OpenMP: GC unused SIMD clones

SIMD clones are created during the IPA phase when it is not known whether
or not the vectorizer can use them.  Clones for functions with external
linkage are part of the ABI, but local clones can be GC'ed if no calls are
found in the compilation unit after vectorization.

gcc/ChangeLog
	* cgraph.h (struct cgraph_node): Add gc_candidate bit, modify
	default constructor to initialize it.
	* cgraphunit.cc (expand_all_functions): Save gc_candidate functions
	for last and iterate to handle recursive calls.  Delete leftover
	candidates at the end.
	* omp-simd-clone.cc (simd_clone_create): Set gc_candidate bit
	on local clones.
	* tree-vect-stmts.cc (vectorizable_simd_clone_call): Clear
	gc_candidate bit when a clone is used.

gcc/testsuite/ChangeLog
	* g++.dg/gomp/target-simd-clone-1.C: Tweak to test
	that the unused clone is GC'ed.
	* gcc.dg/gomp/target-simd-clone-1.c: Likewise.

(cherry picked from commit 0425ae780fb2b055d985b5719af5edfaaad5e980)

diff --git a/gcc/ChangeLog.omp b/gcc/ChangeLog.omp
index b54037bee272d1920d897a4a21eb752116ac32e7..917bb606a0f98f2e6e81095321e58c73d63b7da8 100644 (file)
--- a/gcc/ChangeLog.omp
+++ b/gcc/ChangeLog.omp
@@ -1,3 +1,18 @@
+2023-01-03  Sandra Loosemore  <sandra@codesourcery.com>
+
+       Backported from master:
+       2023-01-03  Sandra Loosemore  <sandra@codesourcery.com>
+
+       * cgraph.h (struct cgraph_node): Add gc_candidate bit, modify
+       default constructor to initialize it.
+       * cgraphunit.cc (expand_all_functions): Save gc_candidate functions
+       for last and iterate to handle recursive calls.  Delete leftover
+       candidates at the end.
+       * omp-simd-clone.cc (simd_clone_create): Set gc_candidate bit
+       on local clones.
+       * tree-vect-stmts.cc (vectorizable_simd_clone_call): Clear
+       gc_candidate bit when a clone is used.
+
 2022-12-21  Tobias Burnus  <tobias@codesourcery.com>
 
        Backported from master:

diff --git a/gcc/cgraph.h b/gcc/cgraph.h
index 8c512b648ee586bf319da23d271d7749673479d2..c49aaf2f0885c144b7509fcae25a83f1c628072a 100644 (file)
--- a/gcc/cgraph.h
+++ b/gcc/cgraph.h
@@ -891,7 +891,8 @@ struct GTY((tag ("SYMTAB_FUNCTION"))) cgraph_node : public symtab_node
       versionable (false), can_change_signature (false),
       redefined_extern_inline (false), tm_may_enter_irr (false),
       ipcp_clone (false), declare_variant_alt (false),
-      calls_declare_variant_alt (false), m_uid (uid), m_summary_id (-1)
+      calls_declare_variant_alt (false), gc_candidate (false),
+      m_uid (uid), m_summary_id (-1)
   {}
 
   /* Remove the node from cgraph and all inline clones inlined into it.
@@ -1490,6 +1491,10 @@ struct GTY((tag ("SYMTAB_FUNCTION"))) cgraph_node : public symtab_node
   unsigned declare_variant_alt : 1;
   /* True if the function calls declare_variant_alt functions.  */
   unsigned calls_declare_variant_alt : 1;
+  /* True if the function should only be emitted if it is used.  This flag
+     is set for local SIMD clones when they are created and cleared if the
+     vectorizer uses them.  */
+  unsigned gc_candidate : 1;
 
 private:
   /* Unique id of the node.  */

diff --git a/gcc/cgraphunit.cc b/gcc/cgraphunit.cc
index 76d541755b80d6d28ba29289508a3458110d5cc7..b949f61b76135182e76ef3e46290df012e70d36a 100644 (file)
--- a/gcc/cgraphunit.cc
+++ b/gcc/cgraphunit.cc
@@ -1987,19 +1987,52 @@ expand_all_functions (void)
 
