There's another latent bug in loop unrolling edge/region removal code which doesn't deal with removing edges in already removed regions.
The following fixes this. Bootstrapped on x86_64-unknown-linux-gnu, testing in progress. Richard. 2018-01-26 Richard Biener <rguent...@suse.de> PR tree-optimization/84057 * tree-ssa-loop-ivcanon.c (unloop_loops): Deal with already removed paths when removing edges. * gcc.dg/graphite/pr84057.c: New testcase. Index: gcc/tree-ssa-loop-ivcanon.c =================================================================== --- gcc/tree-ssa-loop-ivcanon.c (revision 257077) +++ gcc/tree-ssa-loop-ivcanon.c (working copy) @@ -660,14 +660,21 @@ unloop_loops (bitmap loop_closed_ssa_inv loops_to_unloop.release (); loops_to_unloop_nunroll.release (); - /* Remove edges in peeled copies. */ + /* Remove edges in peeled copies. Given remove_path removes dominated + regions we need to cope with removal of already removed paths. */ unsigned i; edge e; + auto_vec<int, 20> src_bbs; + src_bbs.reserve_exact (edges_to_remove.length ()); FOR_EACH_VEC_ELT (edges_to_remove, i, e) - { - bool ok = remove_path (e, irred_invalidated, loop_closed_ssa_invalidated); - gcc_assert (ok); - } + src_bbs.quick_push (e->src->index); + FOR_EACH_VEC_ELT (edges_to_remove, i, e) + if (BASIC_BLOCK_FOR_FN (cfun, src_bbs[i])) + { + bool ok = remove_path (e, irred_invalidated, + loop_closed_ssa_invalidated); + gcc_assert (ok); + } edges_to_remove.release (); } Index: gcc/testsuite/gcc.dg/graphite/pr84057.c =================================================================== --- gcc/testsuite/gcc.dg/graphite/pr84057.c (nonexistent) +++ gcc/testsuite/gcc.dg/graphite/pr84057.c (working copy) @@ -0,0 +1,31 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fgraphite -funroll-loops -fno-tree-ccp -fno-tree-dce" } */ + +int ue; + +void +fr (int ct) +{ + int au = 0; + int *ra = &au; + + while (au < 1) + { + au -= 0x7878788; + if (au != ct && ue != 0) + { + while (au < 1) + { + } + +fc: + while (ct != 0) + { + } + } + } + + for (au = 0; au < 2; ++au) + if (ct != 0) + goto fc; +}