ipa-sra: Improve debug info for removed parameters (PR 93385)

  Hi,

in spring I added code eliminating any statements using parameters
removed by IPA passes (to fix PR 93385).  That patch fixed issues such
as divisions by zero that such code could perform but it only reset
all affected debug bind statements, this one updates them with
expressions which can allow the debugger to print the removed value -
see the added test-case for an example.

Even though I originally did not want to create DEBUG_EXPR_DECLs for
intermediate values, I ended up doing so, because otherwise the code
started creating statements like

   # DEBUG __aD.198693 => &MEM[(const struct _Alloc_nodeD.171110 *)D#195]._M_tD.184726->_M_implD.171154

which not only is a bit scary but also gimple-fold ICEs on
it. Therefore I decided they are probably quite necessary.

The patch simply notes each removed SSA name present in a debug
statement and then works from it backwards, looking if it can
reconstruct the expression it represents (which can fail if a
non-degenerate PHI node is in the way).  If it can, it populates two
hash maps with those expressions so that 1) removed assignments are
replaced with a debug bind defining a new intermediate debug_decl_expr
and 2) existing debug binds that refer to SSA names that are bing
removed now refer to corresponding debug_decl_exprs.

If a removed parameter is passed to another function, the debugging
information still cannot describe its value there - see the xfailed
test in the testcase.  I sort of know what needs to be done but that
needs a little bit more of IPA infrastructure on top of this patch and
so I would like to get this patch reviewed first.

Bootstrapped and tested on x86_64-linux, i686-linux and (long time
ago) on aarch64-linux.  Also LTO-bootstrapped and on x86_64-linux.

Perhaps it is good to go to trunk?

Thanks,

Martin

gcc/ChangeLog:

2021-03-29  Martin Jambor  <mjambor@suse.cz>

	PR ipa/93385
	* ipa-param-manipulation.h (class ipa_param_body_adjustments): New
	members remap_with_debug_expressions, m_dead_ssa_debug_equiv,
	m_dead_stmt_debug_equiv and prepare_debug_expressions.  Added
	parameter to mark_dead_statements.
	* ipa-param-manipulation.c: Include tree-phinodes.h and cfgexpand.h.
	(ipa_param_body_adjustments::mark_dead_statements): New parameter
	debugstack, push into it all SSA names used in debug statements,
	produce m_dead_ssa_debug_equiv mapping for the removed param.
	(replace_with_mapped_expr): New function.
	(ipa_param_body_adjustments::remap_with_debug_expressions): Likewise.
	(ipa_param_body_adjustments::prepare_debug_expressions): Likewise.
	(ipa_param_body_adjustments::common_initialization): Gather and
	procecc SSA which will be removed but are in debug statements. Simplify.
	(ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
	new members.
	* tree-inline.c (remap_gimple_stmt): Create a debug bind when possible
	when avoiding a copy of an unnecessary statement.  Remap removed SSA
	names in existing debug statements.
	(tree_function_versioning): Do not create DEBUG_EXPR_DECL for removed
	parameters if we have already done so.

gcc/testsuite/ChangeLog:

2021-03-29  Martin Jambor  <mjambor@suse.cz>

	PR ipa/93385
	* gcc.dg/guality/ipa-sra-1.c: New test.
---
 gcc/ipa-param-manipulation.c             | 280 ++++++++++++++++++-----
 gcc/ipa-param-manipulation.h             |  12 +-
 gcc/testsuite/gcc.dg/guality/ipa-sra-1.c |  45 ++++
 gcc/tree-inline.c                        |  45 ++--
 4 files changed, 305 insertions(+), 77 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
  

Hello,

I'd like to ping this patch.

