http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49018
Summary: Inline assembly block executed outside conditional check with "-O1 -ftree-vrp" Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassig...@gcc.gnu.org ReportedBy: t...@thereisnospork.com In the following test case, the int3 instruction inserted by the assertion macro is executed before any conditional check is performed when compiled with "-O1 -ftree-vrp". Without -ftree-vrp (as well as "-O2 -fno-tree-vrp"), the instructions are ordered as expected. $ cat asmvolatiletest.c #include <stdio.h> #define CUSTOM_ASSERT( X ) if( !( X ) ) { __asm__ __volatile__ ( "int3" ); } void testFunction( unsigned int a, unsigned int b ) { CUSTOM_ASSERT( a >= b ); if( a < b ) { printf( "Error: %u < %u\n", a, b ); } } $ gcc -v Using built-in specs. COLLECT_GCC=/usr/bin/gcc COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-mandriva-linux-gnu/4.6.0/lto-wrapper Target: x86_64-mandriva-linux-gnu Configured with: ./configure --build=x86_64-mandriva-linux-gnu --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/lib64 --localstatedir=/var --sharedstatedir=/usr/com --mandir=/usr/share/man --infodir=/usr/share/info --x-includes=/usr/include --x-libraries=/usr/lib64 --disable-libgcj --with-cloog --with-ppl --enable-cloog-backend=ppl --disable-libssp --disable-libunwind-exceptions --disable-werror --enable-__cxa_atexit --enable-bootstrap --enable-checking=release --enable-gnu-unique-object --enable-languages=c,ada,c++,fortran,go,lto,objc,obj-c++ --enable-linker-build-id --enable-plugin --enable-shared --enable-threads=posix --with-system-zlib --with-bugurl=https://qa.mandriva.com/ --with-tune=generic --with-arch_32=i686 --host=x86_64-mandriva-linux-gnu --target=x86_64-mandriva-linux-gnu Thread model: posix gcc version 4.6.0 20110513 (prerelease) (GCC)