Hi, the attached patch fixes PR65048 by checking before jump-threading that a path to be threaded is still valid: as the testcase shows, there may be paths that are not connected anymore because the cfg has changed in a previous jump-thread.
PR tree-optimization/65048 * tree-ssa-threadupdate.c (valid_jump_thread_path): New. (thread_through_all_blocks): Call valid_jump_thread_path. Remove invalid FSM jump-thread paths. * gcc.dg/tree-ssa/ssa-dom-thread-9.c: New. The patch passed bootstrap and regression tests on x86_64-linux. Ok for trunk? Thanks, Sebastian
>From 79b93a743649b898010cfea70769184bca28efb1 Mon Sep 17 00:00:00 2001 From: Sebastian Pop <seb...@gmail.com> Date: Tue, 10 Feb 2015 22:36:50 +0100 Subject: [PATCH] check that paths are still valid to be threaded PR tree-optimization/65048 * tree-ssa-threadupdate.c (valid_jump_thread_path): New. (thread_through_all_blocks): Call valid_jump_thread_path. Remove invalid FSM jump-thread paths. * gcc.dg/tree-ssa/ssa-dom-thread-9.c: New. --- gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-9.c | 49 ++++++++++++++++++++++ gcc/tree-ssa-threadupdate.c | 40 +++++++++++++++--- 2 files changed, 83 insertions(+), 6 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-9.c diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-9.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-9.c new file mode 100644 index 0000000..a843753 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-9.c @@ -0,0 +1,49 @@ +/* { dg-do compile } */ +/* { dg-options "-O3" } */ + +int a, b, c, d; +void fn (void); + +int +foo (x) +{ + switch (x) + { + case 'A': + return 'T'; + case 'U': + return 'A'; + } +} + +void +bar (int x, int y) +{ + switch (c) + { + case 'U': + switch (x) + { + default: + fn (); + case 'G': + switch (y) + { + case 'A': + d = 7; + } + } + } +} + +void +baz (void) +{ + while (1) + { + a = foo (); + b = foo (); + bar (a, b); + } +} + diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c index 3326144..7a41ab2 100644 --- a/gcc/tree-ssa-threadupdate.c +++ b/gcc/tree-ssa-threadupdate.c @@ -2473,6 +2473,21 @@ duplicate_seme_region (edge entry, edge exit, return true; } +/* Return true when PATH is a valid jump-thread path. */ + +static bool +valid_jump_thread_path (vec<jump_thread_edge *> *path) +{ + unsigned len = path->length (); + + /* Check that the path is connected. */ + for (unsigned int j = 0; j < len - 1; j++) + if ((*path)[j]->e->dest != (*path)[j+1]->e->src) + return false; + + return true; +} + /* Walk through all blocks and thread incoming edges to the appropriate outgoing edge for each edge pair recorded in THREADED_EDGES. @@ -2505,12 +2520,25 @@ thread_through_all_blocks (bool may_peel_loop_headers) vec<jump_thread_edge *> *path = paths[i]; edge entry = (*path)[0]->e; - if ((*path)[0]->type != EDGE_FSM_THREAD - /* Do not jump-thread twice from the same block. */ - || bitmap_bit_p (threaded_blocks, entry->src->index)) { - i++; - continue; - } + /* Only code-generate FSM jump-threads in this loop. */ + if ((*path)[0]->type != EDGE_FSM_THREAD) + { + i++; + continue; + } + + /* Do not jump-thread twice from the same block. */ + if (bitmap_bit_p (threaded_blocks, entry->src->index) + /* Verify that the jump thread path is still valid: a + previous jump-thread may have changed the CFG, and + invalidated the current path. */ + || !valid_jump_thread_path (path)) + { + /* Remove invalid FSM jump-thread paths. */ + delete_jump_thread_path (path); + paths.unordered_remove (i); + continue; + } unsigned len = path->length (); edge exit = (*path)[len - 1]->e; -- 1.7.2.5