Thanks,

Martin


On Wed, Oct 13 2021, Martin Jambor wrote:
> Hi,
>
> in spring I added code eliminating any statements using parameters
> removed by IPA passes (to fix PR 93385).  That patch fixed issues such
> as divisions by zero that such code could perform but it only reset
> all affected debug bind statements, this one updates them with
> expressions which can allow the debugger to print the removed value -
> see the added test-case for an example.
>
> Even though I originally did not want to create DEBUG_EXPR_DECLs for
> intermediate values, I ended up doing so, because otherwise the code
> started creating statements like
>
>    # DEBUG __aD.198693 => &MEM[(const struct _Alloc_nodeD.171110 *)D#195]._M_tD.184726->_M_implD.171154
>
> which not only is a bit scary but also gimple-fold ICEs on
> it. Therefore I decided they are probably quite necessary.
>
> The patch simply notes each removed SSA name present in a debug
> statement and then works from it backwards, looking if it can
> reconstruct the expression it represents (which can fail if a
> non-degenerate PHI node is in the way).  If it can, it populates two
> hash maps with those expressions so that 1) removed assignments are
> replaced with a debug bind defining a new intermediate debug_decl_expr
> and 2) existing debug binds that refer to SSA names that are bing
> removed now refer to corresponding debug_decl_exprs.
>
> If a removed parameter is passed to another function, the debugging
> information still cannot describe its value there - see the xfailed
> test in the testcase.  I sort of know what needs to be done but that
> needs a little bit more of IPA infrastructure on top of this patch and
> so I would like to get this patch reviewed first.
>
> Bootstrapped and tested on x86_64-linux, i686-linux and (long time
> ago) on aarch64-linux.  Also LTO-bootstrapped and on x86_64-linux.
>
> Perhaps it is good to go to trunk?
>
> Thanks,
>
> Martin
>
> gcc/ChangeLog:
>
> 2021-03-29  Martin Jambor  <mjambor@suse.cz>
>
> 	PR ipa/93385
> 	* ipa-param-manipulation.h (class ipa_param_body_adjustments): New
> 	members remap_with_debug_expressions, m_dead_ssa_debug_equiv,
> 	m_dead_stmt_debug_equiv and prepare_debug_expressions.  Added
> 	parameter to mark_dead_statements.
> 	* ipa-param-manipulation.c: Include tree-phinodes.h and cfgexpand.h.
> 	(ipa_param_body_adjustments::mark_dead_statements): New parameter
> 	debugstack, push into it all SSA names used in debug statements,
> 	produce m_dead_ssa_debug_equiv mapping for the removed param.
> 	(replace_with_mapped_expr): New function.
> 	(ipa_param_body_adjustments::remap_with_debug_expressions): Likewise.
> 	(ipa_param_body_adjustments::prepare_debug_expressions): Likewise.
> 	(ipa_param_body_adjustments::common_initialization): Gather and
> 	procecc SSA which will be removed but are in debug statements. Simplify.
> 	(ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
> 	new members.
> 	* tree-inline.c (remap_gimple_stmt): Create a debug bind when possible
> 	when avoiding a copy of an unnecessary statement.  Remap removed SSA
> 	names in existing debug statements.
> 	(tree_function_versioning): Do not create DEBUG_EXPR_DECL for removed
> 	parameters if we have already done so.
>
> gcc/testsuite/ChangeLog:
>
> 2021-03-29  Martin Jambor  <mjambor@suse.cz>
>
> 	PR ipa/93385
> 	* gcc.dg/guality/ipa-sra-1.c: New test.
> ---
>  gcc/ipa-param-manipulation.c             | 280 ++++++++++++++++++-----
>  gcc/ipa-param-manipulation.h             |  12 +-
>  gcc/testsuite/gcc.dg/guality/ipa-sra-1.c |  45 ++++
>  gcc/tree-inline.c                        |  45 ++--
>  4 files changed, 305 insertions(+), 77 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
>
> diff --git a/gcc/ipa-param-manipulation.c b/gcc/ipa-param-manipulation.c
> index 26b02d7aa95..c84d669521c 100644
> --- a/gcc/ipa-param-manipulation.c
> +++ b/gcc/ipa-param-manipulation.c
> @@ -43,6 +43,8 @@ along with GCC; see the file COPYING3.  If not see
>  #include "alloc-pool.h"
>  #include "symbol-summary.h"
>  #include "symtab-clones.h"
> +#include "tree-phinodes.h"
> +#include "cfgexpand.h"
>  
>  
>  /* Actual prefixes of different newly synthetized parameters.  Keep in sync
> @@ -972,10 +974,12 @@ ipa_param_body_adjustments::carry_over_param (tree t)
>  
>  /* 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.  */
> +   remaining uses of a removed parameter on.  Push all removed SSA names that
> +   are used within debug statements to DEBUGSTACK.  */
>  
>  void
> -ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> +ipa_param_body_adjustments::mark_dead_statements (tree dead_param,
> +						  vec<tree> *debugstack)
>  {
>    /* Current IPA analyses which remove unused parameters never remove a
>       non-gimple register ones which have any use except as parameters in other
> @@ -987,6 +991,7 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
>      return;
>  
>    auto_vec<tree, 4> stack;
> +  hash_set<tree> used_in_debug;
>    m_dead_ssas.add (parm_ddef);
>    stack.safe_push (parm_ddef);
>    while (!stack.is_empty ())
> @@ -1014,6 +1019,11 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
>  	    {
>  	      m_dead_stmts.add (stmt);
>  	      gcc_assert (gimple_debug_bind_p (stmt));
> +	      if (!used_in_debug.contains (t))
> +		{
> +		  used_in_debug.add (t);
> +		  debugstack->safe_push (t);
> +		}
>  	    }
>  	  else if (gimple_code (stmt) == GIMPLE_PHI)
>  	    {
> @@ -1046,6 +1056,149 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
>  	    gcc_unreachable ();
>  	}
>      }
> +
> +  if (!MAY_HAVE_DEBUG_STMTS)
> +    {
> +      gcc_assert (debugstack->is_empty ());
> +      return;
> +    }
> +
> +  tree dp_ddecl = make_node (DEBUG_EXPR_DECL);
> +  DECL_ARTIFICIAL (dp_ddecl) = 1;
> +  TREE_TYPE (dp_ddecl) = TREE_TYPE (dead_param);
> +  SET_DECL_MODE (dp_ddecl, DECL_MODE (dead_param));
> +  m_dead_ssa_debug_equiv.put (parm_ddef, dp_ddecl);
> +}
> +
> +/* Callback to walk_tree.  If REMAP is an SSA_NAME that is present in hash_map
> +   passed in DATA, replace it with unshared version of what it was mapped
> +   to.  */
> +
> +static tree
> +replace_with_mapped_expr (tree *remap, int *walk_subtrees, void *data)
> +{
> +  if (TYPE_P (*remap))
> +    {
> +      *walk_subtrees = 0;
> +      return 0;
> +    }
> +  if (TREE_CODE (*remap) != SSA_NAME)
> +    return 0;
> +
> +  *walk_subtrees = 0;
> +
> +  hash_map<tree, tree> *equivs = (hash_map<tree, tree> *) data;
> +  if (tree *p = equivs->get (*remap))
> +    *remap = unshare_expr (*p);
> +  return 0;
> +}
> +
> +/* Replace all occurances of SSAs in m_dead_ssa_debug_equiv in t with what they
> +   are mapped to.  */
> +
> +void
> +ipa_param_body_adjustments::remap_with_debug_expressions (tree *t)
> +{
> +  /* If *t is an SSA_NAME which should have its debug statements reset, it is
> +     mapped to NULL in the hash_map.  We need to handle that case separately or
> +     otherwise the walker would segfault.  No expression that is more
> +     complicated than that can have its operands mapped to NULL.  */
> +  if (TREE_CODE (*t) == SSA_NAME)
> +    {
> +      if (tree *p = m_dead_ssa_debug_equiv.get (*t))
> +	*t = *p;
> +    }
> +  else
> +    walk_tree (t, replace_with_mapped_expr, &m_dead_ssa_debug_equiv, NULL);
> +}
> +
