* Reworked the optimization of unused $parentfp for nested routines.

  - Do not remove the $parentfp parameter as was done in the previous optimization approach. Instead when $parentfp is unused to the following:
      - On the caller side: Omit passing the value for $parentfp for targets where tcgcallparanode.push_zero_sized_value_para=false (classic CPU targets). 
          Pass 0/nil as $parentfp for targets where tcgcallparanode.push_zero_sized_value_para=true;
      - On the callee side: Prevent allocation of registers/resources for $parentfp.
  - When possible keep $parentfp in a register.
  - Set the pio_nested_access flag in tprocinfo.set_needs_parentfp() to properly handle deep nesting levels;

git-svn-id: https://svn.freepascal.org/svn/fpc/trunk@45436 3ad0048d-3df7-0310-abae-a5850022a9f2

12 files changed, 150 insertions, 63 deletions

diff --git a/compiler/dbgbase.pas b/compiler/dbgbase.pas
index 2851aaddf2..af894216f2 100644
--- a/compiler/dbgbase.pas
+++ b/compiler/dbgbase.pas
@@ -103,7 +103,8 @@ implementation
 
     uses
       cutils,
-      verbose;
+      verbose,
+      cgbase;
 
 
     constructor TDebugInfo.Create;
@@ -430,7 +431,8 @@ implementation
           localvarsym :
             appendsym_localvar(list,tlocalvarsym(sym));
           paravarsym :
-            appendsym_paravar(list,tparavarsym(sym));
+            if tparavarsym(sym).localloc.loc<>LOC_VOID then
+              appendsym_paravar(list,tparavarsym(sym));
           constsym :
             appendsym_const(list,tconstsym(sym));
           typesym :
diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 0c2fb0c754..9dde2d1c99 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -2366,8 +2366,7 @@ implementation
               not is_nested_pd(def2))) or
             ((def1.typ=procdef) and                                 { d) }
              is_nested_pd(def1) and
-             ((not(po_delphi_nested_cc in def1.procoptions) and
-              (pio_needs_parentfp in tprocdef(def1).implprocoptions)) or
+             (not(po_delphi_nested_cc in def1.procoptions) or
               not is_nested_pd(def2))) or
             ((def1.typ=procvardef) and                              { e) }
              (is_nested_pd(def1)<>is_nested_pd(def2))) then
diff --git a/compiler/ncgcal.pas b/compiler/ncgcal.pas
index 0f964395f9..e9626eef43 100644
--- a/compiler/ncgcal.pas
+++ b/compiler/ncgcal.pas
@@ -41,6 +41,7 @@ interface
           procedure push_value_para;virtual;
           procedure push_formal_para;virtual;
           procedure push_copyout_para;virtual;abstract;
+          function maybe_push_unused_para:boolean;virtual;
        public
           tempcgpara : tcgpara;
 
@@ -60,6 +61,7 @@ interface
           procedure release_para_temps;
           procedure reorder_parameters;
           procedure freeparas;
+          function is_parentfp_pushed:boolean;
        protected
           retloc: tcgpara;
           paralocs: array of pcgpara;
@@ -169,6 +171,8 @@ implementation
       begin
         if not(left.location.loc in [LOC_CREFERENCE,LOC_REFERENCE]) then
           internalerror(200304235);
+        if maybe_push_unused_para then
+          exit;
         { see the call to keep_para_array_range in ncal: if that call returned
           true, we overwrite the resultdef of left with its original resultdef
           (to keep track of the range of the original array); we inserted a type
@@ -262,6 +266,9 @@ implementation
            not push_zero_sized_value_para then
           exit;
 
