On Mon, May 10, 2021 at 8:52 PM Martin Jambor <mjam...@suse.cz> wrote:
>
> Hi,
>
> On Mon, May 10 2021, Richard Biener wrote:
> > I've tried to have a look at this patch but it does a lot of IPA specific
> > refactoring(?), so the actual DCE bits are hard to find. Is it possible
> > to split the patch up or is it too entangled?
> >
>
> Yes:
>
> I was asked by Richi to split my fix for PR 93385 for easier review
> into IPA-SRA materialization refactoring and the actual DCE addition.
> This is the second part that actually contains the DCE of statements
> that IPA-SRA should not leave behind because they can have problematic
> side effects, even if they are useless, so that we do not depend on
> tree-dce to remove them for correctness.
>
> The patch fixes the problem by doing a def-use walk when materializing
> clones, marking which statements should not be copied and which
> SSA_NAMEs do not need to be computed because eventually they would be
> DCEd. We do this on the original function body and tree-inline simply
> does not copy statements which are "dead."
>
> The only complication is removing dead argument calls because that
> needs to be communicated to callee redirection code using the
> infrastructure introduced by the previous patch.
>
> I added all testcases of the original patch to this one, although some
> probably test behavior introduced in the previous patch.
>
> The patch is so far only lightly tested but I have verified that
> together with the second one they make up pretty much exactly the
> original one (modulo m_new_call_arg_modification_info) which I did
> bootstrap this morning. I will of course bootstrap it independently
> too.
>
> What do you think?
>
> Martin
>
>
> gcc/ChangeLog:
>
> 2021-05-10 Martin Jambor <mjam...@suse.cz>
>
> PR ipa/93385
> * ipa-param-manipulation.h (class ipa_param_body_adjustments): New
> members m_dead_stmts and m_dead_ssas.
> * ipa-param-manipulation.c (phi_arg_will_live_p): New function.
> (ipa_param_body_adjustments::mark_dead_statements): Likwise.
> (ipa_param_body_adjustments::common_initialization): Call it on
> all removed but not split parameters.
> (ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
> new mwmbers.
> (ipa_param_body_adjustments::modify_call_stmt): Remove arguments that
> are dead.
> * tree-inline.c (remap_gimple_stmt): Do not copy dead statements,
> reset
> dead debug statements.
> (copy_phis_for_bb): Do not copy dead PHI nodes.
>
> gcc/testsuite/ChangeLog:
>
> 2021-03-22 Martin Jambor <mjam...@suse.cz>
>
> PR ipa/93385
> * gcc.dg/ipa/pr93385.c: New test.
> * gcc.dg/ipa/ipa-sra-23.c: Likewise.
> * gcc.dg/ipa/ipa-sra-24.c: Likewise.
> * g++.dg/ipa/ipa-sra-4.C: Likewise.
> ---
> gcc/ipa-param-manipulation.c | 142 +++++++++++++++++++++++---
> gcc/ipa-param-manipulation.h | 6 ++
> gcc/testsuite/g++.dg/ipa/ipa-sra-4.C | 37 +++++++
> gcc/testsuite/gcc.dg/ipa/ipa-sra-23.c | 24 +++++
> gcc/testsuite/gcc.dg/ipa/ipa-sra-24.c | 20 ++++
> gcc/testsuite/gcc.dg/ipa/pr93385.c | 27 +++++
> gcc/tree-inline.c | 18 +++-
> 7 files changed, 256 insertions(+), 18 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/ipa/ipa-sra-4.C
> create mode 100644 gcc/testsuite/gcc.dg/ipa/ipa-sra-23.c
> create mode 100644 gcc/testsuite/gcc.dg/ipa/ipa-sra-24.c
> create mode 100644 gcc/testsuite/gcc.dg/ipa/pr93385.c
>
> diff --git a/gcc/ipa-param-manipulation.c b/gcc/ipa-param-manipulation.c
> index 424b8e5343f..d7d73542856 100644
> --- a/gcc/ipa-param-manipulation.c
> +++ b/gcc/ipa-param-manipulation.c
> @@ -969,6 +969,97 @@ ipa_param_body_adjustments::carry_over_param (tree t)
> return new_parm;
> }
>
> +/* Return true if BLOCKS_TO_COPY is NULL or if PHI has an argument ARG in
> + position that corresponds to an edge that is coming from a block that has
> + the corresponding bit set in BLOCKS_TO_COPY. */
> +
> +static bool
> +phi_arg_will_live_p (gphi *phi, bitmap blocks_to_copy, tree arg)
> +{
> + bool arg_will_survive = false;
> + if (!blocks_to_copy)
> + arg_will_survive = true;
> + else
> + for (unsigned i = 0; i < gimple_phi_num_args (phi); i++)
> + if (gimple_phi_arg_def (phi, i) == arg
I think this is prone to quadratic, it would be nice to use the
faster FOR_EACH_IMM_USE_FAST () below and then
phi_arg_index_from_use () to get to the corresponding edge
directly - this would remove the loop over PHI args here and
you can then inline the function below.
