On Mon, Jul 31, 2017 at 4:03 PM, Bill Schmidt
<wschm...@linux.vnet.ibm.com> wrote:
>
>> 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.
Intersting ... a dg-torture.exp run was clean for me (all I
tested...). So yes, can you
check what fails? Maybe run the testsuite with the stage1 compiler.
Richard.
> 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 *);
>>
>
