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From: gumo@lucifer.kgt.bme.hu To: gcc-gnats@gcc.gnu.org Subject: optimization/10620: for(i=25000;i;i--) {} generates wrong assembly source in avr-gcc with -O2 Date: Sun, 04 May 2003 14:26:00 -0000 [thread overview] Message-ID: <20030504142228.16846.qmail@sources.redhat.com> (raw) [-- Warning: decoded text below may be mangled, UTF-8 assumed --] [-- Attachment #1: Type: text/plain, Size: 1083 bytes --] >Number: 10620 >Category: optimization >Synopsis: for(i=25000;i;i--) {} generates wrong assembly source in avr-gcc with -O2 >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Sun May 04 14:26:01 UTC 2003 >Closed-Date: >Last-Modified: >Originator: Endre Nagy >Release: gcc version 3.3 20030421 (prerelease) >Organization: >Environment: Win32 -> atmel avr crosscompiler >Description: C code: for(i=25000;i;i--) {} faulty machine code (it would be OK for i-=25): ldi r18,lo8(25000) ldi r19,hi8(25000) .L10:· subi r18,lo8(-(-25)) sbci r19,hi8(-(-25)) brne .L10· C code: for(i=35000;i;i--) {} correct machine code (only initial value of i has changed): ldi r18,lo8(-30536) ldi r19,hi8(-30536) .L10: subi r18,lo8(-(-1)) sbci r19,hi8(-(-1)) brne .L10 commandline: avr-gcc -g -Wall -O2 -mmcu=at90s8515 -S -o os8515.S os8515.c >How-To-Repeat: >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2003-05-04 14:26 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-05-04 14:26 gumo [this message] 2003-05-09 8:16 Dara Hazeghi 2003-05-09 8:56 Nagy Endre
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