https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109849
--- Comment #19 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jan Hubicka <hubi...@gcc.gnu.org>: https://gcc.gnu.org/g:9dc18fca431626404b0692c689a2e103666e7adb commit r14-2202-g9dc18fca431626404b0692c689a2e103666e7adb Author: Jan Hubicka <j...@suse.cz> Date: Thu Jun 29 22:45:37 2023 +0200 Compute ipa-predicates for conditionals involving __builtin_expect_p std::vector allocator looks as follows: __attribute__((nodiscard)) struct pair * std::__new_allocator<std::pair<unsigned int, unsigned int> >::allocate (struct __new_allocator * const this, size_type __n, const void * D.27753) { bool _1; long int _2; long int _3; long unsigned int _5; struct pair * _9; <bb 2> [local count: 1073741824]: _1 = __n_7(D) > 1152921504606846975; _2 = (long int) _1; _3 = __builtin_expect (_2, 0); if (_3 != 0) goto <bb 3>; [10.00%] else goto <bb 6>; [90.00%] <bb 3> [local count: 107374184]: if (__n_7(D) > 2305843009213693951) goto <bb 4>; [50.00%] else goto <bb 5>; [50.00%] <bb 4> [local count: 53687092]: std::__throw_bad_array_new_length (); <bb 5> [local count: 53687092]: std::__throw_bad_alloc (); <bb 6> [local count: 966367641]: _5 = __n_7(D) * 8; _9 = operator new (_5); return _9; } So there is check for allocated block size being greater than max_size which is wrapper in __builtin_expect. This makes ipa-fnsummary to give up analyzing predicates and it will miss the fact that the two different calls to __throw will be optimized out if __n is larady smaller than 1152921504606846975 which it is after _M_check_len. This patch extends ipa-fnsummary to understand functions that return their parameter. gcc/ChangeLog: PR tree-optimization/109849 * ipa-fnsummary.cc (decompose_param_expr): Skip functions returning its parameter. (set_cond_stmt_execution_predicate): Return early if predicate was constructed. gcc/testsuite/ChangeLog: PR tree-optimization/109849 * gcc.dg/ipa/pr109849.c: New test.
