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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/50955] [4.7 Regression] IVopts incorrectly rewrite the address of a global memory access into a local form. Date: Wed, 02 Nov 2011 13:10:00 -0000 [thread overview] Message-ID: <bug-50955-4-bppe7jDa0O@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-50955-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50955 --- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-11-02 13:09:40 UTC --- It looks like IVOPTs fails to consider a candidate for the use inquestion and thus, after choosing the final IV set ends up rewriting that use into this stupid form (instead of using candidate 0). The use is use 3 generic in statement vect_p.60_223 = PHI <vect_p.60_224(16), vect_p.63_222(5)> at position type vector(8) unsigned char * base batmp.61_221 + 1 step 8 base object (void *) batmp.61_221 is a biv related candidates but costs say: Use 3: cand cost compl. depends on 0 8 1 inv_expr:0 1 4 1 inv_expr:1 2 4 1 inv_expr:0 3 4 1 inv_expr:1 4 4 1 inv_expr:2 Initial set of candidates: cost: 24 (complexity 4) cand_cost: 10 cand_use_cost: 10 (complexity 4) candidates: 0, 4 use:0 --> iv_cand:4, cost=(2,1) use:1 --> iv_cand:4, cost=(2,1) use:2 --> iv_cand:4, cost=(2,1) use:3 --> iv_cand:4, cost=(4,1) use:4 --> iv_cand:0, cost=(0,0) invariants 7 Selected IV set: candidate 0 (important) var_before ivtmp.107_150 var_after ivtmp.107_256 incremented before exit test type unsigned int base 0 step 1 candidate 4 (important) var_before ivtmp.110_241 var_after ivtmp.110_146 incremented before exit test type unsigned int base (unsigned int) (&p1 + 8) step 8 base object (void *) &p1 so expressing use 3 with candidate 4 is cheaper than with candidate 0... Now, for address-uses we have if (address_p) { /* Do not try to express address of an object with computation based on address of a different object. This may cause problems in rtl level alias analysis (that does not expect this to be happening, as this is illegal in C), and would be unlikely to be useful anyway. */ if (use->iv->base_object && cand->iv->base_object && !operand_equal_p (use->iv->base_object, cand->iv->base_object, 0)) return infinite_cost; in cost calculation, but in this case it's a nonlinear use, and we have (gdb) call debug_generic_expr (use->iv->base_object) (void *) batmp.61_221 (gdb) call debug_generic_expr (cand->iv->base_object) (void *) &p1
next prev parent reply other threads:[~2011-11-02 13:10 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-11-02 5:12 [Bug tree-optimization/50955] New: " duyuehai at gmail dot com 2011-11-02 5:19 ` [Bug tree-optimization/50955] " duyuehai at gmail dot com 2011-11-02 9:42 ` [Bug tree-optimization/50955] [4.7 Regression] " rguenth at gcc dot gnu.org 2011-11-02 12:50 ` rguenth at gcc dot gnu.org 2011-11-02 13:10 ` rguenth at gcc dot gnu.org [this message] 2011-11-02 13:33 ` rguenth at gcc dot gnu.org 2011-11-03 6:25 ` duyuehai at gmail dot com 2011-11-03 7:52 ` rguenther at suse dot de 2011-11-03 8:07 ` rakdver at kam dot mff.cuni.cz 2011-11-03 8:19 ` rguenth at gcc dot gnu.org 2011-12-06 13:56 ` rguenth at gcc dot gnu.org 2012-01-31 10:51 ` rguenth at gcc dot gnu.org 2012-01-31 14:24 ` rguenth at gcc dot gnu.org 2012-02-06 13:43 ` rguenth at gcc dot gnu.org 2012-02-06 13:44 ` rguenth at gcc dot gnu.org 2013-08-16 4:19 ` pinskia at gcc dot gnu.org 2013-08-16 7:02 ` pinskia at gcc dot gnu.org 2013-08-28 8:33 ` rguenther at suse dot de 2013-12-18 9:42 ` rguenther at suse dot de 2013-12-18 10:24 ` amker.cheng at gmail dot com 2013-12-19 9:57 ` rguenth at gcc dot gnu.org 2015-08-28 9:16 ` amker at gcc dot gnu.org
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