> + && bitmap_bit_p (blocks_to_copy,
> + gimple_phi_arg_edge (phi, i)->src->index))
> + {
> + arg_will_survive = true;
> + break;
> + }
> + return arg_will_survive;
> +}
> +
> +/* Populate m_dead_stmts given that DEAD_PARAM is going to be removed without
> + any replacement or splitting. REPL is the replacement VAR_SECL to base
> any
> + remaining uses of a removed parameter on. */
> +
> +void
> +ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> +{
> + /* Current IPA analyses which remove unused parameters never remove a
> + non-gimple register ones which have any use except as parameters in
> other
> + calls, so we can safely leve them as they are. */
> + if (!is_gimple_reg (dead_param))
> + return;
> + tree parm_ddef = ssa_default_def (m_id->src_cfun, dead_param);
> + if (!parm_ddef || has_zero_uses (parm_ddef))
> + return;
> +
> + auto_vec<tree, 4> stack;
> + m_dead_ssas.add (parm_ddef);
> + stack.safe_push (parm_ddef);
> + while (!stack.is_empty ())
> + {
> + tree t = stack.pop ();
> +
> + imm_use_iterator imm_iter;
> + gimple *stmt;
> +
> + insert_decl_map (m_id, t, error_mark_node);
> + FOR_EACH_IMM_USE_STMT (stmt, imm_iter, t)
> + {
> + if (is_gimple_call (stmt)
(*) so we just ignore dead calls? That is, there might be
a const call like
_1 = foo (removed_param_2);
and followup important to be removed uses of _1? Above
you say that eventual IPA SRA argument removal is dealt
with but this still leaves the const/pure call case. Unless
IPA SRA bails on them, of course.
Can you add a comment like
/* IPA SRA only handles dead arguments in calls when it
removes those arguments from the called function. The
IPA machinery arranges for fixup here. */
> + || (m_id->blocks_to_copy
> + && !bitmap_bit_p (m_id->blocks_to_copy,
> + gimple_bb (stmt)->index)))
> + continue;
> +
> + if (is_gimple_debug (stmt))
> + {
> + m_dead_stmts.add (stmt);
> + gcc_assert (gimple_debug_bind_p (stmt));
> + }
> + else if (gimple_code (stmt) == GIMPLE_PHI)
> + {
> + gphi *phi = as_a <gphi *> (stmt);
> + if (phi_arg_will_live_p (phi, m_id->blocks_to_copy, t))
> + {
> + m_dead_stmts.add (phi);
> + tree res = gimple_phi_result (phi);
> + if (!m_dead_ssas.add (res))
> + stack.safe_push (res);
> + }
> + }
> + else if (is_gimple_assign (stmt))
> + {
> + m_dead_stmts.add (stmt);
> + if (!gimple_clobber_p (stmt))
> + {
> + tree lhs = gimple_assign_lhs (stmt);
> + gcc_assert (TREE_CODE (lhs) == SSA_NAME);
I don't think you can assert this? Well, maybe you can because
IPA prop would have refused to mark the param dead? I'm
thinking about stores here. I'd have leaned towards instead
guarding the m_dead_ssas.add with TREE_CODE (lhs) == SSA_NAME
but this then leaves possibly "dead" code around when it is not
an SSA name.
> + if (!m_dead_ssas.add (lhs))
> + stack.safe_push (lhs);
> + }
> + }
> + else
> + /* IPA-SRA does not analyze other types of statements. */
> + gcc_unreachable ();
So I guess fine in this light. But (*) above.
