https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70771
Bug ID: 70771 Summary: ICE on valid code at -O3 on x86_64-linux-gnu in operator[], at vec.h:714 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 at -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes. It is a regression from 5.3.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/7.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto --prefix=/usr/local/gcc-trunk --disable-bootstrap Thread model: posix gcc version 7.0.0 20160423 (experimental) [trunk revision 235384] (GCC) $ $ gcc-trunk -O2 small.c; ./a.out $ gcc-5.3 -O3 small.c; ./a.out $ $ gcc-trunk -O3 small.c small.c: In function ‘main’: small.c:18:1: internal compiler error: in operator[], at vec.h:714 main () ^~~~ 0xba5e89 vec<edge_def*, va_gc, vl_embed>::operator[](unsigned int) ../../gcc-source-trunk/gcc/vec.h:714 0xba5e89 gimple_phi_arg_edge ../../gcc-source-trunk/gcc/gimple.h:4339 0xba5e89 replace_uses_by(tree_node*, tree_node*) ../../gcc-source-trunk/gcc/tree-cfg.c:1818 0xba60b1 gimple_merge_blocks ../../gcc-source-trunk/gcc/tree-cfg.c:1938 0x74cf75 merge_blocks(basic_block_def*, basic_block_def*) ../../gcc-source-trunk/gcc/cfghooks.c:787 0xbaecc4 cleanup_tree_cfg_bb ../../gcc-source-trunk/gcc/tree-cfgcleanup.c:660 0xbaf598 cleanup_tree_cfg_1 ../../gcc-source-trunk/gcc/tree-cfgcleanup.c:710 0xbaf598 cleanup_tree_cfg_noloop ../../gcc-source-trunk/gcc/tree-cfgcleanup.c:761 0xbaf598 cleanup_tree_cfg() ../../gcc-source-trunk/gcc/tree-cfgcleanup.c:812 0xa9ad74 execute_function_todo ../../gcc-source-trunk/gcc/passes.c:1921 0xa9b7cb execute_todo ../../gcc-source-trunk/gcc/passes.c:2020 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; static void fn1 () { for (b = 0; b < 1; b++) for (c = 0; c < 1; c++) { if (a) break; b = 1; } for (;;) ; } int main () { if (d) fn1 (); return 0; }