> +/* For an SSA_NAME DEAD_SSA which is about to be DCEd because it is based on a
> +   useless parameter, prepare an expression that should represent it in
> +   debug_binds in the cloned function and add a mapping from DEAD_SSA to
> +   m_dead_ssa_debug_equiv.  That mapping is to NULL when the associated
> +   debug_statement has to be reset instead.  In such case return false,
> +   ottherwise return true.  If DEAD_SSA comes from a basic block which is not
> +   about to be copied, ignore it and return true.  */
> +
> +bool
> +ipa_param_body_adjustments::prepare_debug_expressions (tree dead_ssa)
> +{
> +  gcc_checking_assert (m_dead_ssas.contains (dead_ssa));
> +  if (tree *d = m_dead_ssa_debug_equiv.get (dead_ssa))
> +    return (*d != NULL_TREE);
> +
> +  gcc_assert (!SSA_NAME_IS_DEFAULT_DEF (dead_ssa));
> +  gimple *def = SSA_NAME_DEF_STMT (dead_ssa);
> +  if (m_id->blocks_to_copy
> +      && !bitmap_bit_p (m_id->blocks_to_copy, gimple_bb (def)->index))
> +    return true;
> +
> +  if (gimple_code (def) == GIMPLE_PHI)
> +    {
> +      /* In theory, we could ignore all SSAs coming from BBs not in
> +	 m_id->blocks_to_copy but at the time of the writing this code that
> +	 should never really be the case because only fnsplit uses that bitmap,
> +	 so don't bother.  */
> +      tree value = degenerate_phi_result (as_a <gphi *> (def));
> +      if (!value
> +	  || (m_dead_ssas.contains (value)
> +	      && !prepare_debug_expressions (value)))
> +	{
> +	  m_dead_ssa_debug_equiv.put (dead_ssa, NULL_TREE);
> +	  return false;
> +	}
> +
> +      gcc_assert (TREE_CODE (value) == SSA_NAME);
> +      tree *d = m_dead_ssa_debug_equiv.get (value);
> +      m_dead_ssa_debug_equiv.put (dead_ssa, *d);
> +      return true;
> +    }
> +
> +  bool lost = false;
> +  use_operand_p use_p;
> +  ssa_op_iter oi;
> +  FOR_EACH_PHI_OR_STMT_USE (use_p, def, oi, SSA_OP_USE)
> +    {
> +      tree use = USE_FROM_PTR (use_p);
> +      if (m_dead_ssas.contains (use)
> +	  && !prepare_debug_expressions (use))
> +	{
> +	  lost = true;
> +	  break;
> +	}
> +    }
> +
> +  if (lost)
> +    {
> +      m_dead_ssa_debug_equiv.put (dead_ssa, NULL_TREE);
> +      return false;
> +    }
> +
> +  if (is_gimple_assign (def))
> +    {
> +      gcc_assert (!gimple_clobber_p (def));
> +      if (gimple_assign_copy_p (def)
> +	  && TREE_CODE (gimple_assign_rhs1 (def)) == SSA_NAME)
> +	{
> +	  tree *d = m_dead_ssa_debug_equiv.get (gimple_assign_rhs1 (def));
> +	  m_dead_ssa_debug_equiv.put (dead_ssa, *d);
> +	  return (*d != NULL_TREE);
> +	}
> +
> +      tree val = gimple_assign_rhs_to_tree (def);
> +      SET_EXPR_LOCATION (val, UNKNOWN_LOCATION);
> +      remap_with_debug_expressions (&val);
> +
> +      tree vexpr = make_node (DEBUG_EXPR_DECL);
> +      DECL_ARTIFICIAL (vexpr) = 1;
> +      TREE_TYPE (vexpr) = TREE_TYPE (val);
> +      SET_DECL_MODE (vexpr, TYPE_MODE (TREE_TYPE (val)));
> +      m_dead_stmt_debug_equiv.put (def, val);
> +      m_dead_ssa_debug_equiv.put (dead_ssa, vexpr);
> +      return true;
> +    }
> +  else
> +    gcc_unreachable ();
>  }
>  
>  /* Common initialization performed by all ipa_param_body_adjustments
> @@ -1137,65 +1290,21 @@ ipa_param_body_adjustments::common_initialization (tree old_fndecl,
>  	gcc_unreachable ();
>      }
>  
> -
> -  /* As part of body modifications, we will also have to replace remaining uses
> -     of remaining uses of removed PARM_DECLs (which do not however use the
> -     initial value) with their VAR_DECL copies.
> -
> -     We do this differently with and without m_id.  With m_id, we rely on its
> -     mapping and create a replacement straight away.  Without it, we have our
> -     own mechanism for which we have to populate m_removed_decls vector.  Just
> -     don't mix them, that is why you should not call
> -     replace_removed_params_ssa_names or perform_cfun_body_modifications when
> -     you construct with ID not equal to NULL.  */
> -
> -  unsigned op_len = m_oparms.length ();
> -  for (unsigned i = 0; i < op_len; i++)
> -    if (!kept[i])
> -      {
> -	if (m_id)
> -	  {
> -	    if (!m_id->decl_map->get (m_oparms[i]))
> -	      {
> -		tree var = copy_decl_to_var (m_oparms[i], m_id);
> -		insert_decl_map (m_id, m_oparms[i], var);
> -		/* 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
> -	  {
> -	    m_removed_decls.safe_push (m_oparms[i]);
> -	    m_removed_map.put (m_oparms[i], m_removed_decls.length () - 1);
> -	  }
> -      }
> -
> -  if (!MAY_HAVE_DEBUG_STMTS)
> -    return;
> -
> -  /* Finally, when generating debug info, we fill vector m_reset_debug_decls
> -    with removed parameters declarations.  We do this in order to re-map their
> -    debug bind statements and create debug decls for them.  */
> -
>    if (tree_map)
>      {
> -      /* Do not output debuginfo for parameter declarations as if they vanished
> -	 when they were in fact replaced by a constant.  */
> +      /* Do not treat parameters which were replaced with a constant as
> +	 completely vanished.  */
>        auto_vec <int, 16> index_mapping;
>        bool need_remap = false;
> -      clone_info *info = clone_info::get (m_id->src_node);
>  
> -      if (m_id && info && info->param_adjustments)
> +      if (m_id)
>  	{
> -	  ipa_param_adjustments *prev_adjustments = info->param_adjustments;
> -	  prev_adjustments->get_updated_indices (&index_mapping);
> -	  need_remap = true;
> +	  clone_info *cinfo = clone_info::get (m_id->src_node);
> +	  if (cinfo && cinfo->param_adjustments)
> +	    {
> +	      cinfo->param_adjustments->get_updated_indices (&index_mapping);
> +	      need_remap = true;
> +	    }
>  	}
>  
>        for (unsigned i = 0; i < tree_map->length (); i++)
> @@ -1208,9 +1317,52 @@ ipa_param_body_adjustments::common_initialization (tree old_fndecl,
>  	}
>      }
>  
> +  /* As part of body modifications, we will also have to replace remaining uses
> +     of remaining uses of removed PARM_DECLs (which do not however use the
> +     initial value) with their VAR_DECL copies.
> +
> +     We do this differently with and without m_id.  With m_id, we rely on its
> +     mapping and create a replacement straight away.  Without it, we have our
> +     own mechanism for which we have to populate m_removed_decls vector.  Just
> +     don't mix them, that is why you should not call
> +     replace_removed_params_ssa_names or perform_cfun_body_modifications when
> +     you construct with ID not equal to NULL.  */
> +
> +  auto_vec<tree, 8> ssas_to_process_debug;
> +  unsigned op_len = m_oparms.length ();
>    for (unsigned i = 0; i < op_len; i++)
> -    if (!kept[i] && is_gimple_reg (m_oparms[i]))
> -      m_reset_debug_decls.safe_push (m_oparms[i]);
> +    if (!kept[i])
> +      {
> +	if (m_id)
> +	  {
> +	    gcc_assert (!m_id->decl_map->get (m_oparms[i]));
> +	    tree var = copy_decl_to_var (m_oparms[i], m_id);
> +	    insert_decl_map (m_id, m_oparms[i], var);
> +	    /* 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], &ssas_to_process_debug);
> +	    if (MAY_HAVE_DEBUG_STMTS
> +		&& is_gimple_reg (m_oparms[i]))
> +	      m_reset_debug_decls.safe_push (m_oparms[i]);
> +	  }
> +	else
> +	  {
> +	    m_removed_decls.safe_push (m_oparms[i]);
> +	    m_removed_map.put (m_oparms[i], m_removed_decls.length () - 1);
> +	    if (MAY_HAVE_DEBUG_STMTS
> +		&& !kept[i]
