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From: gbv@oxixares.com To: gcc-gnats@gcc.gnu.org Subject: c/5926: gcc 3.0.3 generates incorrect code with -O3 option Date: Tue, 12 Mar 2002 12:06:00 -0000 [thread overview] Message-ID: <200203122003.g2CK3Jf01400@mozart.oxixares.com> (raw) >Number: 5926 >Category: c >Synopsis: gcc 3.0.3 generates incorrect code with -O3 option >Confidential: no >Severity: non-critical >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Tue Mar 12 12:06:00 PST 2002 >Closed-Date: >Last-Modified: >Originator: Guillermo Ballester Valor >Release: 3.0.3 >Organization: >Environment: System: Linux mozart 2.2.19 #2 Sat Jun 2 21:32:31 CEST 2001 i586 unknown Architecture: i586 host: i586-pc-linux-gnu build: i586-pc-linux-gnu target: i586-pc-linux-gnu configured with: ./configure >Description: I've detected a problem when updated from gcc 2.95.2 . A result was different depending on the order of a line of code were written, without aparent cause, when using -O3 >How-To-Repeat: See the problem compiling the following code with -O3 option. The two routines are the same but a code of line changed. I think both results would be the same but I get different resuts. ----------------------------------- #include <stdio.h> #include <stdlib.h> #include <math.h> size_t last_nsize=0; #define BITS_PER_LIMB 32 unsigned long Y_MASQ,Y_LIMB,Y_MAX,Y_BITS; double Y_TINV; int bugy_routine(size_t n1, size_t n2) { size_t n,nsize,needed=0,i; nsize= n1 + n2; /*See whether all the initialization work con be avoided */ needed=(nsize*BITS_PER_LIMB); Y_BITS = (unsigned long)((double)24.00 - 0.5*log((double)needed)); Y_MASQ=((1U<<Y_BITS)-1L); Y_LIMB=(1U<<Y_BITS); Y_MAX=(1U<<(Y_BITS-1)); Y_TINV=1.0/(double)Y_LIMB; needed=(needed-1)/(size_t)Y_BITS+3; /****** LINE CHANGED *******/ return needed; } int nobugy_routine(size_t n1, size_t n2) { size_t n,nsize,needed=0,i; int save; nsize= n1 + n2; /*See whether all the initialization work con be avoided */ needed=(nsize*BITS_PER_LIMB); Y_BITS = (unsigned long)((double)24.00 - 0.5*log((double)needed)); needed=(needed-1)/(size_t)Y_BITS+3; /****** LINE CHANGED *******/ Y_MASQ=((1U<<Y_BITS)-1L); Y_LIMB=(1U<<Y_BITS); Y_MAX=(1U<<(Y_BITS-1)); Y_TINV=1.0/(double)Y_LIMB; return needed; } int main(int argc, char **argv) { size_t n1=500, n2=500, res1, res2; res1=nobugy_routine(n1,n2); printf("Results of no bugy routine %i\n",res1); res2=bugy_routine(n1,n2); printf("Results of bugy routine %i\n",res2); } ------------------------------------------ >Fix: I don't know >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-03-12 20:06 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-03-12 12:06 gbv [this message] 2002-03-18 15:47 jakub 2002-03-18 22:26 Guillermo Ballester Valor 2002-04-29 0:26 gbv 2003-01-01 19:08 neroden
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