Otherwise looks OK to me.
Richard.
> + }
> + }
> +}
> +
> /* Common initialization performed by all ipa_param_body_adjustments
> constructors. OLD_FNDECL is the declaration we take original arguments
> from, (it may be the same as M_FNDECL). VARS, if non-NULL, is a pointer
> to
> @@ -1002,6 +1093,9 @@ ipa_param_body_adjustments::common_initialization (tree
> old_fndecl,
> auto_vec<bool, 16> kept;
> kept.reserve_exact (m_oparms.length ());
> kept.quick_grow_cleared (m_oparms.length ());
> + auto_vec<bool, 16> split;
> + split.reserve_exact (m_oparms.length ());
> + split.quick_grow_cleared (m_oparms.length ());
>
> unsigned adj_len = vec_safe_length (m_adj_params);
> m_method2func = ((TREE_CODE (TREE_TYPE (m_fndecl)) == METHOD_TYPE)
> @@ -1047,6 +1141,7 @@ ipa_param_body_adjustments::common_initialization (tree
> old_fndecl,
> if (apm->op == IPA_PARAM_OP_SPLIT)
> {
> m_split_modifications_p = true;
> + split[prev_index] = true;
> register_replacement (apm, new_parm);
> }
> }
> @@ -1079,6 +1174,11 @@ ipa_param_body_adjustments::common_initialization
> (tree old_fndecl,
> /* Declare this new variable. */
> DECL_CHAIN (var) = *vars;
> *vars = var;
> +
> + /* If this is not a split but a real removal, init hash sets
> + that will guide what not to copy to the new body. */
> + if (!split[i])
> + mark_dead_statements (m_oparms[i]);
> }
> }
> else
> @@ -1135,9 +1235,10 @@ ipa_param_body_adjustments
> ::ipa_param_body_adjustments (vec<ipa_adjusted_param, va_gc> *adj_params,
> tree fndecl)
> : m_adj_params (adj_params), m_adjustments (NULL), m_reset_debug_decls (),
> - m_split_modifications_p (false), m_fndecl (fndecl), m_id (NULL),
> - m_oparms (), m_new_decls (), m_new_types (), m_replacements (),
> - m_removed_decls (), m_removed_map (), m_method2func (false)
> + m_split_modifications_p (false), m_dead_stmts (), m_dead_ssas (),
> + m_fndecl (fndecl), m_id (NULL), m_oparms (), m_new_decls (),
> + m_new_types (), m_replacements (), m_removed_decls (), m_removed_map (),
> + m_method2func (false)
> {
> common_initialization (fndecl, NULL, NULL);
> }
> @@ -1151,9 +1252,9 @@ ipa_param_body_adjustments
> ::ipa_param_body_adjustments (ipa_param_adjustments *adjustments,
> tree fndecl)
> : m_adj_params (adjustments->m_adj_params), m_adjustments (adjustments),
> - m_reset_debug_decls (), m_split_modifications_p (false), m_fndecl
> (fndecl),
> - m_id (NULL), m_oparms (), m_new_decls (), m_new_types (),
> - m_replacements (), m_removed_decls (), m_removed_map (),
> + m_reset_debug_decls (), m_split_modifications_p (false), m_dead_stmts (),
> + m_dead_ssas (), m_fndecl (fndecl), m_id (NULL), m_oparms (), m_new_decls
> (),
> + m_new_types (), m_replacements (), m_removed_decls (), m_removed_map (),
> m_method2func (false)
> {
> common_initialization (fndecl, NULL, NULL);
> @@ -1174,9 +1275,10 @@ ipa_param_body_adjustments
> copy_body_data *id, tree *vars,
> vec<ipa_replace_map *, va_gc> *tree_map)
> : m_adj_params (adjustments->m_adj_params), m_adjustments (adjustments),
> - m_reset_debug_decls (), m_split_modifications_p (false), m_fndecl
> (fndecl),
> - m_id (id), m_oparms (), m_new_decls (), m_new_types (), m_replacements
> (),
> - m_removed_decls (), m_removed_map (), m_method2func (false)
> + m_reset_debug_decls (), m_split_modifications_p (false), m_dead_stmts (),
> + m_dead_ssas (),m_fndecl (fndecl), m_id (id), m_oparms (), m_new_decls (),