> +		&& is_gimple_reg (m_oparms[i]))
> +	      m_reset_debug_decls.safe_push (m_oparms[i]);
> +	  }
> +      }
> +
> +  while (!ssas_to_process_debug.is_empty ())
> +    prepare_debug_expressions (ssas_to_process_debug.pop ());
>  }
>  
>  /* Constructor of ipa_param_body_adjustments from a simple list of
> @@ -1224,9 +1376,9 @@ ipa_param_body_adjustments
>  			      tree fndecl)
>    : m_adj_params (adj_params), m_adjustments (NULL), 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)
> +    m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (), 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);
>  }
> @@ -1241,7 +1393,8 @@ ipa_param_body_adjustments
>  			      tree fndecl)
>    : m_adj_params (adjustments->m_adj_params), m_adjustments (adjustments),
>      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_dead_ssas (), m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (),
> +    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)
>  {
> @@ -1264,8 +1417,9 @@ ipa_param_body_adjustments
>  			      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_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_dead_ssas (), m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (),
> +    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);
> diff --git a/gcc/ipa-param-manipulation.h b/gcc/ipa-param-manipulation.h
> index afcbc09bf33..9440cbfc56c 100644
> --- a/gcc/ipa-param-manipulation.h
> +++ b/gcc/ipa-param-manipulation.h
> @@ -328,6 +328,9 @@ public:
>  			   gimple *orig_stmt);
>    /* Return the new chain of parameters.  */
>    tree get_new_param_chain ();
> +  /* Replace all occurances of SSAs in m_dead_ssa_debug_equiv in t with what
> +     they are mapped to.  */
> +  void remap_with_debug_expressions (tree *t);
>  
>    /* Pointers to data structures defining how the function should be
>       modified.  */
> @@ -348,6 +351,12 @@ public:
>    hash_set<gimple *> m_dead_stmts;
>    hash_set<tree> m_dead_ssas;
>  
> +  /* Mapping from DCEd SSAs to what their potential debug_binds should be.  */
> +  hash_map<tree, tree> m_dead_ssa_debug_equiv;
> +  /* Mapping from DCEd statements to debug expressions that will be placed on
> +     the RHS of debug statement that will replace this one.  */
> +  hash_map<gimple *, tree> m_dead_stmt_debug_equiv;
> +
>  private:
>    void common_initialization (tree old_fndecl, tree *vars,
>  			      vec<ipa_replace_map *, va_gc> *tree_map);
> @@ -361,7 +370,8 @@ private:
>    bool modify_call_stmt (gcall **stmt_p, gimple *orig_stmt);
>    bool modify_cfun_body ();
>    void reset_debug_stmts ();
> -  void mark_dead_statements (tree dead_param);
> +  void mark_dead_statements (tree dead_param, vec<tree> *debugstack);
> +  bool prepare_debug_expressions (tree dead_ssa);
>  
>    /* Declaration of the function that is being transformed.  */
>  
> diff --git a/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c b/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
> new file mode 100644
> index 00000000000..5434b3d7665
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
> @@ -0,0 +1,45 @@
> +/* { dg-do run } */
> +/* { dg-options "-g -fno-ipa-icf" } */
> +
> +
> +void __attribute__((noipa))
> +use (int x)
> +{
> +  asm volatile ("" : : "r" (x) : "memory");
> +}
> +
> +static int __attribute__((noinline))
> +bar (int i, int k)
> +{
> +  asm ("" : "+r" (i));
> +  use (i);		/* { dg-final { gdb-test . "k" "3" { xfail *-*-* } } } */
> +  return 6;
> +}
> +
> +volatile int v;
> +
> +static int __attribute__((noinline))
> +foo (int i, int k)
> +{
> +  int r;
> +  v = 9;
> +  k = (k + 14)/k;
> +  r = bar (i, k);		/* { dg-final { gdb-test . "k" "3" } } */
> +  return r;
> +}
> +
> +volatile int v;
> +
> +int __attribute__((noipa))
> +get_val1 (void)  {return 20;}
> +int __attribute__((noipa))
> +get_val2 (void)  {return 7;}
> +
> +int
> +main (void)
> +{
> +  int k = get_val2 ();
> +  int r = foo (get_val1 (), k);
> +  v = r + k;   /* k has to live accross the call or all is probably lost  */
> +  return 0;
> +}
> diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
> index e292a144967..6cf4a0e9f36 100644
> --- a/gcc/tree-inline.c
> +++ b/gcc/tree-inline.c
> @@ -1529,7 +1529,21 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
>    if (!is_gimple_debug (stmt)
>        && id->param_body_adjs
>        && id->param_body_adjs->m_dead_stmts.contains (stmt))
> -    return NULL;
> +    {
> +      tree *dval = id->param_body_adjs->m_dead_stmt_debug_equiv.get (stmt);
> +      if (!dval)
> +	return NULL;
> +
> +      gcc_assert (is_gimple_assign (stmt));
> +      tree lhs = gimple_assign_lhs (stmt);
> +      tree *dvar = id->param_body_adjs->m_dead_ssa_debug_equiv.get (lhs);
> +      gdebug *bind = gimple_build_debug_bind (*dvar, *dval, stmt);
> +      if (id->reset_location)
> +	gimple_set_location (bind, input_location);
> +      id->debug_stmts.safe_push (bind);
> +      gimple_seq_add_stmt (&stmts, bind);
> +      return stmts;
> +    }
>  
>    /* Begin by recognizing trees that we'll completely rewrite for the
>       inlining context.  Our output for these trees is completely
> @@ -1807,15 +1821,13 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
>  
>        if (gimple_debug_bind_p (stmt))
>  	{
> -	  tree value;
> +	  tree var = gimple_debug_bind_get_var (stmt);
> +	  tree value = gimple_debug_bind_get_value (stmt);
>  	  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),
> -				       value, stmt);
> +	    id->param_body_adjs->remap_with_debug_expressions (&value);
> +
> +	  gdebug *copy = gimple_build_debug_bind (var, value, stmt);
>  	  if (id->reset_location)
>  	    gimple_set_location (copy, input_location);
>  	  id->debug_stmts.safe_push (copy);
> @@ -6446,7 +6458,6 @@ tree_function_versioning (tree old_decl, tree new_decl,
>  	     in the debug info that var (whole DECL_ORIGIN is the parm
>  	     PARM_DECL) is optimized away, but could be looked up at the
>  	     call site as value of D#X there.  */
> -	  tree vexpr;
>  	  gimple_stmt_iterator cgsi
>  	    = gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
>  	  gimple *def_temp;
> @@ -6454,17 +6465,25 @@ tree_function_versioning (tree old_decl, tree new_decl,
>  	  i = vec_safe_length (*debug_args);
>  	  do
>  	    {
> +	      tree vexpr = NULL_TREE;
>  	      i -= 2;
>  	      while (var != NULL_TREE
>  		     && DECL_ABSTRACT_ORIGIN (var) != (**debug_args)[i])
>  		var = TREE_CHAIN (var);
>  	      if (var == NULL_TREE)
>  		break;
> -	      vexpr = make_node (DEBUG_EXPR_DECL);
>  	      tree parm = (**debug_args)[i];
> -	      DECL_ARTIFICIAL (vexpr) = 1;
> -	      TREE_TYPE (vexpr) = TREE_TYPE (parm);
> -	      SET_DECL_MODE (vexpr, DECL_MODE (parm));
> +	      if (tree parm_ddef = ssa_default_def (id.src_cfun, parm))
> +		if (tree *d
> +		    = param_body_adjs->m_dead_ssa_debug_equiv.get (parm_ddef))
> +		  vexpr = *d;
> +	      if (!vexpr)
> +		{
> +		  vexpr = make_node (DEBUG_EXPR_DECL);
> +		  DECL_ARTIFICIAL (vexpr) = 1;
> +		  TREE_TYPE (vexpr) = TREE_TYPE (parm);
> +		  SET_DECL_MODE (vexpr, DECL_MODE (parm));
> +		}
>  	      def_temp = gimple_build_debug_bind (var, vexpr, NULL);
>  	      gsi_insert_before (&cgsi, def_temp, GSI_NEW_STMT);
>  	      def_temp = gimple_build_debug_source_bind (vexpr, parm, NULL);
> -- 
> 2.33.0
  

