>Submitter-Id: net >Originator: [EMAIL PROTECTED] >Organization: The Debian project >Confidential: no >Synopsis: builtin memcmp() could be optimised >Severity: non-critical >Priority: low >Category: optimization >Class: sw-bug >Release: 3.0 (Debian GNU/Linux) and HEAD 20010701 >Environment: System: Debian GNU/Linux (testing/unstable) Architecture: i686 host: i386-linux build: i386-linux target: i386-linux configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux >Description: [ Reported to the Debian BTS as report #85535. Please CC [EMAIL PROTECTED] on replies. Log of report can be found at http://bugs.debian.org/85535 ]
int main() { return !memcmp("abcd", "efgh", 4); } produces the assembly (-S -g -O2), movl $.LC1, %edi movl $.LC0, %esi movl $4, %ecx cld repz cmpsb seta %cl setb %dl popl %esi xorl %eax, %eax popl %edi cmpb %dl, %cl sete %al which is a waste because it could've simply loaded the two objects into registers and compared them. The same is true on other architectures as well. >How-To-Repeat: >Fix: