> On Jul 31, 2017, at 8:19 AM, Bill Schmidt <wschm...@linux.vnet.ibm.com> wrote:
>
> That would certainly be much simpler! I'll regstrap it and test it on the
> other
> occurrence I've found to be certain.
Unfortunately, this fails bootstrap:
/home/wschmidt/gcc/gcc-mainline-test/gcc/calls.c: In function 'rtx_def*
emit_library_call_value_1(int, rtx, rtx, libcall_type, machine_mode, int,
va_list)':
/home/wschmidt/gcc/gcc-mainline-test/gcc/calls.c:4362:1: error: definition in
block 214 does not dominate use in block 14
emit_library_call_value_1 (int retval, rtx orgfun, rtx value,
^~~~~~~~~~~~~~~~~~~~~~~~~
for SSA_NAME: slsr_772 in statement:
slsr_749 = PHI <_17(26), slsr_772(14), slsr_334(214)>
PHI argument
slsr_772
for PHI node
slsr_749 = PHI <_17(26), slsr_772(14), slsr_334(214)>
during GIMPLE pass: slsr
/home/wschmidt/gcc/gcc-mainline-test/gcc/calls.c:4362:1: internal compiler
error: verify_ssa failed
0x11567cf3 verify_ssa(bool, bool)
/home/wschmidt/gcc/gcc-mainline-test/gcc/tree-ssa.c:1186
0x10fc3fff execute_function_todo
/home/wschmidt/gcc/gcc-mainline-test/gcc/passes.c:1997
0x10fc277f do_per_function
/home/wschmidt/gcc/gcc-mainline-test/gcc/passes.c:1655
0x10fc42a3 execute_todo
/home/wschmidt/gcc/gcc-mainline-test/gcc/passes.c:2044
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Not terribly surprising given how sensitive this stuff is. I can look into why
this fails, but looks like it can't be quite this simple, sadly.
Bill
>
> -- Bill
>
>> On Jul 31, 2017, at 4:15 AM, Richard Biener <richard.guent...@gmail.com>
>> wrote:
>>
>> On Sun, Jul 30, 2017 at 8:04 PM, Bill Schmidt
>> <wschm...@linux.vnet.ibm.com> wrote:
>>> Hi,
>>>
>>> PR81354 identifies a latent bug that can happen in SLSR since the
>>> conditional candidate support was first added. SLSR relies on the
>>> address of a GIMPLE PHI remaining constant during the course of the
>>> optimization pass, but it needs to split edges. The use of
>>> make_single_succ_edge and reinstall_phi_args in gimple_split_edge
>>> causes GIMPLE PHI statements to be temporarily expanded to add a
>>> predecessor, and then rebuilt to have the original number of
>>> predecessors. The expansion usually, if not always, causes the PHI
>>> statement to change address. Thus gimple_split_edge needs to be
>>> rewritten to perform in-situ replacement of PHI arguments.
>>>
>>> The required pieces of make_single_succ_edge have been extracted into
>>> two places: make_replacement_pred_edge, and some fixup code at the
>>> end of gimple_split_edge. The division is necessary because the
>>> destination of the original edge must remember its original
>>> predecessors for the switch processing in
>>> gimple_redirect_edge_and_branch_1 to work properly.
>>>
>>> The function gimple_redirect_edge_and_branch was factored into two
>>> pieces so that most of it can be used by gimple_split_edge without
>>> calling ssa_redirect_edge, which also interferes with PHIs. The
>>> useful bits of ssa_redirect_edge are factored out into the next three
>>> lines of gimple_split_edge.
>>>
>>> Similarly, redirect_eh_edge had already been similarly factored into
>>> redirect_eh_edge_1 and ssa_redirect_edge. I took advantage of that
>>> and exposed redirect_eh_edge_1 for use in gimple_redirect_edge_and_branch_1.
>>>
>>> I've added the test from PR81354 as a torture test, but as we've seen,
>>> small changes elsewhere in the optimizer can easily hide the problem.
>>>
>>> Bootstrapped and tested on powerpc64le-linux-gnu with no regressions.
>>> Is this ok for trunk? Eventually this needs to be backported to GCC 5,
>>> 6, and 7 if that's acceptable, since PR81354 was observed on
>>> gcc-5-branch. I haven't yet prepared the backports.
>>
>> I don't like make_replacement_pred_edge too much. Wouldn't it work
>> to make sure we first shrink and then re-grow like if we simply do the
>> redirect_edge_and_branch before the make_single_succ_edge call?
>> At least quick testing shows it fixes the testcase on the GCC 6 branch for
>> me.
>>
>> Index: gcc/tree-cfg.c
>> ===================================================================
>> --- gcc/tree-cfg.c (revision 250732)
>> +++ gcc/tree-cfg.c (working copy)
>> @@ -2753,12 +2753,16 @@ gimple_split_edge (edge edge_in)
>> new_bb = create_empty_bb (after_bb);
>> new_bb->frequency = EDGE_FREQUENCY (edge_in);
>> new_bb->count = edge_in->count;
>> +
>> + /* First redirect the existing edge to avoid reallocating
>> + PHI nodes in dest. */
>> + e = redirect_edge_and_branch (edge_in, new_bb);
>> + gcc_assert (e == edge_in);
>> +
>> new_edge = make_edge (new_bb, dest, EDGE_FALLTHRU);
>> new_edge->probability = REG_BR_PROB_BASE;
>> new_edge->count = edge_in->count;
>>
>> - e = redirect_edge_and_branch (edge_in, new_bb);
>> - gcc_assert (e == edge_in);
>> reinstall_phi_args (new_edge, e);
>>
>> return new_bb;
>>
>> Sorry for misleading you to a complex solution.
>>
>> Thanks,
>> Richard.
>>
>>> Thanks,
>>> Bill
>>>
>>>
>>> [gcc]
>>>
>>> 2017-07-30 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>>>
>>> PR tree-optimization/81354
>>> * tree-cfg.c (gimple_redirect_edge_and_branch_1): New decl.
>>> (reinstall_phi_args): Delete function.
>>> (make_replacement_pred_edge): New function.
>>> (gimple_split_edge): Rewrite.
>>> (gimple_redirect_edge_and_branch_1): New function, factored
>>> from...
>>> (gimple_redirect_edge_and_branch): ...here.
>>> (split_critical_edges): Don't re-split already split edges.
>>> * tree-eh.c (redirect_eh_edge_1): Make visible.
>>> * tree-eh.h (redirect_eh_edge_1): Likewise.
>>>
>>> [gcc/testsuite]
>>>
>>> 2017-07-30 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>>>
>>> PR tree-optimization/81354
>>> * g++.dg/torture/pr81354.C: New file.
>>>
>>>
>>> Index: gcc/testsuite/g++.dg/torture/pr81354.C
>>> ===================================================================
>>> --- gcc/testsuite/g++.dg/torture/pr81354.C (nonexistent)
>>> +++ gcc/testsuite/g++.dg/torture/pr81354.C (working copy)
>>> @@ -0,0 +1,24 @@
>>> +// PR81354 reported this test as crashing in a limited range of revisions.
>>> +// { dg-do compile }
>>> +
>>> +struct T { double a; double b; };
>>> +
>>> +void foo(T Ad[], int As[2])
>>> +{
>>> + int j;
>>> + int i;
>>> + int Bs[2] = {0,0};
>>> + T Bd[16];
>>> +
>>> + for (j = 0; j < 4; j++) {
>>> + for (i = 0; i + 1 <= j + 1; i++) {
>>> + Ad[i + As[0] * j] = Bd[i + Bs[0] * j];
>>> + }
>>> +
>>> + i = j + 1; // <- comment out this line and it does not crash
>>> + for (; i + 1 < 5; i++) {
>>> + Ad[i + As[0] * j].a = 0.0;
>>> + Ad[i + As[0] * j].b = 0.0;
>>> + }
>>> + }
>>> +}
>>> Index: gcc/tree-cfg.c
>>> ===================================================================
>>> --- gcc/tree-cfg.c (revision 250721)
>>> +++ gcc/tree-cfg.c (working copy)
>>> @@ -154,6 +154,7 @@ static void make_gimple_switch_edges (gswitch *, b
>>> static bool make_goto_expr_edges (basic_block);
>>> static void make_gimple_asm_edges (basic_block);
>>> static edge gimple_redirect_edge_and_branch (edge, basic_block);
>>> +static edge gimple_redirect_edge_and_branch_1 (edge, basic_block);