On Mon, 1 Nov 2021, Martin Jambor wrote:

> Hello,
> 
> I'd like to ping this patch.
> 
> Thanks,
> 
> Martin
> 
> 
> On Wed, Oct 13 2021, Martin Jambor wrote:
> > Hi,
> >
> > in spring I added code eliminating any statements using parameters
> > removed by IPA passes (to fix PR 93385).  That patch fixed issues such
> > as divisions by zero that such code could perform but it only reset
> > all affected debug bind statements, this one updates them with
> > expressions which can allow the debugger to print the removed value -
> > see the added test-case for an example.
> >
> > Even though I originally did not want to create DEBUG_EXPR_DECLs for
> > intermediate values, I ended up doing so, because otherwise the code
> > started creating statements like
> >
> >    # DEBUG __aD.198693 => &MEM[(const struct _Alloc_nodeD.171110 *)D#195]._M_tD.184726->_M_implD.171154
> >
> > which not only is a bit scary but also gimple-fold ICEs on
> > it. Therefore I decided they are probably quite necessary.
> >
> > The patch simply notes each removed SSA name present in a debug
> > statement and then works from it backwards, looking if it can
> > reconstruct the expression it represents (which can fail if a
> > non-degenerate PHI node is in the way).  If it can, it populates two
> > hash maps with those expressions so that 1) removed assignments are
> > replaced with a debug bind defining a new intermediate debug_decl_expr
> > and 2) existing debug binds that refer to SSA names that are bing
> > removed now refer to corresponding debug_decl_exprs.
> >
> > If a removed parameter is passed to another function, the debugging
> > information still cannot describe its value there - see the xfailed
> > test in the testcase.  I sort of know what needs to be done but that
> > needs a little bit more of IPA infrastructure on top of this patch and
> > so I would like to get this patch reviewed first.
> >
> > Bootstrapped and tested on x86_64-linux, i686-linux and (long time
> > ago) on aarch64-linux.  Also LTO-bootstrapped and on x86_64-linux.
> >
> > Perhaps it is good to go to trunk?

I think the patch is OK for trunk.  It would be nice to common the

+      tree vexpr = make_node (DEBUG_EXPR_DECL);
+      DECL_ARTIFICIAL (vexpr) = 1;
+      TREE_TYPE (vexpr) = TREE_TYPE (val);
+      SET_DECL_MODE (vexpr, TYPE_MODE (TREE_TYPE (val)));

blob that exists all over the GCC code base with a new
build_debug_expr_decl (tree type) (next to tree.c:build_decl).

Thanks,
Richard.