+        if maybe_push_unused_para then
+          exit;
+
         { Move flags and jump in register to make it less complex }
         if left.location.loc in [LOC_FLAGS,LOC_JUMP,LOC_SUBSETREG,LOC_CSUBSETREG,LOC_SUBSETREF,LOC_CSUBSETREF] then
           hlcg.location_force_reg(current_asmdata.CurrAsmList,left.location,left.resultdef,left.resultdef,false);
@@ -273,6 +280,8 @@ implementation
 
     procedure tcgcallparanode.push_formal_para;
       begin
+        if maybe_push_unused_para then
+          exit;
         { allow passing of a constant to a const formaldef }
         if (parasym.varspez=vs_const) and
            not(left.location.loc in [LOC_CREFERENCE,LOC_REFERENCE]) then
@@ -281,6 +290,35 @@ implementation
       end;
 
 
+    function tcgcallparanode.maybe_push_unused_para: boolean;
+      begin
+        { Check if the parameter is unused.
+          Only the $parentfp parameter is supported for now. }
+        result:=(vo_is_parentfp in parasym.varoptions) and (parasym.varstate<=vs_initialised);
+        if not result then
+          exit;
+        { The parameter is unused.
+          We can skip loading of the parameter when:
+            - the target does not strictly require all parameters (push_zero_sized_value_para = false)
+            and
+            - fixed stack is used
+              or the parameter is in a register
+              or the parameter is $parentfp. }
+        if not push_zero_sized_value_para and
+          (paramanager.use_fixed_stack or
+           (vo_is_parentfp in parasym.varoptions) or
+           (parasym.paraloc[callerside].Location^.Loc in [LOC_REGISTER,LOC_CREGISTER])) then
+          begin
+            { Skip loading }
+            parasym.paraloc[callerside].Location^.Loc:=LOC_VOID;
+            tempcgpara.Location^.Loc:=LOC_VOID;
+          end
+        else
+          { Load the dummy nil/0 value }
+          hlcg.a_load_const_cgpara(current_asmdata.CurrAsmList,left.resultdef,0,tempcgpara);
+      end;
+
+
     procedure tcgcallparanode.secondcallparan;
       var
          pushaddr: boolean;
@@ -909,6 +947,20 @@ implementation
        end;
 
 
+    function tcgcallnode.is_parentfp_pushed: boolean;
+      var
+        i : longint;
+      begin
+        for i:=0 to procdefinition.paras.Count-1 do
+          with tparavarsym(procdefinition.paras[i]) do
+            if vo_is_parentfp in varoptions then
+              begin
+                result:=paraloc[callerside].Location^.Loc in [LOC_REFERENCE,LOC_CREFERENCE];
+                exit;
+              end;
+        result:=false;
+      end;
+
 
     procedure tcgcallnode.pass_generate_code;
       var
@@ -1258,9 +1310,10 @@ implementation
                pop_parasize(0);
            end
          { frame pointer parameter is popped by the caller when it's passed the
-           Delphi way }
+           Delphi way and $parentfp is used }
          else if (po_delphi_nested_cc in procdefinition.procoptions) and
-           not paramanager.use_fixed_stack then
+            not paramanager.use_fixed_stack and
+            is_parentfp_pushed() then
            pop_parasize(sizeof(pint));
 
