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tree-optimization/116463 - complex lowering leaves around dead stmts

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Complex lowering generally replaces existing complex defs with
COMPLEX_EXPRs but those might be dead when it can always refer to
components from the lattice.  This in turn can pessimize followup
transforms like forwprop and reassoc, the following makes sure to
get rid of dead COMPLEX_EXPRs generated by using
simple_dce_from_worklist.

	PR tree-optimization/116463
	* tree-complex.cc: Include tree-ssa-dce.h.
	(dce_worklist): New global.
	(update_complex_assignment): Add SSA def to the DCE worklist.
	(tree_lower_complex): Perform DCE.
This commit is contained in:
Richard Biener 2024-08-23 13:44:29 +02:00 • committed by Richard Biener
parent a35dd276cb
commit de1923f9f4
1 changed files with 9 additions and 0 deletions
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9
gcc/tree-complex.cc
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@ -46,6 +46,7 @@ along with GCC; see the file COPYING3. If not see
#include "case-cfn-macros.h"
#include "builtins.h"
#include "optabs-tree.h"
#include "tree-ssa-dce.h"
/* For each complex ssa name, a lattice value. We're interested in finding
out whether a complex number is degenerate in some way, having only real
@ -88,6 +89,9 @@ static vec<gphi *> phis_to_revisit;
/* BBs that need EH cleanup. */
static bitmap need_eh_cleanup;
/* SSA defs we should try to DCE. */
static bitmap dce_worklist;
/* Lookup UID in the complex_variable_components hashtable and return the
associated tree. */
static tree
@ -731,6 +735,7 @@ update_complex_assignment (gimple_stmt_iterator *gsi, tree r, tree i)
update_stmt (stmt);
if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt))
bitmap_set_bit (need_eh_cleanup, gimple_bb (stmt)->index);
bitmap_set_bit (dce_worklist, SSA_NAME_VERSION (gimple_assign_lhs (stmt)));
update_complex_components (gsi, gsi_stmt (*gsi), r, i);
}
@ -1962,6 +1967,7 @@ tree_lower_complex (void)
complex_propagate.ssa_propagate ();
need_eh_cleanup = BITMAP_ALLOC (NULL);
dce_worklist = BITMAP_ALLOC (NULL);
complex_variable_components = new int_tree_htab_type (10);
@ -2008,6 +2014,9 @@ tree_lower_complex (void)
gsi_commit_edge_inserts ();
simple_dce_from_worklist (dce_worklist, need_eh_cleanup);
BITMAP_FREE (dce_worklist);
unsigned todo
= gimple_purge_all_dead_eh_edges (need_eh_cleanup) ? TODO_cleanup_cfg : 0;
BITMAP_FREE (need_eh_cleanup);