dce: add remove_unused_locals conditionally to the todos [PR117096]

This is the updated patch with the suggestion from:
https://gcc.gnu.org/pipermail/gcc-patches/2024-October/665217.html
Where we use a second arg/param to set which passes we want to have
the remove_unused_locals on the dce.

Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	PR tree-optimization/117096
	* passes.def: Update some of the dce/cd-cde passes setting
	the 2nd arg to true.
	Also remove comment about stdarg since dce does it.
	* tree-ssa-dce.cc (pass_dce): Add remove_unused_locals_p field.
	Update set_pass_param to allow for 2nd param.
	Use remove_unused_locals_p in execute to return TODO_remove_unused_locals.
	(pass_cd_dce): Likewise.
	* tree-stdarg.cc (pass_data_stdarg): Remove TODO_remove_unused_locals.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

3 files changed, 19 insertions, 12 deletions

diff --git a/gcc/passes.def b/gcc/passes.def
index 40162ac..7d01227 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -92,7 +92,7 @@ along with GCC; see the file COPYING3.  If not see
 	  NEXT_PASS (pass_early_vrp);
 	  NEXT_PASS (pass_merge_phi);
           NEXT_PASS (pass_dse);
-	  NEXT_PASS (pass_cd_dce, false /* update_address_taken_p */);
+	  NEXT_PASS (pass_cd_dce, false /* update_address_taken_p */, true /* remove_unused_locals */);
 	  NEXT_PASS (pass_phiopt, true /* early_p */);
 	  NEXT_PASS (pass_tail_recursion);
 	  NEXT_PASS (pass_if_to_switch);
@@ -225,10 +225,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_vrp, false /* final_p*/);
       NEXT_PASS (pass_array_bounds);
       NEXT_PASS (pass_dse);
-      NEXT_PASS (pass_dce);
-      /* pass_stdarg is always run and at this point we execute
-         TODO_remove_unused_locals to prune CLOBBERs of dead
-	 variables which are otherwise a churn on alias walkings.  */
+      NEXT_PASS (pass_dce, false /* update_address_taken_p */, true /* remove_unused_locals */);
       NEXT_PASS (pass_stdarg);
       NEXT_PASS (pass_call_cdce);
       NEXT_PASS (pass_cselim);
@@ -273,7 +270,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_asan);
       NEXT_PASS (pass_tsan);
       NEXT_PASS (pass_dse, true /* use DR analysis */);
-      NEXT_PASS (pass_dce);
+      NEXT_PASS (pass_dce, false /* update_address_taken_p */, false /* remove_unused_locals */);
       /* Pass group that runs when 1) enabled, 2) there are loops
 	 in the function.  Make sure to run pass_fix_loops before
 	 to discover/remove loops before running the gate function
@@ -355,7 +352,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_ccp, true /* nonzero_p */);
       NEXT_PASS (pass_warn_restrict);
       NEXT_PASS (pass_dse);
-      NEXT_PASS (pass_dce, true /* update_address_taken_p */);
+      NEXT_PASS (pass_dce, true /* update_address_taken_p */, true /* remove_unused_locals */);
       /* After late DCE we rewrite no longer addressed locals into SSA
 	 form if possible.  */
       NEXT_PASS (pass_forwprop);
diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index 69249c7..66612b5 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -2096,18 +2096,23 @@ public:
   opt_pass * clone () final override { return new pass_dce (m_ctxt); }
   void set_pass_param (unsigned n, bool param) final override
     {
-      gcc_assert (n == 0);
-      update_address_taken_p = param;
+      gcc_assert (n == 0 || n == 1);
+      if (n == 0)
+	update_address_taken_p = param;
+      else if (n == 1)
+	remove_unused_locals_p = param;
     }
   bool gate (function *) final override { return flag_tree_dce != 0; }
   unsigned int execute (function *) final override
     {
       return (tree_ssa_dce ()
+	      | (remove_unused_locals_p ? TODO_remove_unused_locals : 0)
 	      | (update_address_taken_p ? TODO_update_address_taken : 0));
     }
 
 private:
   bool update_address_taken_p;
+  bool remove_unused_locals_p = false;
 }; // class pass_dce
 
 } // anon namespace
@@ -2144,18 +2149,23 @@ public:
   opt_pass * clone () final override { return new pass_cd_dce (m_ctxt); }
   void set_pass_param (unsigned n, bool param) final override
     {
-      gcc_assert (n == 0);
-      update_address_taken_p = param;
+      gcc_assert (n == 0 || n == 1);
+      if (n == 0)
+	update_address_taken_p = param;
+      else if (n == 1)
+	remove_unused_locals_p = param;
     }
   bool gate (function *) final override { return flag_tree_dce != 0; }
   unsigned int execute (function *) final override
     {
       return (tree_ssa_cd_dce ()
+	      | (remove_unused_locals_p ? TODO_remove_unused_locals : 0)
 	      | (update_address_taken_p ? TODO_update_address_taken : 0));
     }
 
 private:
   bool update_address_taken_p;
+  bool remove_unused_locals_p = false;
 }; // class pass_cd_dce
 
 } // anon namespace
diff --git a/gcc/tree-stdarg.cc b/gcc/tree-stdarg.cc
index 1167fd9..33763cd 100644
--- a/gcc/tree-stdarg.cc
+++ b/gcc/tree-stdarg.cc
@@ -1114,7 +1114,7 @@ const pass_data pass_data_stdarg =
   ( PROP_cfg | PROP_ssa ), /* properties_required */
   PROP_gimple_lva, /* properties_provided */
   0, /* properties_destroyed */
-  TODO_remove_unused_locals, /* todo_flags_start */
+  0, /* todo_flags_start */
   0, /* todo_flags_finish */
 };