https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68250
Bug ID: 68250 Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu (in 64-bit mode) Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: su at cs dot ucdavis.edu Target Milestone: --- The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O2 and -O3 in the 64-bit mode (but not in the 32-bit mode). This is a regression from 5.2.x. $ gcc-trunk -v Using built-in specs. COLLECT_GCC=gcc-trunk COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk --enable-languages=c,c++ --disable-werror --enable-multilib Thread model: posix gcc version 6.0.0 20151107 (experimental) [trunk revision 229937] (GCC) $ $ gcc-trunk -m64 -Os small.c; ./a.out 1 $ gcc-trunk -m32 -O2 small.c; ./a.out 1 $ gcc-5.2 -m64 -O2 small.c; ./a.out 1 $ $ gcc-trunk -m64 -O2 small.c $ ./a.out 0 $ ---------------------------------------- int printf (const char *, ...); char a, b, h, k, l, m, o; short c, d, n; int e, f, g, j, q; void fn1 () { int p = b || a; n = o > 0 || d > 1 >> o ? d : d << o; for (; j; j++) m = c < 0 || m || c << p; l = f + 1; for (; f < 1; f = 1) k = h + 1; } int main () { char i; for (; e < 1; e++) { fn1 (); if (k) i = k; if (i > q) g = 0; } printf ("%d\n", k); return 0; }