From 342524c31234981a48e52659d07ff2e52cbd81b4 Mon Sep 17 00:00:00 2001
From: florian <florian@freepascal.org>
Date: Wed, 2 Nov 2022 22:14:12 +0100
Subject: [PATCH] * run dead store elimination multiple times if needed

---
 compiler/optdeadstore.pas |  6 ++----
 compiler/psub.pas         | 13 ++++++++++---
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/compiler/optdeadstore.pas b/compiler/optdeadstore.pas
index 15cc52658c..72af98e611 100644
--- a/compiler/optdeadstore.pas
+++ b/compiler/optdeadstore.pas
@@ -31,7 +31,7 @@ unit optdeadstore;
     uses
       node;
 
-    function do_optdeadstoreelim(var rootnode : tnode) : tnode;
+    function do_optdeadstoreelim(var rootnode : tnode;changed: boolean) : tnode;
 
   implementation
 
@@ -106,9 +106,7 @@ unit optdeadstore;
       end;
 
 
-    function do_optdeadstoreelim(var rootnode: tnode): tnode;
-      var
-        changed: boolean;
+    function do_optdeadstoreelim(var rootnode: tnode;changed: boolean): tnode;
       begin
 {$ifdef EXTDEBUG_DEADSTORE}
         writeln('******************* Tree before deadstore elimination **********************');
diff --git a/compiler/psub.pas b/compiler/psub.pas
index 1637da941e..60702a347a 100644
--- a/compiler/psub.pas
+++ b/compiler/psub.pas
@@ -1294,15 +1294,22 @@ implementation
                        tabstractnormalvarsym(tloadnode(dfabuilder.nodemap[i]).symtableentry).noregvarinitneeded:=true
                    end;
                end;
+
+           if cs_opt_dead_store_eliminate in current_settings.optimizerswitches then
+             begin
+               changed:=false;
+               repeat
+                 do_optdeadstoreelim(code,changed);
+                 if changed then
+                   dfabuilder.redodfainfo(code);
+               until not(changed);
+             end;
          end
        else
          begin
            ConvertForLoops(code);
          end;
 
-       if (pi_dfaavailable in flags) and (cs_opt_dead_store_eliminate in current_settings.optimizerswitches) then
-         do_optdeadstoreelim(code);
-
        if (cs_opt_remove_empty_proc in current_settings.optimizerswitches) and
          (procdef.proctypeoption in [potype_operator,potype_procedure,potype_function]) and
          (code.nodetype=blockn) and (tblocknode(code).statements=nil) then