          if procdefinition.generate_safecall_wrapper then
diff --git a/compiler/ncgmem.pas b/compiler/ncgmem.pas
index 9dabcde485..39984f614d 100644
--- a/compiler/ncgmem.pas
+++ b/compiler/ncgmem.pas
@@ -170,9 +170,7 @@ implementation
             location_reset(location,LOC_REGISTER,def_cgsize(parentfpvoidpointertype));
             currpi:=current_procinfo;
             { load framepointer of current proc }
-            hsym:=tparavarsym(currpi.procdef.parast.Find('parentfp'));
-            if not assigned(hsym) then
-              internalerror(200309281);
+            hsym:=parentfpsym;
             if (currpi.procdef.owner.symtablelevel=parentpd.parast.symtablelevel) and (hsym.localloc.loc in [LOC_REGISTER,LOC_CREGISTER]) then
               location.register:=hsym.localloc.register
             else
diff --git a/compiler/ncgnstmm.pas b/compiler/ncgnstmm.pas
index b9688281b1..6afc96020e 100644
--- a/compiler/ncgnstmm.pas
+++ b/compiler/ncgnstmm.pas
@@ -105,7 +105,7 @@ implementation
           of the current routine (and hence it has not been moved into the
           nestedfp struct), get the original nestedfp parameter }
         useparentfppara:=not assigned(current_procinfo.procdef.parentfpstruct);
-        hsym:=tparavarsym(current_procinfo.procdef.parast.Find('parentfp'));
+        hsym:=parentfpsym;
         if current_procinfo.procdef.parast.symtablelevel>parentpd.parast.symtablelevel then
           useparentfppara:=
             useparentfppara or
diff --git a/compiler/ncgutil.pas b/compiler/ncgutil.pas
index b4d0063c24..85f0eb4b96 100644
--- a/compiler/ncgutil.pas
+++ b/compiler/ncgutil.pas
@@ -865,6 +865,13 @@ implementation
                       location_reset(vs.initialloc,LOC_REGISTER,OS_ADDR);
                       vs.initialloc.register:=NR_FRAME_POINTER_REG;
                     end
+                  { Unused parameters ($parentfp for now) need to be kept in the original location
+                    to prevent allocation of registers/resources for them. }
+                  else if (vs.varstate <= vs_initialised) and
+                    (vo_is_parentfp in vs.varoptions) then
+                    begin
+                      tparavarsym(vs).paraloc[calleeside].get_location(vs.initialloc);
+                    end
                   else
                     begin
                       { if an open array is used, also its high parameter is used,
@@ -1055,6 +1062,9 @@ implementation
           loadn:
             if (tloadnode(n).symtableentry.typ in [staticvarsym,localvarsym,paravarsym]) then
               add_regvars(rv^,tabstractnormalvarsym(tloadnode(n).symtableentry).localloc);
+          loadparentfpn:
+            if current_procinfo.procdef.parast.symtablelevel>tloadparentfpnode(n).parentpd.parast.symtablelevel then
+              add_regvars(rv^,tloadparentfpnode(n).parentfpsym.localloc);
           vecn:
             begin
               { range checks sometimes need the high parameter }
diff --git a/compiler/nld.pas b/compiler/nld.pas
index 719c18618d..3dc73417f1 100644
--- a/compiler/nld.pas
+++ b/compiler/nld.pas
@@ -357,8 +357,6 @@ implementation
                    if assigned(left) then
                      internalerror(200309289);
                    left:=cloadparentfpnode.create(tprocdef(symtable.defowner),lpf_forload);
-                   { we can't inline the referenced parent procedure }
-                   include(tprocdef(symtable.defowner).implprocoptions,pio_nested_access);
                    { reference in nested procedures, variable needs to be in memory }
                    { and behaves as if its address escapes its parent block         }
                    make_not_regable(self,[ra_different_scope]);
diff --git a/compiler/nmem.pas b/compiler/nmem.pas
index c5a83a6dca..f0a82ecd17 100644
--- a/compiler/nmem.pas
+++ b/compiler/nmem.pas
@@ -53,6 +53,10 @@ interface
          lpf_forload
        );
        tloadparentfpnode = class(tunarynode)
+       private
+          _parentfpsym: tparavarsym;
+          function getparentfpsym: tparavarsym;
+       public
           parentpd : tprocdef;
           parentpdderef : tderef;
           kind: tloadparentfpkind;
@@ -65,6 +69,7 @@ interface
           function pass_typecheck:tnode;override;
           function docompare(p: tnode): boolean; override;
           function dogetcopy : tnode;override;
+          property parentfpsym: tparavarsym read getparentfpsym;
        end;
        tloadparentfpnodeclass = class of tloadparentfpnode;
 