> + m_new_types (), m_replacements (), m_removed_decls (), m_removed_map (),
> + m_method2func (false)
> {
> common_initialization (old_fndecl, vars, tree_map);
> }
> @@ -1623,8 +1725,9 @@ ipa_param_body_adjustments::modify_call_stmt (gcall
> **stmt_p,
> && TREE_CODE (t) != IMAGPART_EXPR
> && TREE_CODE (t) != REALPART_EXPR);
>
> - /* The follow-up patch will check whether t needs to be removed, that's
> - why this condition is in the loop. */
> + if (TREE_CODE (t) == SSA_NAME
> + && m_dead_ssas.contains (t))
> + recreate = true;
>
> if (!m_split_modifications_p)
> continue;
> @@ -1762,10 +1865,19 @@ ipa_param_body_adjustments::modify_call_stmt (gcall
> **stmt_p,
> else
> {
> tree t = gimple_call_arg (stmt, i);
> - modify_expression (&t, true);
> - vargs.safe_push (t);
> - index_map.safe_push (new_arg_idx);
> - new_arg_idx++;
> + if (TREE_CODE (t) == SSA_NAME
> + && m_dead_ssas.contains (t))
> + {
> + always_copy_delta--;
> + index_map.safe_push (-1);
> + }
> + else
> + {
> + modify_expression (&t, true);
> + vargs.safe_push (t);
> + index_map.safe_push (new_arg_idx);
> + new_arg_idx++;
> + }
> }
> }
>
> diff --git a/gcc/ipa-param-manipulation.h b/gcc/ipa-param-manipulation.h
> index fd0df7b299c..17e20aff3ca 100644
> --- a/gcc/ipa-param-manipulation.h
> +++ b/gcc/ipa-param-manipulation.h
> @@ -342,6 +342,12 @@ public:
> /* Set to true if there are any IPA_PARAM_OP_SPLIT adjustments among stored
> adjustments. */
> bool m_split_modifications_p;
> +
> + /* Sets of statements and SSA_NAMEs that only manipulate data from
> parameters
> + removed because they are not necessary. */
> + hash_set<gimple *> m_dead_stmts;
> + hash_set<tree> m_dead_ssas;
> +
> private:
> void common_initialization (tree old_fndecl, tree *vars,
> vec<ipa_replace_map *, va_gc> *tree_map);
> diff --git a/gcc/testsuite/g++.dg/ipa/ipa-sra-4.C
> b/gcc/testsuite/g++.dg/ipa/ipa-sra-4.C
> new file mode 100644
> index 00000000000..56d59f9fd9a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ipa/ipa-sra-4.C
> @@ -0,0 +1,37 @@
> +/* { dg-do compile { target c++11 } } */
> +/* { dg-options "-O2 -fipa-sra" } */
> +
> +void __throw_bad_alloc() __attribute__((__noreturn__));
> +void __throw_bad_array_new_length();
> +template <typename> class allocator {};
> +template <typename> struct allocator_traits;
> +int *allocate___trans_tmp_2;
> +template <typename _Tp> struct allocator_traits<allocator<_Tp>> {
> + using allocator_type = allocator<_Tp>;
> + using pointer = _Tp *;
> + using size_type = long;
> + static pointer allocate(allocator_type &, size_type __n) {
> + long __trans_tmp_3 = __n;
> + if (__builtin_expect(__trans_tmp_3, false))
> + if (__trans_tmp_3)
> + __throw_bad_array_new_length();
> + operator new(sizeof(int));
> + return allocate___trans_tmp_2;
> + }
> +};
> +class throw_allocator_base {
> + allocator<int> _M_allocator;
> +public:
> + int *allocate(long __n) {
> + if (__n)
> + __throw_bad_alloc();
> + int *a = allocator_traits<allocator<int>>::allocate(_M_allocator, __n);
> + return a;
> + }
> +};
> +template <typename Alloc> void check_allocate_max_size() {
> + Alloc a;
> + long __trans_tmp_1 = 0;
> + a.allocate(__trans_tmp_1 + 1);
> +}
> +int main() { check_allocate_max_size<throw_allocator_base>(); }
> diff --git a/gcc/testsuite/gcc.dg/ipa/ipa-sra-23.c
> b/gcc/testsuite/gcc.dg/ipa/ipa-sra-23.c
> new file mode 100644
