https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63947
Bug ID: 63947 Summary: Wrong assembly code generation Product: gcc Version: 4.9.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: ishiura-compiler at ml dot kwansei.ac.jp GCC 4.9.2 for x86_64 miscompiles the following code with optimize option -Os. $ cat error.c unsigned int a = 0U; int t = 0; int main (void) { int b = 0; volatile int c = 0; long double d = 1.0L; int e = 0; t = (((b+e)/d)-(a>(c+a))); return 0; } $ x86_64-unknown-linux-gnu-gcc-4.9.2 error.c -Os /tmp/ccjhNwLd.s: Assembler messages: /tmp/ccjhNwLd.s:18: Error: no such instruction: `fcmovnc %st(1),%st' $ x86_64-unknown-linux-gnu-gcc-4.9.2 -v Using built-in specs. COLLECT_GCC=x86_64-unknown-linux-gnu-gcc-4.9.2 COLLECT_LTO_WRAPPER=/usr/local/x86_64-tools/gcc-4.9.2/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../configure --prefix=/usr/local/x86_64-tools/gcc-4.9.2/ --with-gmp=/usr/local/gmp-5.0.5/ --with-mpfr=/usr/local/mpfr-3.1.0/ --with-mpc=/usr/local/mpc-0.9/ --disable-multilib --disable-nls --enable-languages=c Thread model: posix gcc version 4.9.2 (GCC)