http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56075
Bug #: 56075 Summary: [gcc-4.7.1] 64-bit version, -Os eliminate some line of code which working fine in gcc-4.6.2 64-bit version Classification: Unclassified Product: gcc Version: 4.7.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassig...@gcc.gnu.org ReportedBy: rajendiran.pub...@gmail.com Created attachment 29247 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29247 C source code With attached sample C codes, assembly code for C code at LINE-1 is not at all generated in gcc-4.7.1(64-bit) but gcc-4.6.2(64-bit) generate it correctly. void fun( struct semaphore *s1,struct semaphore *s2) { ... { struct semaphore __mutex = { .lock = (spinlock_t ) { { .rlock = { .raw_lock = { 0 }, .magic = 0xdead4ead, .owner_cpu = -1, .owner = ((void *)-1L), .dep_map = { .name = "(*(s1)).lock" } } } }, .count = 1, .wait_list = { &((*(s1)).wait_list), &((*(s1)).wait_list) }, }; *(s1) = __mutex; }; // LINE-1 { struct semaphore __mutex = { .lock = (spinlock_t ) { { .rlock = { .raw_lock = { 0 }, .magic = 0xdead4ead, .owner_cpu = -1, .owner = ((void *)-1L), .dep_map = { .name = "(*(s2)).lock" } } } }, .count = 1, .wait_list = { &((*(s2)).wait_list), &((*(s2)).wait_list) }, }; *(s2) = __mutex; }; //LINE-2 ... } Source Code Compiling options in GCC-4.7.1 ------------------------------------------ gcc -nostdinc -isystem /usr/lib64/gcc/x86_64-unknown-linux-gnu/4.7.1/include -I/linux-3.1.7-0/kernel/bld/include/ -I/linux-3.1.7-0/kernel/bld/arch/x86/include -Iarch/x86/include/generated -Iinclude -include /linux-3.1.7-0/kernel/bld/include/linux/kconfig.h -D__KERNEL__ -Os -m64 -fno-strict-aliasing -mno-red-zone -fno-omit-frame-pointer -fconserve-stack -S nv1.c Source Code Compiling options in GCC-4.6.2 ------------------------------------------ gcc -nostdinc -isystem /usr/lib64/gcc/x86_64-suse-linux/4.6/include -I/linux-3.1.7-0/kernel/bld/include/ -I/linux-3.1.7-0/kernel/bld/arch/x86/include -Iarch/x86/include/generated -Iinclude -include /linux-3.1.7-0/kernel/bld/include/linux/kconfig.h -D__KERNEL__ -Os -m64 -fno-strict-aliasing -mno-red-zone -fno-omit-frame-pointer -fconserve-stack -S nv1.c GCC-4.7.1 - Build Config ------------------------ Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.7.1/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../gcc-4.7.1/configure --prefix=/tmp/outdir/usr Thread model: posix gcc version 4.7.1 (GCC) GCC-4.6.2 Build Config ---------------------- Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/4.6/lto-wrapper Target: x86_64-suse-linux Configured with: ../configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64 --enable-languages=c,c++,objc,fortran,obj-c++,java,ada --enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.6 --enable-ssp --disable-libssp --disable-plugin --with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux' --disable-libgcj --disable-libmudflap --with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch --enable-version-specific-runtime-libs --program-suffix=-4.6 --enable-linux-futex --without-system-libunwind --with-arch-32=i586 --with-tune=generic --build=x86_64-suse-linux Thread model: posix gcc version 4.6.2 (SUSE Linux)