> > Thanks,
> >
> > Martin
> >
> > gcc/ChangeLog:
> >
> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
> >
> > 	PR ipa/93385
> > 	* ipa-param-manipulation.h (class ipa_param_body_adjustments): New
> > 	members remap_with_debug_expressions, m_dead_ssa_debug_equiv,
> > 	m_dead_stmt_debug_equiv and prepare_debug_expressions.  Added
> > 	parameter to mark_dead_statements.
> > 	* ipa-param-manipulation.c: Include tree-phinodes.h and cfgexpand.h.
> > 	(ipa_param_body_adjustments::mark_dead_statements): New parameter
> > 	debugstack, push into it all SSA names used in debug statements,
> > 	produce m_dead_ssa_debug_equiv mapping for the removed param.
> > 	(replace_with_mapped_expr): New function.
> > 	(ipa_param_body_adjustments::remap_with_debug_expressions): Likewise.
> > 	(ipa_param_body_adjustments::prepare_debug_expressions): Likewise.
> > 	(ipa_param_body_adjustments::common_initialization): Gather and
> > 	procecc SSA which will be removed but are in debug statements. Simplify.
> > 	(ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
> > 	new members.
> > 	* tree-inline.c (remap_gimple_stmt): Create a debug bind when possible
> > 	when avoiding a copy of an unnecessary statement.  Remap removed SSA
> > 	names in existing debug statements.
> > 	(tree_function_versioning): Do not create DEBUG_EXPR_DECL for removed
> > 	parameters if we have already done so.
> >
> > gcc/testsuite/ChangeLog:
> >
> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
> >
> > 	PR ipa/93385
> > 	* gcc.dg/guality/ipa-sra-1.c: New test.
> > ---
> >  gcc/ipa-param-manipulation.c             | 280 ++++++++++++++++++-----
> >  gcc/ipa-param-manipulation.h             |  12 +-
> >  gcc/testsuite/gcc.dg/guality/ipa-sra-1.c |  45 ++++
> >  gcc/tree-inline.c                        |  45 ++--
> >  4 files changed, 305 insertions(+), 77 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
> >
> > diff --git a/gcc/ipa-param-manipulation.c b/gcc/ipa-param-manipulation.c
> > index 26b02d7aa95..c84d669521c 100644
> > --- a/gcc/ipa-param-manipulation.c
> > +++ b/gcc/ipa-param-manipulation.c
> > @@ -43,6 +43,8 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "alloc-pool.h"
> >  #include "symbol-summary.h"
> >  #include "symtab-clones.h"
> > +#include "tree-phinodes.h"
> > +#include "cfgexpand.h"
> >  
> >  
> >  /* Actual prefixes of different newly synthetized parameters.  Keep in sync
> > @@ -972,10 +974,12 @@ ipa_param_body_adjustments::carry_over_param (tree t)
> >  
> >  /* 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.  */
> > +   remaining uses of a removed parameter on.  Push all removed SSA names that
> > +   are used within debug statements to DEBUGSTACK.  */
> >  
> >  void
> > -ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> > +ipa_param_body_adjustments::mark_dead_statements (tree dead_param,
> > +						  vec<tree> *debugstack)
> >  {
> >    /* Current IPA analyses which remove unused parameters never remove a
> >       non-gimple register ones which have any use except as parameters in other
> > @@ -987,6 +991,7 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> >      return;
> >  
> >    auto_vec<tree, 4> stack;
> > +  hash_set<tree> used_in_debug;
> >    m_dead_ssas.add (parm_ddef);
> >    stack.safe_push (parm_ddef);
> >    while (!stack.is_empty ())
> > @@ -1014,6 +1019,11 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> >  	    {
> >  	      m_dead_stmts.add (stmt);
> >  	      gcc_assert (gimple_debug_bind_p (stmt));
> > +	      if (!used_in_debug.contains (t))
> > +		{
> > +		  used_in_debug.add (t);
> > +		  debugstack->safe_push (t);
> > +		}
> >  	    }
> >  	  else if (gimple_code (stmt) == GIMPLE_PHI)
> >  	    {
> > @@ -1046,6 +1056,149 @@ ipa_param_body_adjustments::mark_dead_statements (tree dead_param)
> >  	    gcc_unreachable ();
> >  	}
> >      }
> > +
> > +  if (!MAY_HAVE_DEBUG_STMTS)
> > +    {
> > +      gcc_assert (debugstack->is_empty ());
> > +      return;
> > +    }
> > +
> > +  tree dp_ddecl = make_node (DEBUG_EXPR_DECL);
> > +  DECL_ARTIFICIAL (dp_ddecl) = 1;
> > +  TREE_TYPE (dp_ddecl) = TREE_TYPE (dead_param);
> > +  SET_DECL_MODE (dp_ddecl, DECL_MODE (dead_param));
> > +  m_dead_ssa_debug_equiv.put (parm_ddef, dp_ddecl);
> > +}
> > +
> > +/* Callback to walk_tree.  If REMAP is an SSA_NAME that is present in hash_map
> > +   passed in DATA, replace it with unshared version of what it was mapped
> > +   to.  */
> > +
> > +static tree
> > +replace_with_mapped_expr (tree *remap, int *walk_subtrees, void *data)
> > +{
> > +  if (TYPE_P (*remap))
> > +    {
> > +      *walk_subtrees = 0;
> > +      return 0;
> > +    }
> > +  if (TREE_CODE (*remap) != SSA_NAME)
> > +    return 0;
> > +
> > +  *walk_subtrees = 0;
> > +
> > +  hash_map<tree, tree> *equivs = (hash_map<tree, tree> *) data;
> > +  if (tree *p = equivs->get (*remap))
> > +    *remap = unshare_expr (*p);
> > +  return 0;
> > +}
> > +
> > +/* Replace all occurances of SSAs in m_dead_ssa_debug_equiv in t with what they
> > +   are mapped to.  */
> > +
> > +void
> > +ipa_param_body_adjustments::remap_with_debug_expressions (tree *t)
> > +{
> > +  /* If *t is an SSA_NAME which should have its debug statements reset, it is
> > +     mapped to NULL in the hash_map.  We need to handle that case separately or
> > +     otherwise the walker would segfault.  No expression that is more
> > +     complicated than that can have its operands mapped to NULL.  */
> > +  if (TREE_CODE (*t) == SSA_NAME)
> > +    {
> > +      if (tree *p = m_dead_ssa_debug_equiv.get (*t))
> > +	*t = *p;
> > +    }
> > +  else
> > +    walk_tree (t, replace_with_mapped_expr, &m_dead_ssa_debug_equiv, NULL);
> > +}
> > +
> > +/* For an SSA_NAME DEAD_SSA which is about to be DCEd because it is based on a
> > +   useless parameter, prepare an expression that should represent it in
> > +   debug_binds in the cloned function and add a mapping from DEAD_SSA to
> > +   m_dead_ssa_debug_equiv.  That mapping is to NULL when the associated
> > +   debug_statement has to be reset instead.  In such case return false,
> > +   ottherwise return true.  If DEAD_SSA comes from a basic block which is not
> > +   about to be copied, ignore it and return true.  */
> > +
> > +bool
> > +ipa_param_body_adjustments::prepare_debug_expressions (tree dead_ssa)
> > +{
> > +  gcc_checking_assert (m_dead_ssas.contains (dead_ssa));
> > +  if (tree *d = m_dead_ssa_debug_equiv.get (dead_ssa))
> > +    return (*d != NULL_TREE);
> > +
> > +  gcc_assert (!SSA_NAME_IS_DEFAULT_DEF (dead_ssa));
> > +  gimple *def = SSA_NAME_DEF_STMT (dead_ssa);
> > +  if (m_id->blocks_to_copy
> > +      && !bitmap_bit_p (m_id->blocks_to_copy, gimple_bb (def)->index))
> > +    return true;
> > +
> > +  if (gimple_code (def) == GIMPLE_PHI)
> > +    {
> > +      /* In theory, we could ignore all SSAs coming from BBs not in
> > +	 m_id->blocks_to_copy but at the time of the writing this code that
> > +	 should never really be the case because only fnsplit uses that bitmap,
> > +	 so don't bother.  */
> > +      tree value = degenerate_phi_result (as_a <gphi *> (def));
> > +      if (!value
> > +	  || (m_dead_ssas.contains (value)
> > +	      && !prepare_debug_expressions (value)))
> > +	{
> > +	  m_dead_ssa_debug_equiv.put (dead_ssa, NULL_TREE);
> > +	  return false;
> > +	}
> > +
> > +      gcc_assert (TREE_CODE (value) == SSA_NAME);
> > +      tree *d = m_dead_ssa_debug_equiv.get (value);
> > +      m_dead_ssa_debug_equiv.put (dead_ssa, *d);
> > +      return true;
> > +    }
> > +
> > +  bool lost = false;
> > +  use_operand_p use_p;
> > +  ssa_op_iter oi;
> > +  FOR_EACH_PHI_OR_STMT_USE (use_p, def, oi, SSA_OP_USE)
> > +    {
> > +      tree use = USE_FROM_PTR (use_p);
> > +      if (m_dead_ssas.contains (use)
> > +	  && !prepare_debug_expressions (use))
> > +	{
> > +	  lost = true;
> > +	  break;
> > +	}
> > +    }
> > +
> > +  if (lost)
> > +    {
> > +      m_dead_ssa_debug_equiv.put (dead_ssa, NULL_TREE);
> > +      return false;
> > +    }
> > +
> > +  if (is_gimple_assign (def))
> > +    {
> > +      gcc_assert (!gimple_clobber_p (def));
> > +      if (gimple_assign_copy_p (def)
> > +	  && TREE_CODE (gimple_assign_rhs1 (def)) == SSA_NAME)
> > +	{
> > +	  tree *d = m_dead_ssa_debug_equiv.get (gimple_assign_rhs1 (def));
> > +	  m_dead_ssa_debug_equiv.put (dead_ssa, *d);
> > +	  return (*d != NULL_TREE);
> > +	}
> > +
> > +      tree val = gimple_assign_rhs_to_tree (def);
> > +      SET_EXPR_LOCATION (val, UNKNOWN_LOCATION);
> > +      remap_with_debug_expressions (&val);
> > +
> > +      tree vexpr = make_node (DEBUG_EXPR_DECL);
> > +      DECL_ARTIFICIAL (vexpr) = 1;
> > +      TREE_TYPE (vexpr) = TREE_TYPE (val);
> > +      SET_DECL_MODE (vexpr, TYPE_MODE (TREE_TYPE (val)));
> > +      m_dead_stmt_debug_equiv.put (def, val);
> > +      m_dead_ssa_debug_equiv.put (dead_ssa, vexpr);
> > +      return true;
> > +    }
> > +  else
> > +    gcc_unreachable ();
> >  }
> >  
> >  /* Common initialization performed by all ipa_param_body_adjustments
> > @@ -1137,65 +1290,21 @@ ipa_param_body_adjustments::common_initialization (tree old_fndecl,
> >  	gcc_unreachable ();
> >      }
> >  
> > -
> > -  /* As part of body modifications, we will also have to replace remaining uses
> > -     of remaining uses of removed PARM_DECLs (which do not however use the
> > -     initial value) with their VAR_DECL copies.
> > -
> > -     We do this differently with and without m_id.  With m_id, we rely on its
> > -     mapping and create a replacement straight away.  Without it, we have our
> > -     own mechanism for which we have to populate m_removed_decls vector.  Just
> > -     don't mix them, that is why you should not call
> > -     replace_removed_params_ssa_names or perform_cfun_body_modifications when
> > -     you construct with ID not equal to NULL.  */
> > -
> > -  unsigned op_len = m_oparms.length ();
> > -  for (unsigned i = 0; i < op_len; i++)
> > -    if (!kept[i])
> > -      {
> > -	if (m_id)
> > -	  {
> > -	    if (!m_id->decl_map->get (m_oparms[i]))
> > -	      {
> > -		tree var = copy_decl_to_var (m_oparms[i], m_id);
> > -		insert_decl_map (m_id, m_oparms[i], var);
> > -		/* 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
> > -	  {
> > -	    m_removed_decls.safe_push (m_oparms[i]);
> > -	    m_removed_map.put (m_oparms[i], m_removed_decls.length () - 1);
> > -	  }
> > -      }
> > -
> > -  if (!MAY_HAVE_DEBUG_STMTS)
> > -    return;
> > -
> > -  /* Finally, when generating debug info, we fill vector m_reset_debug_decls
