigned char y)
> +{
> + return (x + y) & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f1 (unsigned char x, unsigned char y)
> +{
> + return (x - y) & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f2 (signed char x, signed char y)
> +{
> + return (x + y) & -4;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f3 (signed char x, signed char y)
> +{
> + return (x + y) & 0xf8;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f4 (signed char x, signed char y)
> +{
> + return (x + y) & 0x78;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f5 (unsigned char x, unsigned char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f6 (unsigned char x, unsigned char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a - b;
> + return c & 0x2ff;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f7 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & -4;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f8 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0xf8;
> +}
> +
> +__attribute__((noinline, noclone)) int
> +f9 (signed char x, signed char y)
> +{
> + int a = x;
> + int b = y;
> + int c = a + b;
> + return c & 0x78;
> +}
> +
> +int
> +main ()
> +{
> + if (__SCHAR_MAX__ != 127 || sizeof (int) != 4)
> + return 0;
> + if (f0 (0xff, 0xff) != 0xfe
> + || f1 (0, 1) != 0x2ff
> + || f2 (-2, 1) != -4
> + || f3 (-2, 1) != 0xf8
> + || f4 (-2, 1) != 0x78
> + || f5 (0xff, 0xff) != 0xfe
> + || f6 (0, 1) != 0x2ff
> + || f7 (-2, 1) != -4
> + || f8 (-2, 1) != 0xf8
> + || f9 (-2, 1) != 0x78)
> + __builtin_abort ();
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham
Norton, HRB 21284 (AG Nuernberg)