@@ -372,32 +377,9 @@ implementation
 
 
     function tloadparentfpnode.pass_typecheck:tnode;
-{$ifdef dummy}
-      var
-        currpi : tprocinfo;
-        hsym   : tparavarsym;
-{$endif dummy}
       begin
         result:=nil;
         resultdef:=parentfpvoidpointertype;
-{$ifdef dummy}
-        { currently parentfps are never loaded in registers (FK) }
-        if (current_procinfo.procdef.parast.symtablelevel<>parentpd.parast.symtablelevel) then
-          begin
-            currpi:=current_procinfo;
-            { walk parents }
-            while (currpi.procdef.owner.symtablelevel>parentpd.parast.symtablelevel) do
-              begin
-                currpi:=currpi.parent;
-                if not assigned(currpi) then
-                  internalerror(2005040602);
-                hsym:=tparavarsym(currpi.procdef.parast.Find('parentfp'));
-                if not assigned(hsym) then
-                  internalerror(2005040601);
-                hsym.varregable:=vr_none;
-              end;
-          end;
-{$endif dummy}
       end;
 
 
@@ -408,6 +390,17 @@ implementation
       end;
 
 
+    function tloadparentfpnode.getparentfpsym: tparavarsym;
+      begin
+        if not assigned(_parentfpsym) then
+          begin
+            _parentfpsym:=tparavarsym(current_procinfo.procdef.parast.Find('parentfp'));
+            if not assigned(_parentfpsym) then
+              internalerror(200309281);
+          end;
+        result:=_parentfpsym;
+      end;
+
 {*****************************************************************************
                              TADDRNODE
 *****************************************************************************}
diff --git a/compiler/pparautl.pas b/compiler/pparautl.pas
index 936806b141..f498cb56d8 100644
--- a/compiler/pparautl.pas
+++ b/compiler/pparautl.pas
@@ -156,7 +156,8 @@ implementation
               begin
                 vs:=cparavarsym.create('$parentfp',paranr,vs_value
                       ,parentfpvoidpointertype,[vo_is_parentfp,vo_is_hidden_para]);
-                vs.varregable:=vr_none;
+                { Mark $parentfp as used by default }
+                vs.varstate:=vs_read;
               end
             else
               begin
diff --git a/compiler/procinfo.pas b/compiler/procinfo.pas
index d627306b19..1e540c36f7 100644
--- a/compiler/procinfo.pas
+++ b/compiler/procinfo.pas
@@ -202,8 +202,9 @@ unit procinfo;
           procedure start_eh(list : TAsmList); virtual;
           { called to insert needed eh info into the exit code }
           procedure end_eh(list : TAsmList); virtual;
-          { Sets the pio_needs_parentfp flag for the current nested procedure and
-            all its parent procedures until parent_level }
+          { Sets the pio_needs_parentfp flag for the current nested procedure.
+            Sets both pio_needs_parentfp and pio_nested_access for all parent
+            procedures until parent_level }
           procedure set_needs_parentfp(parent_level: byte);
        end;
        tcprocinfo = class of tprocinfo;
@@ -442,11 +443,15 @@ implementation
           Internalerror(2020050302);
         if parent_level<normal_function_level then
           parent_level:=normal_function_level;
+        { Set pio_needs_parentfp for the current proc }
         pi:=Self;
-        repeat
-          include(pi.procdef.implprocoptions, pio_needs_parentfp);
-          pi:=pi.parent;
-        until pi.procdef.parast.symtablelevel<=parent_level;
+        include(pi.procdef.implprocoptions, pio_needs_parentfp);
+        { Set both pio_needs_parentfp and pio_nested_access for all parent procs until parent_level }
+        while pi.procdef.parast.symtablelevel>parent_level do
+          begin
+            pi:=pi.parent;
+            pi.procdef.implprocoptions:=pi.procdef.implprocoptions+[pio_needs_parentfp,pio_nested_access];
+          end;
       end;
 
 end.
diff --git a/compiler/psub.pas b/compiler/psub.pas
index e1c18b1101..a1983c7bcf 100644
--- a/compiler/psub.pas
+++ b/compiler/psub.pas
@@ -2309,8 +2309,6 @@ implementation
          parentfpinitblock: tnode;
          old_parse_generic: boolean;
          recordtokens : boolean;
-         parentfp_sym: TSymEntry;
-
       begin
          old_current_procinfo:=current_procinfo;
          old_block_type:=block_type;
@@ -2386,25 +2384,6 @@ implementation
          { parse the code ... }
          code:=block(current_module.islibrary);
 