>>> static edge gimple_try_redirect_by_replacing_jump (edge, basic_block);
>>>
>>> /* Various helpers. */
>>> @@ -2776,35 +2777,6 @@ last_and_only_stmt (basic_block bb)
>>> return NULL;
>>> }
>>>
>>> -/* Reinstall those PHI arguments queued in OLD_EDGE to NEW_EDGE. */
>>> -
>>> -static void
>>> -reinstall_phi_args (edge new_edge, edge old_edge)
>>> -{
>>> - edge_var_map *vm;
>>> - int i;
>>> - gphi_iterator phis;
>>> -
>>> - vec<edge_var_map> *v = redirect_edge_var_map_vector (old_edge);
>>> - if (!v)
>>> - return;
>>> -
>>> - for (i = 0, phis = gsi_start_phis (new_edge->dest);
>>> - v->iterate (i, &vm) && !gsi_end_p (phis);
>>> - i++, gsi_next (&phis))
>>> - {
>>> - gphi *phi = phis.phi ();
>>> - tree result = redirect_edge_var_map_result (vm);
>>> - tree arg = redirect_edge_var_map_def (vm);
>>> -
>>> - gcc_assert (result == gimple_phi_result (phi));
>>> -
>>> - add_phi_arg (phi, arg, new_edge, redirect_edge_var_map_location
>>> (vm));
>>> - }
>>> -
>>> - redirect_edge_var_map_clear (old_edge);
>>> -}
>>> -
>>> /* Returns the basic block after which the new basic block created
>>> by splitting edge EDGE_IN should be placed. Tries to keep the new block
>>> near its "logical" location. This is of most help to humans looking
>>> @@ -2825,6 +2797,24 @@ split_edge_bb_loc (edge edge_in)
>>> return dest_prev;
>>> }
>>>
>>> +/* Create a single-predecessor edge from SRC to DST, replacing the
>>> + predecessor edge E_IN of DST, with flags FLAGS. This is done in
>>> + situ so that phis in DST will not get re-allocated. */
>>> +
>>> +static edge
>>> +make_replacement_pred_edge (basic_block src, basic_block dest,
>>> + edge e_in, int flags)
>>> +{
>>> + edge e = ggc_cleared_alloc<edge_def> ();
>>> + n_edges_for_fn (cfun)++;
>>> + e->src = src;
>>> + e->dest = dest;
>>> + e->flags = flags;
>>> + vec_safe_push (src->succs, e);
>>> + e->dest_idx = e_in->dest_idx;
>>> + return e;
>>> +}
>>> +
>>> /* Split a (typically critical) edge EDGE_IN. Return the new block.
>>> Abort on abnormal edges. */
>>>
>>> @@ -2832,7 +2822,7 @@ static basic_block
>>> gimple_split_edge (edge edge_in)
>>> {
>>> basic_block new_bb, after_bb, dest;
>>> - edge new_edge, e;
>>> + edge e, f;
>>>
>>> /* Abnormal edges cannot be split. */
>>> gcc_assert (!(edge_in->flags & EDGE_ABNORMAL));
>>> @@ -2841,15 +2831,33 @@ gimple_split_edge (edge edge_in)
>>>
>>> after_bb = split_edge_bb_loc (edge_in);
>>>
>>> + /* Create a new block, and an edge F from that block to the original
>>> + destination. */
>>> new_bb = create_empty_bb (after_bb);
>>> new_bb->frequency = EDGE_FREQUENCY (edge_in);
>>> new_bb->count = edge_in->count;
>>> - new_edge = make_single_succ_edge (new_bb, dest, EDGE_FALLTHRU);
>>> + f = make_replacement_pred_edge (new_bb, dest, edge_in, EDGE_FALLTHRU);
>>>
>>> - e = redirect_edge_and_branch (edge_in, new_bb);
>>> + /* Redirect the original edge to its new successor. */
>>> + e = gimple_redirect_edge_and_branch_1 (edge_in, new_bb);
>>> gcc_assert (e == edge_in);
>>> - reinstall_phi_args (new_edge, e);
>>> + e->dest = new_bb;
>>> + vec_safe_push (new_bb->preds, e);
>>> + e->dest_idx = 0;
>>>
>>> + /* Fix up the predecessor edge for DEST to now be F. We can't do
>>> + this prior to gimple_redirect_edge_and_branch_1 without raising
>>> + havoc in the switch code. */
>>> + int idx = -1;
>>> + for (unsigned int i = 0; i < EDGE_COUNT (dest->preds); i++)
