https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67470
Bug ID: 67470 Summary: ICE at -O3 on x86_64-linux-gnu in compute_live_loop_exits, at tree-ssa-loop-manip.c:235 Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: su at cs dot ucdavis.edu Target Milestone: --- The following code causes an ICE when compiled with the current gcc trunk (as well as 5.1.x and 5.2.x) at -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes. It is a regression from 4.9.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 20150906 (experimental) [trunk revision 227511] (GCC) $ $ gcc-trunk -O2 small.c; ./a.out $ gcc-4.9 -O3 small.c; ./a.out $ $ gcc-trunk -O3 small.c small.c: In function ‘main’: small.c:6:1: internal compiler error: in compute_live_loop_exits, at tree-ssa-loop-manip.c:235 main () ^ 0xc070b7 compute_live_loop_exits ../../gcc-trunk/gcc/tree-ssa-loop-manip.c:235 0xc070b7 add_exit_phis_var ../../gcc-trunk/gcc/tree-ssa-loop-manip.c:322 0xc070b7 add_exit_phis ../../gcc-trunk/gcc/tree-ssa-loop-manip.c:344 0xc070b7 rewrite_into_loop_closed_ssa_1(bitmap_head*, unsigned int, int, loop*) ../../gcc-trunk/gcc/tree-ssa-loop-manip.c:664 0xbeabb4 move_computations ../../gcc-trunk/gcc/tree-ssa-loop-im.c:1326 0xbeabb4 tree_ssa_lim() ../../gcc-trunk/gcc/tree-ssa-loop-im.c:2551 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <http://gcc.gnu.org/bugs.html> for instructions. $ ----------------------------------- int a, b, *c, d, e; void __assert_fail (); int main () { int f, *g, **h = &g; for (; b;) { c = &a; for (e = 0; e < 1; e++) *h = 0; for (; d; d++) if (f) *c = 0; else { *c = e = 0; *h = &a; } if (a && !g) __assert_fail (); } return 0; }