> index 00000000000..f438b509614
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/ipa-sra-23.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +extern int g;
> +
> +static int __attribute__((noinline))
> +bar (int i, int j)
> +{
> + return 2*g + i;
> +}
> +
> +static int __attribute__((noinline))
> +foo (int i, int j)
> +{
> + if (i > 5)
> + j = 22;
> + return bar (i, j) + 1;
> +}
> +
> +int
> +entry (int l, int k)
> +{
> + return foo (l, k);
> +}
> diff --git a/gcc/testsuite/gcc.dg/ipa/ipa-sra-24.c
> b/gcc/testsuite/gcc.dg/ipa/ipa-sra-24.c
> new file mode 100644
> index 00000000000..7b5bf0825fc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/ipa-sra-24.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -Wmaybe-uninitialized -Werror" } */
> +
> +int *ttmp_1;
> +_Bool pt_ins_tipdo, pq_ins_apd, pq_ins_tt2;
> +int gtrphdt;
> +
> +void pl_ins(int, _Bool, _Bool);
> +inline void pt_ins(int *, _Bool apdo) {
> + int list = *ttmp_1;
> + pl_ins(list, apdo, pt_ins_tipdo);
> +}
> +void pq_ins(int *t) {
> + if (pq_ins_tt2)
> + pt_ins(t, pq_ins_apd);
> +}
> +int gtr_post_hd() {
> + pq_ins(>rphdt);
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/ipa/pr93385.c
> b/gcc/testsuite/gcc.dg/ipa/pr93385.c
> new file mode 100644
> index 00000000000..6d1d0d7cd27
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/pr93385.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-dce -fno-ipa-cp -fno-tree-dce" } */
> +
> +char a, b;
> +
> +#ifdef __SIZEOF_INT128__
> +#define T unsigned __int128
> +#else
> +#define T unsigned
> +#endif
> +
> +static inline int
> +c (T d)
> +{
> + char e = 0;
> + d %= (unsigned) d;
> + e -= 0;
> + __builtin_strncpy (&a, &e, 1);
> + return e + b;
> +}
> +
> +int
> +main (void)
> +{
> + c (~0);
> + return 0;
> +}
> diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
> index e2fb6be681c..cad11eeae17 100644
> --- a/gcc/tree-inline.c
> +++ b/gcc/tree-inline.c
> @@ -1504,6 +1504,11 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
> : !opt_for_fn (id->dst_fn, flag_var_tracking_assignments)))
> return NULL;
>
> + if (!is_gimple_debug (stmt)
> + && id->param_body_adjs
> + && id->param_body_adjs->m_dead_stmts.contains (stmt))
> + return NULL;
> +
> /* Begin by recognizing trees that we'll completely rewrite for the
> inlining context. Our output for these trees is completely
> different from our input (e.g. RETURN_EXPR is deleted and morphs
> @@ -1768,10 +1773,15 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
>
> if (gimple_debug_bind_p (stmt))
> {
> + tree value;
> + if (id->param_body_adjs
> + && id->param_body_adjs->m_dead_stmts.contains (stmt))
> + value = NULL_TREE;
> + else
> + value = gimple_debug_bind_get_value (stmt);
> gdebug *copy
> = gimple_build_debug_bind (gimple_debug_bind_get_var (stmt),
> - gimple_debug_bind_get_value (stmt),
> - stmt);
> + value, stmt);
> if (id->reset_location)
> gimple_set_location (copy, input_location);
> id->debug_stmts.safe_push (copy);
> @@ -2650,7 +2660,9 @@ copy_phis_for_bb (basic_block bb, copy_body_data *id)
> phi = si.phi ();
> res = PHI_RESULT (phi);
> new_res = res;
> - if (!virtual_operand_p (res))
> + if (!virtual_operand_p (res)
> + && (!id->param_body_adjs
> + || !id->param_body_adjs->m_dead_stmts.contains (phi)))
> {
> walk_tree (&new_res, copy_tree_body_r, id, NULL);
> if (EDGE_COUNT (new_bb->preds) == 0)
> --
> 2.31.1
>
