https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78819
Bug ID: 78819 Summary: [7 Regression] Wrong code with VRP caused by register assertions along default switch labels Product: gcc Version: unknown Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: marxin at gcc dot gnu.org CC: ppalka at gcc dot gnu.org Target Milestone: --- Started with r238761, following test-case behaves wrongly: $ cat /tmp/testcase.c #include <stdio.h> #include <stdlib.h> int main(unsigned argc, char **argv) { if (argc <= 0) return 0; if (argc > 3) return 0; switch (argc) { case 1: case 3: fprintf (stderr, "value: %d\n", argc); break; case 2: fprintf (stderr, "value: %d\n", argc); break; default: abort(); } return 1; } $ ./xgcc -B. /tmp/testcase.c -O0 -fdump-tree-optimized && ./a.out 1 1 value: 3 $ ./xgcc -B. /tmp/testcase.c -O2 -fdump-tree-optimized && ./a.out 1 1 value: 1 This miscompilation is detected by Python-2.7.12 package, that fails in test_epoll test-case. Thanks, Martin