   /* Output functions in RPO so callees get optimized before callers.  This
      makes ipa-ra and other propagators to work.
-     FIXME: This is far from optimal code layout.  */
-  for (i = new_order_pos - 1; i >= 0; i--)
-    {
-      node = order[i];
+     FIXME: This is far from optimal code layout.
+     Make multiple passes over the list to defer processing of gc
+     candidates until all potential uses are seen.  */
+  int gc_candidates = 0;
+  int prev_gc_candidates = 0;
 
-      if (node->process)
+  while (1)
+    {
+      for (i = new_order_pos - 1; i >= 0; i--)
        {
-         expanded_func_count++;
-         node->process = 0;
-         node->expand ();
+         node = order[i];
+
+         if (node->gc_candidate)
+           gc_candidates++;
+         else if (node->process)
+           {
+             expanded_func_count++;
+             node->process = 0;
+             node->expand ();
+           }
        }
+      if (!gc_candidates || gc_candidates == prev_gc_candidates)
+       break;
+      prev_gc_candidates = gc_candidates;
+      gc_candidates = 0;
     }
 
+  /* Free any unused gc_candidate functions.  */
+  if (gc_candidates)
+    for (i = new_order_pos - 1; i >= 0; i--)
+      {
+       node = order[i];
+       if (node->gc_candidate)
+         {
+           struct function *fn = DECL_STRUCT_FUNCTION (node->decl);
+           if (symtab->dump_file)
+             fprintf (symtab->dump_file,
+                      "Deleting unused function %s\n",
+                      IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)));
+           node->process = false;
+           free_dominance_info (fn, CDI_DOMINATORS);
+           free_dominance_info (fn, CDI_POST_DOMINATORS);
+           node->release_body (false);
+         }
+      }
+
   if (dump_file)
     fprintf (dump_file, "Expanded functions with time profile (%s):%u/%u\n",
             main_input_filename, profiled_func_count, expanded_func_count);

diff --git a/gcc/omp-simd-clone.cc b/gcc/omp-simd-clone.cc
index 526193dc59ef991ae5bcc580d586fea67f972255..3c35700cfe629a400671d3b11d9c10684e9a9b69 100644 (file)
--- a/gcc/omp-simd-clone.cc
+++ b/gcc/omp-simd-clone.cc
@@ -702,6 +702,11 @@ simd_clone_create (struct cgraph_node *old_node, bool force_local)
        = old_node->calls_declare_variant_alt;
     }
 
+  /* Mark clones with internal linkage as gc'able, so they will not be
+     emitted unless the vectorizer can actually use them.  */
+  if (!TREE_PUBLIC (new_node->decl))
+    new_node->gc_candidate = true;
+
   return new_node;
 }
 

diff --git a/gcc/testsuite/ChangeLog.omp b/gcc/testsuite/ChangeLog.omp
index 7475f6d597f8daa4f2c7b331d14910c6dddb8d52..d018d9b0dbc80adee0b4c6030fe6f21ac78695b3 100644 (file)
--- a/gcc/testsuite/ChangeLog.omp
+++ b/gcc/testsuite/ChangeLog.omp
@@ -1,3 +1,12 @@
+2023-01-03  Sandra Loosemore  <sandra@codesourcery.com>
+
+       Backported from master:
+       2023-01-03  Sandra Loosemore  <sandra@codesourcery.com>
+
+       * g++.dg/gomp/target-simd-clone-1.C: Tweak to test
+       that the unused clone is GC'ed.
+       * gcc.dg/gomp/target-simd-clone-1.c: Likewise.
+
 2022-12-21  Tobias Burnus  <tobias@codesourcery.com>
 