>>> + if (EDGE_PRED (dest, i) == edge_in)
>>> + {
>>> + idx = i;
>>> + break;
>>> + }
>>> + gcc_assert (idx != -1);
>>> + EDGE_PRED (dest, idx) = f;
>>> +
>>> return new_bb;
>>> }
>>>
>>> @@ -5740,12 +5748,10 @@ gimple_try_redirect_by_replacing_jump (edge e, bas
>>> return NULL;
>>> }
>>>
>>> +/* Primary worker for gimple_redirect_edge_and_branch. */
>>>
>>> -/* Redirect E to DEST. Return NULL on failure. Otherwise, return the
>>> - edge representing the redirected branch. */
>>> -
>>> static edge
>>> -gimple_redirect_edge_and_branch (edge e, basic_block dest)
>>> +gimple_redirect_edge_and_branch_1 (edge e, basic_block dest)
>>> {
>>> basic_block bb = e->src;
>>> gimple_stmt_iterator gsi;
>>> @@ -5759,7 +5765,10 @@ static edge
>>> return NULL;
>>>
>>> if (e->flags & EDGE_EH)
>>> - return redirect_eh_edge (e, dest);
>>> + {
>>> + redirect_eh_edge_1 (e, dest, false);
>>> + return e;
>>> + }
>>>
>>> if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
>>> {
>>> @@ -5887,9 +5896,19 @@ static edge
>>> gcc_assert (e->flags & EDGE_FALLTHRU);
>>> break;
>>> }
>>> + return e;
>>> +}
>>>
>>> - /* Update/insert PHI nodes as necessary. */
>>> +/* Redirect E to DEST. Return NULL on failure. Otherwise, return the
>>> + edge representing the redirected branch. */
>>>
>>> +static edge
>>> +gimple_redirect_edge_and_branch (edge e, basic_block dest)
>>> +{
>>> + edge f = gimple_redirect_edge_and_branch_1 (e, dest);
>>> + if (f != e)
>>> + return f;
>>> +
>>> /* Now update the edges in the CFG. */
>>> e = ssa_redirect_edge (e, dest);
>>>
>>> @@ -8636,13 +8655,18 @@ split_critical_edges (void)
>>> basic_block bb;
>>> edge e;
>>> edge_iterator ei;
>>> + int first_free_block;
>>>
>>> /* split_edge can redirect edges out of SWITCH_EXPRs, which can get
>>> expensive. So we want to enable recording of edge to CASE_LABEL_EXPR
>>> mappings around the calls to split_edge. */
>>> start_recording_case_labels ();
>>> + first_free_block = last_basic_block_for_fn (cfun);
>>> FOR_ALL_BB_FN (bb, cfun)
>>> {
>>> + /* Don't re-split edges we've already split. */
>>> + if (bb->index >= first_free_block)
>>> + continue;
>>> FOR_EACH_EDGE (e, ei, bb->succs)
>>> {
>>> if (EDGE_CRITICAL_P (e) && !(e->flags & EDGE_ABNORMAL))
>>> Index: gcc/tree-eh.c
>>> ===================================================================
>>> --- gcc/tree-eh.c (revision 250721)
>>> +++ gcc/tree-eh.c (working copy)
>>> @@ -2279,7 +2279,7 @@ make_eh_edges (gimple *stmt)
>>> If false, we're being called from generic cfg manipulation code and we
>>> should preserve our place within the region tree. */
>>>
>>> -static void
>>> +void
>>> redirect_eh_edge_1 (edge edge_in, basic_block new_bb, bool change_region)
>>> {
>>> eh_landing_pad old_lp, new_lp;
>>> Index: gcc/tree-eh.h
>>> ===================================================================
>>> --- gcc/tree-eh.h (revision 250721)
>>> +++ gcc/tree-eh.h (working copy)
>>> @@ -32,6 +32,7 @@ extern int lookup_stmt_eh_lp (gimple *);
>>> extern bool make_eh_dispatch_edges (geh_dispatch *);
>>> extern void make_eh_edges (gimple *);
>>> extern edge redirect_eh_edge (edge, basic_block);
>>> +extern void redirect_eh_edge_1 (edge, basic_block, bool);
>>> extern void redirect_eh_dispatch_edge (geh_dispatch *, edge, basic_block);
>>> extern bool operation_could_trap_helper_p (enum tree_code, bool, bool, bool,
>>> bool, tree, bool *);
>