-         { If this is a nested procedure which does not access its parent's frame
-           pointer, we can optimize it by removing the hidden $parentfp parameter.
-           Do not perform this for:
-             - targets which use a special struct to access parent's variables;
-             - pure assembler procedures (for compatibility with old code).
-         }
-         if not (target_info.system in systems_fpnestedstruct) and
-            is_nested_pd(procdef) and
-            not (pio_needs_parentfp in procdef.implprocoptions) and
-            not (po_assembler in procdef.procoptions) then
-           begin
-             exclude(procdef.procoptions, po_delphi_nested_cc);
-             parentfp_sym:=procdef.parast.Find('parentfp');
-             if parentfp_sym = nil then
-               Internalerror(2020050301);
-             procdef.parast.Delete(parentfp_sym);
-             procdef.calcparas;
-           end;
-
          if recordtokens then
            begin
              { stop token recorder for generic template }
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 78ed4ec8cb..ba7f1c1c1e 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -702,6 +702,8 @@ interface
        private
           procedure count_para(p:TObject;arg:pointer);
           procedure insert_para(p:TObject;arg:pointer);
+       protected
+          procedure handle_unused_paras(side: tcallercallee); virtual;
        end;
 
        tprocvardef = class(tabstractprocdef)
@@ -812,6 +814,7 @@ interface
          procedure SetIsEmpty(AValue: boolean);
          function GetHasInliningInfo: boolean;
          procedure SetHasInliningInfo(AValue: boolean);
+         procedure handle_unused_paras(side: tcallercallee); override;
        public
           messageinf : tmessageinf;
           dispid : longint;
@@ -5273,6 +5276,11 @@ implementation
       end;
 
 
+    procedure tabstractprocdef.handle_unused_paras(side: tcallercallee);
+    begin
+    end;
+
+
     procedure tabstractprocdef.calcparas;
       var
         paracount : longint;
@@ -5706,6 +5714,7 @@ implementation
               has_paraloc_info:=callbothsides
             else
               has_paraloc_info:=callerside;
+            handle_unused_paras(callerside);
           end;
         if (side in [calleeside,callbothsides]) and
            not(has_paraloc_info in [calleeside,callbothsides]) then
@@ -5718,6 +5727,7 @@ implementation
               has_paraloc_info:=callbothsides
             else
               has_paraloc_info:=calleeside;
+            handle_unused_paras(calleeside);
           end;
       end;
 
@@ -6011,6 +6021,45 @@ implementation
       end;
 
 
+    procedure tprocdef.handle_unused_paras(side: tcallercallee);
+      var
+        i : longint;
+      begin
+        { Optimize unused parameters by preventing loading them on the callee side
+          and, if possible, preventing passing them on the caller side.
+          The caller side optimization is handled by tcgcallparanode.maybe_push_unused_para().
+        }
+        if (proctypeoption = potype_exceptfilter) or
+          (po_assembler in procoptions) then
+          exit;
+        { Only $parentfp is optmized for now. }
+        if not is_nested_pd(self) then
+          exit;
+        { Handle unused parameters }
+        for i:=0 to paras.Count-1 do
+          with tparavarsym(paras[i]) do
+            if vo_is_parentfp in varoptions then
+              begin
+                if pio_needs_parentfp in implprocoptions then
+                  begin
+                    { If this routine is accessed from other nested routine,
+                      $parentfp must be in a memory location. }
+                    if pio_nested_access in implprocoptions then
+                      varregable:=vr_none;
+                  end
+                else
+                  begin
+                    { Mark $parentfp as unused, since it has vs_read by default }
+                    varstate:=vs_initialised;
+                    if side=calleeside then
+                      { Set LOC_VOID as the parameter's location on the callee side }
+                      paraloc[side].location^.Loc:=LOC_VOID;
+                    break;
+                  end;
+              end;
+      end;
+
+
     procedure tprocdef.Setinterfacedef(AValue: boolean);
       begin
         if not assigned(implprocdefinfo) then