| Message ID | 20151209223703.GW5675@tucnak.redhat.com |
|---|---|
| State | New |
| Headers | show |
On 12/09/2015 11:37 PM, Jakub Jelinek wrote: > Not sure what I've been thinking when writing the previous noce_try_abs fix. > I thought that the optimization can be applied for all the conditions, > and whether it can be applied depends on if it is cond ? ~x : x or > cond ? x : ~x. But that is not the case, the optimization can be only > applied to a subset of conditions, and when it can be applied, it can be > applied to both the cond ? ~x : x and cond ? x : ~x cases (depending on > the condition one is one_cmpl_abs (x) and the other ~one_cmpl_abs (x)). Odd, I thought you made a good argument last time :-( Sorry for not catching the problem. > switch (GET_CODE (cond)) > { > - case GT: > - if (!negate) > - return FALSE; > - break; > case GE: > - /* >= 0 is the same case as above > -1. */ > - if (negate) > - return FALSE; > - break; > case LT: > - if (negate) > - return FALSE; > - break; > - case LE: > - /* <= 0 is the same case as above < 1. */ > - if (!negate) > - return FALSE; > break; > default: > return FALSE; This turns into a much simpler if statement, doesn't it? Ok with that change. > +/* PR rtl-optimization/68670 */ > +/* { dg-do run } */ > +/* { dg-options "-O2 -ftracer" } */ Curious what effect -ftracer has here? Bernd
On Thu, Dec 10, 2015 at 02:20:04PM +0100, Bernd Schmidt wrote: > This turns into a much simpler if statement, doesn't it? Ok with that > change. Ok, will do, thanks. > >+/* PR rtl-optimization/68670 */ > >+/* { dg-do run } */ > >+/* { dg-options "-O2 -ftracer" } */ > > Curious what effect -ftracer has here? In one case it was seeing all test_bb/then_bb/else_bb/join_bb, where one of then_bb/else_bb (don't remember which one) contained y = ~x and another one y = x, while the other case had no else_bb, with already test_bb doing y = x and then_bb then doing y = ~y. Correspondingly different condition, different negate value. Jakub
--- gcc/ifcvt.c.jj 2015-12-03 16:39:36.000000000 +0100 +++ gcc/ifcvt.c 2015-12-09 17:18:35.418052077 +0100 @@ -2601,17 +2601,14 @@ noce_try_abs (struct noce_if_info *if_in Note that these rtx constants are known to be CONST_INT, and therefore imply integer comparisons. The one_cmpl case is more complicated, as we want to handle - only x < 0 ? ~x : x or x >= 0 ? ~x : x but not - x <= 0 ? ~x : x or x > 0 ? ~x : x, as the latter two - have different result for x == 0. */ + only x < 0 ? ~x : x or x >= 0 ? x : ~x to one_cmpl_abs (x) + and x < 0 ? x : ~x or x >= 0 ? ~x : x to ~one_cmpl_abs (x), + but not other cases (x > -1 is equivalent of x >= 0). */ if (c == constm1_rtx && GET_CODE (cond) == GT) - { - if (one_cmpl && negate) - return FALSE; - } + ; else if (c == const1_rtx && GET_CODE (cond) == LT) { - if (one_cmpl && !negate) + if (one_cmpl) return FALSE; } else if (c == CONST0_RTX (GET_MODE (b))) @@ -2619,23 +2616,8 @@ noce_try_abs (struct noce_if_info *if_in if (one_cmpl) switch (GET_CODE (cond)) { - case GT: - if (!negate) - return FALSE; - break; case GE: - /* >= 0 is the same case as above > -1. */ - if (negate) - return FALSE; - break; case LT: - if (negate) - return FALSE; - break; - case LE: - /* <= 0 is the same case as above < 1. */ - if (!negate) - return FALSE; break; default: return FALSE; --- gcc/testsuite/gcc.c-torture/execute/pr68376-2.c.jj 2015-11-19 09:48:05.000000000 +0100 +++ gcc/testsuite/gcc.c-torture/execute/pr68376-2.c 2015-12-09 17:58:57.000000000 +0100 @@ -26,6 +26,30 @@ f4 (int x) return x <= 0 ? x : ~x; } +__attribute__((noinline, noclone)) int +f5 (int x) +{ + return x >= 0 ? ~x : x; +} + +__attribute__((noinline, noclone)) int +f6 (int x) +{ + return x >= 0 ? x : ~x; +} + +__attribute__((noinline, noclone)) int +f7 (int x) +{ + return x > 0 ? ~x : x; +} + +__attribute__((noinline, noclone)) int +f8 (int x) +{ + return x > 0 ? x : ~x; +} + int main () { @@ -37,5 +61,13 @@ main () abort (); if (f4 (5) != -6 || f4 (-5) != -5 || f4 (0) != 0) abort (); + if (f5 (5) != -6 || f5 (-5) != -5 || f5 (0) != -1) + abort (); + if (f6 (5) != 5 || f6 (-5) != 4 || f6 (0) != 0) + abort (); + if (f7 (5) != -6 || f7 (-5) != -5 || f7 (0) != 0) + abort (); + if (f8 (5) != 5 || f8 (-5) != 4 || f8 (0) != -1) + abort (); return 0; } --- gcc/testsuite/gcc.dg/pr68670-1.c.jj 2015-12-09 17:22:41.465621589 +0100 +++ gcc/testsuite/gcc.dg/pr68670-1.c 2015-12-09 17:22:05.251126555 +0100 @@ -0,0 +1,5 @@ +/* PR rtl-optimization/68670 */ +/* { dg-do run } */ +/* { dg-options "-O2 -ftracer" } */ + +#include "../gcc.c-torture/execute/pr68376-1.c" --- gcc/testsuite/gcc.dg/pr68670-2.c.jj 2015-12-09 17:22:44.528578868 +0100 +++ gcc/testsuite/gcc.dg/pr68670-2.c 2015-12-09 17:22:31.641758606 +0100 @@ -0,0 +1,5 @@ +/* PR rtl-optimization/68670 */ +/* { dg-do run } */ +/* { dg-options "-O2 -ftracer" } */ + +#include "../gcc.c-torture/execute/pr68376-2.c"