Hello ! Using GCC 4.9.0 as of 20130623 : $ cat inf.c unsigned f(void) { unsigned a; int b, c, d, e; for(c = 27; c < 40; c++) b |= d |= b; if(b) a = e; return a; } $ ulimit -t 60 $ xgcc -O3 inf.c gcc: internal compiler error: CPU time limit exceeded (program cc1) Please submit a full bug report, with preprocessed source if appropriate. See <http://gcc.gnu.org/bugs.html> for instructions.
Also affects gcc-4.8-20130620, but not gcc-4.7-20130622, on x86_64-linux. A typical stack trace looks like: 0x00000000008709d5 in register_new_assert_for (expr=0x7f24dc840c60, comp_code=EQ_EXPR, val=0x7f24dc855320, bb=<optimized out>, e=0x7f24dc975310, si=..., name=<optimized out>) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:4486 4486 if (loc->comp_code == comp_code Missing separate debuginfos, use: debuginfo-install glibc-2.15-59.fc17.x86_64 (gdb) bt #0 0x00000000008709d5 in register_new_assert_for (expr=0x7f24dc840c60, comp_code=EQ_EXPR, val=0x7f24dc855320, bb=<optimized out>, e=0x7f24dc975310, si=..., name=<optimized out>) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:4486 #1 0x000000000087633b in register_edge_assert_for_1 (op=0x7f24dc840c60, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5217 #2 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #3 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #4 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #5 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #6 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #7 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #8 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #9 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #10 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #11 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #12 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #13 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #14 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #15 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #16 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #17 0x00000000008764aa in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5250 #18 0x000000000087650b in register_edge_assert_for_1 (op=<optimized out>, code=code@entry=EQ_EXPR, e=e@entry=0x7f24dc975310, bsi=...) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5252 #19 0x0000000000876886 in register_edge_assert_for (name=0x7f24dc840d38, e=e@entry=0x7f24dc975310, si=..., cond_code=<optimized out>, cond_op0=<optimized out>, cond_op1=0x7f24dc855320) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5347 #20 0x00000000008772cb in find_conditional_asserts (last=0x7f24dc960aa0, bb=0x7f24dc9551a0) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5393 #21 find_assert_locations_1 (bb=bb@entry=0x7f24dc9551a0, live=0x26d6640) at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5607 #22 0x0000000000882c19 in find_assert_locations () at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5747 #23 insert_range_assertions () at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:5935 #24 execute_vrp () at /tmp/gcc-4.8-20130620/gcc/tree-vrp.c:9287 #25 0x0000000000695785 in execute_one_pass (pass=pass@entry=0x26e2900) at /tmp/gcc-4.8-20130620/gcc/passes.c:2330 #26 0x0000000000695b45 in execute_pass_list (pass=0x26e2900) at /tmp/gcc-4.8-20130620/gcc/passes.c:2378 #27 0x0000000000695b57 in execute_pass_list (pass=0x11ca2a0) at /tmp/gcc-4.8-20130620/gcc/passes.c:2379 #28 0x00000000004f0127 in expand_function (node=0x7f24dc8486f0) at /tmp/gcc-4.8-20130620/gcc/cgraphunit.c:1640 #29 0x00000000004f1583 in expand_all_functions () at /tmp/gcc-4.8-20130620/gcc/cgraphunit.c:1744 #30 compile () at /tmp/gcc-4.8-20130620/gcc/cgraphunit.c:2042 #31 0x00000000004f1ab5 in finalize_compilation_unit () at /tmp/gcc-4.8-20130620/gcc/cgraphunit.c:2119 #32 0x00000000004275d5 in c_write_global_declarations () at /tmp/gcc-4.8-20130620/gcc/c/c-decl.c:10118 #33 0x00000000007295d5 in compile_file () at /tmp/gcc-4.8-20130620/gcc/toplev.c:557 #34 0x000000000072ac55 in do_compile () at /tmp/gcc-4.8-20130620/gcc/toplev.c:1864 #35 toplev_main (argc=19, argv=0x7fff3eee17b8) at /tmp/gcc-4.8-20130620/gcc/toplev.c:1940 #36 0x00007f24dca5e735 in __libc_start_main () from /lib64/libc.so.6 #37 0x00000000004194a1 in _start ()
Started with the PR55079 fix in r193098. The test case uses the values of uninitialized auto variables, perhaps that's confusing the compiler.
Confirmed, mine.
Hmm, it's register_edge_assert_for_1 not limiting its recursion and not avoiding duplicate visits. Which in this case leads to exponential compile-time behavior. We can mitigate the latter by only considering single-use defs.
Author: rguenth Date: Thu Aug 29 07:45:59 2013 New Revision: 202068 URL: http://gcc.gnu.org/viewcvs?rev=202068&root=gcc&view=rev Log: 2013-08-29 Richard Biener <rguenther@suse.de> PR tree-optimization/57685 * tree-vrp.c (register_edge_assert_for_1): Recurse only for single-use operands to avoid exponential complexity. * gcc.dg/torture/pr57685.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/torture/pr57685.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-vrp.c
Fixed on trunk sofar.
Author: rguenth Date: Mon Sep 9 09:48:43 2013 New Revision: 202386 URL: http://gcc.gnu.org/viewcvs?rev=202386&root=gcc&view=rev Log: 2013-09-09 Richard Biener <rguenther@suse.de> Backport from mainline 2013-08-29 Richard Biener <rguenther@suse.de> PR tree-optimization/57685 * tree-vrp.c (register_edge_assert_for_1): Recurse only for single-use operands to avoid exponential complexity. * gcc.dg/torture/pr57685.c: New testcase. Added: branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr57685.c Modified: branches/gcc-4_8-branch/gcc/ChangeLog branches/gcc-4_8-branch/gcc/testsuite/ChangeLog branches/gcc-4_8-branch/gcc/tree-vrp.c
Fixed.