> > -    with removed parameters declarations.  We do this in order to re-map their
> > -    debug bind statements and create debug decls for them.  */
> > -
> >    if (tree_map)
> >      {
> > -      /* Do not output debuginfo for parameter declarations as if they vanished
> > -	 when they were in fact replaced by a constant.  */
> > +      /* Do not treat parameters which were replaced with a constant as
> > +	 completely vanished.  */
> >        auto_vec <int, 16> index_mapping;
> >        bool need_remap = false;
> > -      clone_info *info = clone_info::get (m_id->src_node);
> >  
> > -      if (m_id && info && info->param_adjustments)
> > +      if (m_id)
> >  	{
> > -	  ipa_param_adjustments *prev_adjustments = info->param_adjustments;
> > -	  prev_adjustments->get_updated_indices (&index_mapping);
> > -	  need_remap = true;
> > +	  clone_info *cinfo = clone_info::get (m_id->src_node);
> > +	  if (cinfo && cinfo->param_adjustments)
> > +	    {
> > +	      cinfo->param_adjustments->get_updated_indices (&index_mapping);
> > +	      need_remap = true;
> > +	    }
> >  	}
> >  
> >        for (unsigned i = 0; i < tree_map->length (); i++)
> > @@ -1208,9 +1317,52 @@ ipa_param_body_adjustments::common_initialization (tree old_fndecl,
> >  	}
> >      }
> >  
> > +  /* As part of body modifications, we will also have to replace remaining uses
> > +     of remaining uses of removed PARM_DECLs (which do not however use the
> > +     initial value) with their VAR_DECL copies.
> > +
> > +     We do this differently with and without m_id.  With m_id, we rely on its
> > +     mapping and create a replacement straight away.  Without it, we have our
> > +     own mechanism for which we have to populate m_removed_decls vector.  Just
> > +     don't mix them, that is why you should not call
> > +     replace_removed_params_ssa_names or perform_cfun_body_modifications when
> > +     you construct with ID not equal to NULL.  */
> > +
> > +  auto_vec<tree, 8> ssas_to_process_debug;
> > +  unsigned op_len = m_oparms.length ();
> >    for (unsigned i = 0; i < op_len; i++)
> > -    if (!kept[i] && is_gimple_reg (m_oparms[i]))
> > -      m_reset_debug_decls.safe_push (m_oparms[i]);
> > +    if (!kept[i])
> > +      {
> > +	if (m_id)
> > +	  {
> > +	    gcc_assert (!m_id->decl_map->get (m_oparms[i]));
> > +	    tree var = copy_decl_to_var (m_oparms[i], m_id);
> > +	    insert_decl_map (m_id, m_oparms[i], var);
> > +	    /* 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], &ssas_to_process_debug);
> > +	    if (MAY_HAVE_DEBUG_STMTS
> > +		&& is_gimple_reg (m_oparms[i]))
> > +	      m_reset_debug_decls.safe_push (m_oparms[i]);
> > +	  }
> > +	else
> > +	  {
> > +	    m_removed_decls.safe_push (m_oparms[i]);
> > +	    m_removed_map.put (m_oparms[i], m_removed_decls.length () - 1);
> > +	    if (MAY_HAVE_DEBUG_STMTS
> > +		&& !kept[i]
> > +		&& is_gimple_reg (m_oparms[i]))
> > +	      m_reset_debug_decls.safe_push (m_oparms[i]);
> > +	  }
> > +      }
> > +
> > +  while (!ssas_to_process_debug.is_empty ())
> > +    prepare_debug_expressions (ssas_to_process_debug.pop ());
> >  }
> >  
> >  /* Constructor of ipa_param_body_adjustments from a simple list of
> > @@ -1224,9 +1376,9 @@ ipa_param_body_adjustments
> >  			      tree fndecl)
> >    : m_adj_params (adj_params), m_adjustments (NULL), 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)
> > +    m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (), 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);
> >  }
> > @@ -1241,7 +1393,8 @@ ipa_param_body_adjustments
> >  			      tree fndecl)
> >    : m_adj_params (adjustments->m_adj_params), m_adjustments (adjustments),
> >      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_dead_ssas (), m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (),
> > +    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)
> >  {
> > @@ -1264,8 +1417,9 @@ ipa_param_body_adjustments
> >  			      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_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_dead_ssas (), m_dead_ssa_debug_equiv (), m_dead_stmt_debug_equiv (),
> > +    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);
> > diff --git a/gcc/ipa-param-manipulation.h b/gcc/ipa-param-manipulation.h
> > index afcbc09bf33..9440cbfc56c 100644
> > --- a/gcc/ipa-param-manipulation.h
> > +++ b/gcc/ipa-param-manipulation.h
> > @@ -328,6 +328,9 @@ public:
> >  			   gimple *orig_stmt);
> >    /* Return the new chain of parameters.  */
> >    tree get_new_param_chain ();
> > +  /* Replace all occurances of SSAs in m_dead_ssa_debug_equiv in t with what
> > +     they are mapped to.  */
> > +  void remap_with_debug_expressions (tree *t);
> >  
> >    /* Pointers to data structures defining how the function should be
> >       modified.  */
> > @@ -348,6 +351,12 @@ public:
> >    hash_set<gimple *> m_dead_stmts;
> >    hash_set<tree> m_dead_ssas;
> >  
> > +  /* Mapping from DCEd SSAs to what their potential debug_binds should be.  */
> > +  hash_map<tree, tree> m_dead_ssa_debug_equiv;
> > +  /* Mapping from DCEd statements to debug expressions that will be placed on
> > +     the RHS of debug statement that will replace this one.  */
> > +  hash_map<gimple *, tree> m_dead_stmt_debug_equiv;
> > +
> >  private:
> >    void common_initialization (tree old_fndecl, tree *vars,
> >  			      vec<ipa_replace_map *, va_gc> *tree_map);
> > @@ -361,7 +370,8 @@ private:
> >    bool modify_call_stmt (gcall **stmt_p, gimple *orig_stmt);
> >    bool modify_cfun_body ();
> >    void reset_debug_stmts ();
> > -  void mark_dead_statements (tree dead_param);
> > +  void mark_dead_statements (tree dead_param, vec<tree> *debugstack);
> > +  bool prepare_debug_expressions (tree dead_ssa);
> >  
> >    /* Declaration of the function that is being transformed.  */
> >  
> > diff --git a/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c b/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
> > new file mode 100644
> > index 00000000000..5434b3d7665
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/guality/ipa-sra-1.c
> > @@ -0,0 +1,45 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-g -fno-ipa-icf" } */
> > +
> > +
> > +void __attribute__((noipa))
> > +use (int x)
> > +{
> > +  asm volatile ("" : : "r" (x) : "memory");
> > +}
> > +
> > +static int __attribute__((noinline))
> > +bar (int i, int k)
> > +{
> > +  asm ("" : "+r" (i));
> > +  use (i);		/* { dg-final { gdb-test . "k" "3" { xfail *-*-* } } } */
> > +  return 6;
> > +}
> > +
> > +volatile int v;
> > +
> > +static int __attribute__((noinline))
> > +foo (int i, int k)
> > +{
> > +  int r;
> > +  v = 9;
> > +  k = (k + 14)/k;
> > +  r = bar (i, k);		/* { dg-final { gdb-test . "k" "3" } } */
> > +  return r;
> > +}
> > +
> > +volatile int v;
> > +
> > +int __attribute__((noipa))
> > +get_val1 (void)  {return 20;}
> > +int __attribute__((noipa))
> > +get_val2 (void)  {return 7;}
> > +
> > +int
> > +main (void)
> > +{
> > +  int k = get_val2 ();
> > +  int r = foo (get_val1 (), k);
> > +  v = r + k;   /* k has to live accross the call or all is probably lost  */
> > +  return 0;
> > +}
> > diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
> > index e292a144967..6cf4a0e9f36 100644
> > --- a/gcc/tree-inline.c
> > +++ b/gcc/tree-inline.c
> > @@ -1529,7 +1529,21 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
> >    if (!is_gimple_debug (stmt)
> >        && id->param_body_adjs
> >        && id->param_body_adjs->m_dead_stmts.contains (stmt))
> > -    return NULL;
> > +    {
> > +      tree *dval = id->param_body_adjs->m_dead_stmt_debug_equiv.get (stmt);
> > +      if (!dval)
> > +	return NULL;
> > +
> > +      gcc_assert (is_gimple_assign (stmt));
> > +      tree lhs = gimple_assign_lhs (stmt);
> > +      tree *dvar = id->param_body_adjs->m_dead_ssa_debug_equiv.get (lhs);
> > +      gdebug *bind = gimple_build_debug_bind (*dvar, *dval, stmt);
> > +      if (id->reset_location)
> > +	gimple_set_location (bind, input_location);
> > +      id->debug_stmts.safe_push (bind);
> > +      gimple_seq_add_stmt (&stmts, bind);
> > +      return stmts;
> > +    }
> >  
> >    /* Begin by recognizing trees that we'll completely rewrite for the
> >       inlining context.  Our output for these trees is completely
> > @@ -1807,15 +1821,13 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
> >  
> >        if (gimple_debug_bind_p (stmt))
> >  	{
> > -	  tree value;
> > +	  tree var = gimple_debug_bind_get_var (stmt);
> > +	  tree value = gimple_debug_bind_get_value (stmt);
> >  	  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),
> > -				       value, stmt);
> > +	    id->param_body_adjs->remap_with_debug_expressions (&value);
> > +
> > +	  gdebug *copy = gimple_build_debug_bind (var, value, stmt);
> >  	  if (id->reset_location)
> >  	    gimple_set_location (copy, input_location);
> >  	  id->debug_stmts.safe_push (copy);
> > @@ -6446,7 +6458,6 @@ tree_function_versioning (tree old_decl, tree new_decl,
> >  	     in the debug info that var (whole DECL_ORIGIN is the parm
> >  	     PARM_DECL) is optimized away, but could be looked up at the
> >  	     call site as value of D#X there.  */
> > -	  tree vexpr;
> >  	  gimple_stmt_iterator cgsi
> >  	    = gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
> >  	  gimple *def_temp;
> > @@ -6454,17 +6465,25 @@ tree_function_versioning (tree old_decl, tree new_decl,
> >  	  i = vec_safe_length (*debug_args);
> >  	  do
> >  	    {
> > +	      tree vexpr = NULL_TREE;
> >  	      i -= 2;
> >  	      while (var != NULL_TREE
> >  		     && DECL_ABSTRACT_ORIGIN (var) != (**debug_args)[i])
> >  		var = TREE_CHAIN (var);
> >  	      if (var == NULL_TREE)
> >  		break;
> > -	      vexpr = make_node (DEBUG_EXPR_DECL);
> >  	      tree parm = (**debug_args)[i];
> > -	      DECL_ARTIFICIAL (vexpr) = 1;
> > -	      TREE_TYPE (vexpr) = TREE_TYPE (parm);
> > -	      SET_DECL_MODE (vexpr, DECL_MODE (parm));
> > +	      if (tree parm_ddef = ssa_default_def (id.src_cfun, parm))
> > +		if (tree *d
> > +		    = param_body_adjs->m_dead_ssa_debug_equiv.get (parm_ddef))
> > +		  vexpr = *d;
> > +	      if (!vexpr)
> > +		{
> > +		  vexpr = make_node (DEBUG_EXPR_DECL);
> > +		  DECL_ARTIFICIAL (vexpr) = 1;
> > +		  TREE_TYPE (vexpr) = TREE_TYPE (parm);
> > +		  SET_DECL_MODE (vexpr, DECL_MODE (parm));
> > +		}
> >  	      def_temp = gimple_build_debug_bind (var, vexpr, NULL);
> >  	      gsi_insert_before (&cgsi, def_temp, GSI_NEW_STMT);
> >  	      def_temp = gimple_build_debug_source_bind (vexpr, parm, NULL);
> > -- 
> > 2.33.0
>
  