        Backport from mainline:

diff --git a/gcc/testsuite/g++.dg/gomp/target-simd-clone-1.C b/gcc/testsuite/g++.dg/gomp/target-simd-clone-1.C
index 10b5ac38812a05bb60a14f319f2e435754c61ec6..b96473642bbe53392dd5a08f6823bf6b939b794d 100644 (file)
--- a/gcc/testsuite/g++.dg/gomp/target-simd-clone-1.C
+++ b/gcc/testsuite/g++.dg/gomp/target-simd-clone-1.C
@@ -1,5 +1,5 @@
 /* { dg-options "-fopenmp -O2" } */
-/* { dg-additional-options "-fopenmp-target-simd-clone=any -fdump-ipa-simdclone-details" } */
+/* { dg-additional-options "-fopenmp-target-simd-clone=any -fdump-ipa-simdclone-details -fdump-ipa-cgraph" } */
 
 /* Test that simd clones are generated for functions with "declare target".  */
 
@@ -23,3 +23,8 @@ void callit (int *a, int *b, int *c)
 
 /* { dg-final { scan-ipa-dump "Generated local clone _ZGV.*N.*__Z5additii" "simdclone" { target x86_64-*-* } } } */
 /* { dg-final { scan-ipa-dump "Generated local clone _ZGV.*M.*__Z5additii" "simdclone" { target x86_64-*-* } } } */
+
+/* Only the "N" clone is used.  The other one should be GC'ed.  */
+
+/* { dg-final { scan-ipa-dump "Deleting unused function _ZGV.*M.*__Z5additii" "cgraph" { target x86_64-*-* } } } */
+

diff --git a/gcc/testsuite/gcc.dg/gomp/target-simd-clone-1.c b/gcc/testsuite/gcc.dg/gomp/target-simd-clone-1.c
index 388dc2a956cafdb7b36734b9a3f5619c4866e7c2..0d74aa971f93dff49499a54e6f1fbe966f4f10de 100644 (file)
--- a/gcc/testsuite/gcc.dg/gomp/target-simd-clone-1.c
+++ b/gcc/testsuite/gcc.dg/gomp/target-simd-clone-1.c
@@ -1,5 +1,5 @@
 /* { dg-options "-fopenmp -O2" } */
-/* { dg-additional-options "-fopenmp-target-simd-clone=any -fdump-ipa-simdclone-details" } */
+/* { dg-additional-options "-fopenmp-target-simd-clone=any -fdump-ipa-simdclone-details -fdump-ipa-cgraph" } */
 
 /* Test that simd clones are generated for functions with "declare target".  */
 
@@ -23,3 +23,7 @@ void callit (int *a, int *b, int *c)
 
 /* { dg-final { scan-ipa-dump "Generated local clone _ZGV.*N.*_addit" "simdclone" { target x86_64-*-* } } } */
 /* { dg-final { scan-ipa-dump "Generated local clone _ZGV.*M.*_addit" "simdclone" { target x86_64-*-* } } } */
+
+/* Only the "N" clone is used.  The other one should be GC'ed.  */
+
+/* { dg-final { scan-ipa-dump "Deleting unused function _ZGV.*M.*_addit" "cgraph" { target x86_64-*-* } } } */

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index ab45c1ff3f979b6f534f774a51eb2e6bdcd40815..31e96d04d63797bdb427e9e88205e46fecf39eb5 100644 (file)
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -4613,6 +4613,9 @@ vectorizable_simd_clone_call (vec_info *vinfo, stmt_vec_info stmt_info,
     }
   vargs.release ();
 
+  /* Mark the clone as no longer being a candidate for GC.  */
+  bestn->gc_candidate = false;
+
   /* The call in STMT might prevent it from being removed in dce.
      We however cannot remove it here, due to the way the ssa name
      it defines is mapped to the new definition.  So just replace