Hi! The following testcase ICEs, because we have an indirect jump with a single (fake) successor edge to EXIT, one reachable from the body of the function after prologue and another one reachable from before the prologue (due to shrink-wrapping).
The patch fixes this by disallowing crossjumping of basic blocks ending in such indirect jumps with no (non-fake) successors. That condition hits on the following testcases (never during bootstrap): gcc/testsuite/gcc.c-torture/compile/20050122-2.c gcc/testsuite/gcc.c-torture/execute/920428-2.c gcc/testsuite/gcc.c-torture/execute/pr24135.c gcc/testsuite/gcc.dg/pr49994-1.c gcc/testsuite/gcc.dg/pr79494.c gcc/testsuite/gcc.dg/torture/stackalign/nested-4.c gcc/testsuite/gcc.dg/torture/stackalign/non-local-goto-3.c gcc/testsuite/gcc.dg/torture/stackalign/non-local-goto-5.c gcc/testsuite/gcc.target/i386/pr88470.c libgomp/testsuite/libgomp.c/pr81687-2.c where in most of them it is a non-local jump ending the bb; in a few of those testcases there is a crossjumping possibility, but it seems it is actually already handled during PRE (e.g. on pr24135.c). Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2018-12-13 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/88470 * cfgcleanup.c (outgoing_edges_match): If the function is shrink-wrapped and bb1 ends with a JUMP_INSN with a single fake edge to EXIT, return false. * gcc.target/i386/pr88470.c: New test. --- gcc/cfgcleanup.c.jj 2018-12-03 11:14:52.449764174 +0100 +++ gcc/cfgcleanup.c 2018-12-13 10:19:40.453539925 +0100 @@ -1592,10 +1592,13 @@ outgoing_edges_match (int mode, basic_bl if (crtl->shrink_wrapped && single_succ_p (bb1) && single_succ (bb1) == EXIT_BLOCK_PTR_FOR_FN (cfun) - && !JUMP_P (BB_END (bb1)) + && (!JUMP_P (BB_END (bb1)) + /* Punt if the only successor is a fake edge to exit, the jump + must be some weird one. */ + || (single_succ_edge (bb1)->flags & EDGE_FAKE) != 0) && !(CALL_P (BB_END (bb1)) && SIBLING_CALL_P (BB_END (bb1)))) return false; - + /* If BB1 has only one successor, we may be looking at either an unconditional jump, or a fake edge to exit. */ if (single_succ_p (bb1) --- gcc/testsuite/gcc.target/i386/pr88470.c.jj 2018-12-13 10:11:39.144381178 +0100 +++ gcc/testsuite/gcc.target/i386/pr88470.c 2018-12-13 10:10:04.610921517 +0100 @@ -0,0 +1,16 @@ +/* PR rtl-optimization/88470 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -maccumulate-outgoing-args -ftrapv -fno-ivopts -fno-reorder-blocks-and-partition" } */ + +void +foo (long x, long *y) +{ + long *a = y - 64, i; + for (i = 0; i < x; i++) + { + long v = y[i]; + *a++ = v; + } + register void **c __asm__ ("di"); + goto **c; +} Jakub