Hi,

On Wed, Nov 03 2021, Richard Biener wrote:
> On Mon, 1 Nov 2021, Martin Jambor wrote:
>
>> Hello,
>> 
>> I'd like to ping this patch.
>> 
>> Thanks,
>> 
>> Martin
>> 
>> 
>> On Wed, Oct 13 2021, Martin Jambor wrote:
>> > Hi,
>> >
>> > in spring I added code eliminating any statements using parameters
>> > removed by IPA passes (to fix PR 93385).  That patch fixed issues such
>> > as divisions by zero that such code could perform but it only reset
>> > all affected debug bind statements, this one updates them with
>> > expressions which can allow the debugger to print the removed value -
>> > see the added test-case for an example.
>> >
[...]
>> >
>> > Bootstrapped and tested on x86_64-linux, i686-linux and (long time
>> > ago) on aarch64-linux.  Also LTO-bootstrapped and on x86_64-linux.
>> >
>> > Perhaps it is good to go to trunk?
>
> I think the patch is OK for trunk.  It would be nice to common the

Thank you very much, I will commit the patch shortly after a rebase and
a final test.

>
> +      tree vexpr = make_node (DEBUG_EXPR_DECL);
> +      DECL_ARTIFICIAL (vexpr) = 1;
> +      TREE_TYPE (vexpr) = TREE_TYPE (val);
> +      SET_DECL_MODE (vexpr, TYPE_MODE (TREE_TYPE (val)));
>
> blob that exists all over the GCC code base with a new
> build_debug_expr_decl (tree type) (next to tree.c:build_decl).
>

That makes sense, I'll prepare a patch as a follow-up.

A minority of places in GCC which produce a DEBUG_DECL_EXPR however set
its mode like cfgexpand.c does:

    tree vexpr = make_node (DEBUG_EXPR_DECL);
    DECL_ARTIFICIAL (vexpr) = 1;
    TREE_TYPE (vexpr) = TREE_TYPE (value);
    if (DECL_P (value))
      mode = DECL_MODE (value);
    else
      mode = TYPE_MODE (TREE_TYPE (value));
    SET_DECL_MODE (vexpr, mode);

Should build_debug_expr_decl's parameter be perhaps more general,
allowing both DECLs, TYPEs and use its TREE_TYPE if it is neither)?

Or should I leave such places as they are and only convert those that
set the mode to TYPE_MODE (type)?

Thanks,

Martin


>> >
>> > gcc/ChangeLog:
>> >
>> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
>> >
>> > 	PR ipa/93385
>> > 	* ipa-param-manipulation.h (class ipa_param_body_adjustments): New
>> > 	members remap_with_debug_expressions, m_dead_ssa_debug_equiv,
>> > 	m_dead_stmt_debug_equiv and prepare_debug_expressions.  Added
>> > 	parameter to mark_dead_statements.
>> > 	* ipa-param-manipulation.c: Include tree-phinodes.h and cfgexpand.h.
>> > 	(ipa_param_body_adjustments::mark_dead_statements): New parameter
>> > 	debugstack, push into it all SSA names used in debug statements,
>> > 	produce m_dead_ssa_debug_equiv mapping for the removed param.
>> > 	(replace_with_mapped_expr): New function.
>> > 	(ipa_param_body_adjustments::remap_with_debug_expressions): Likewise.
>> > 	(ipa_param_body_adjustments::prepare_debug_expressions): Likewise.
>> > 	(ipa_param_body_adjustments::common_initialization): Gather and
>> > 	procecc SSA which will be removed but are in debug statements. Simplify.
>> > 	(ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
>> > 	new members.
>> > 	* tree-inline.c (remap_gimple_stmt): Create a debug bind when possible
>> > 	when avoiding a copy of an unnecessary statement.  Remap removed SSA
>> > 	names in existing debug statements.
>> > 	(tree_function_versioning): Do not create DEBUG_EXPR_DECL for removed
>> > 	parameters if we have already done so.
>> >
>> > gcc/testsuite/ChangeLog:
>> >
>> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
>> >
>> > 	PR ipa/93385
>> > 	* gcc.dg/guality/ipa-sra-1.c: New test.
  

On Thu, 4 Nov 2021, Martin Jambor wrote:

> Hi,
> 
> On Wed, Nov 03 2021, Richard Biener wrote:
> > On Mon, 1 Nov 2021, Martin Jambor wrote:
> >
> >> Hello,
> >> 
> >> I'd like to ping this patch.
> >> 
> >> Thanks,
> >> 
> >> Martin
> >> 
> >> 
> >> On Wed, Oct 13 2021, Martin Jambor wrote:
> >> > Hi,
> >> >
> >> > in spring I added code eliminating any statements using parameters
> >> > removed by IPA passes (to fix PR 93385).  That patch fixed issues such
> >> > as divisions by zero that such code could perform but it only reset
> >> > all affected debug bind statements, this one updates them with
> >> > expressions which can allow the debugger to print the removed value -
> >> > see the added test-case for an example.
> >> >
> [...]
> >> >
> >> > Bootstrapped and tested on x86_64-linux, i686-linux and (long time
> >> > ago) on aarch64-linux.  Also LTO-bootstrapped and on x86_64-linux.
> >> >
> >> > Perhaps it is good to go to trunk?
> >
> > I think the patch is OK for trunk.  It would be nice to common the
> 
> Thank you very much, I will commit the patch shortly after a rebase and
> a final test.
> 
> >
> > +      tree vexpr = make_node (DEBUG_EXPR_DECL);
> > +      DECL_ARTIFICIAL (vexpr) = 1;
> > +      TREE_TYPE (vexpr) = TREE_TYPE (val);
> > +      SET_DECL_MODE (vexpr, TYPE_MODE (TREE_TYPE (val)));
> >
> > blob that exists all over the GCC code base with a new
> > build_debug_expr_decl (tree type) (next to tree.c:build_decl).
> >
> 
> That makes sense, I'll prepare a patch as a follow-up.
> 
> A minority of places in GCC which produce a DEBUG_DECL_EXPR however set
> its mode like cfgexpand.c does:
> 
>     tree vexpr = make_node (DEBUG_EXPR_DECL);
>     DECL_ARTIFICIAL (vexpr) = 1;
>     TREE_TYPE (vexpr) = TREE_TYPE (value);
>     if (DECL_P (value))
>       mode = DECL_MODE (value);
>     else
>       mode = TYPE_MODE (TREE_TYPE (value));
>     SET_DECL_MODE (vexpr, mode);

I'm not sure why the difference matters - I'd have to dig in history.
The only place where this tends to differ is for FIELD_DECLs, but
'value' shouldn't be such one.  And looking at the "value" for this
looks odd anyhow.  That said, I'd simply leave those cases
in place (or simply re-set the mode as they do now).

> Should build_debug_expr_decl's parameter be perhaps more general,
> allowing both DECLs, TYPEs and use its TREE_TYPE if it is neither)?

No, I don't like that option much.

> Or should I leave such places as they are and only convert those that
> set the mode to TYPE_MODE (type)?
> 
> Thanks,
> 
> Martin
> 
> 
> >> >
> >> > gcc/ChangeLog:
> >> >
> >> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
> >> >
> >> > 	PR ipa/93385
> >> > 	* ipa-param-manipulation.h (class ipa_param_body_adjustments): New
> >> > 	members remap_with_debug_expressions, m_dead_ssa_debug_equiv,
> >> > 	m_dead_stmt_debug_equiv and prepare_debug_expressions.  Added
> >> > 	parameter to mark_dead_statements.
> >> > 	* ipa-param-manipulation.c: Include tree-phinodes.h and cfgexpand.h.
> >> > 	(ipa_param_body_adjustments::mark_dead_statements): New parameter
> >> > 	debugstack, push into it all SSA names used in debug statements,
> >> > 	produce m_dead_ssa_debug_equiv mapping for the removed param.
> >> > 	(replace_with_mapped_expr): New function.
> >> > 	(ipa_param_body_adjustments::remap_with_debug_expressions): Likewise.
> >> > 	(ipa_param_body_adjustments::prepare_debug_expressions): Likewise.
> >> > 	(ipa_param_body_adjustments::common_initialization): Gather and
> >> > 	procecc SSA which will be removed but are in debug statements. Simplify.
> >> > 	(ipa_param_body_adjustments::ipa_param_body_adjustments): Initialize
> >> > 	new members.
> >> > 	* tree-inline.c (remap_gimple_stmt): Create a debug bind when possible
> >> > 	when avoiding a copy of an unnecessary statement.  Remap removed SSA
> >> > 	names in existing debug statements.
> >> > 	(tree_function_versioning): Do not create DEBUG_EXPR_DECL for removed
> >> > 	parameters if we have already done so.
> >> >
> >> > gcc/testsuite/ChangeLog:
> >> >
> >> > 2021-03-29  Martin Jambor  <mjambor@suse.cz>
> >> >
> >> > 	PR ipa/93385
> >> > 	* gcc.dg/guality/ipa-sra-1.c: New test.
>