* use r7 instead of r11 as frame pointer on Darwin/iOS, and make sure r7

    always points to the previous r7 on the stack (with the saved return
    address coming right after it) so that the debugger and crashreporter
    can use it for backtraces as specified in the ABI
   o changed NR_FRAME_POINTER_REG and RS_FRAME_POINTER_REG from a symbolic
     into a typed constant, and added a new method to tprocinfo that can
     be used to initialze it (so it can be inited to r7/r11 depending on
     the target platform)
  * allow using r9 on Darwin, it was only used by the system on iOS up to
    2.x, which we no longer support
  * prefer using r9 and r12 before r4..r11 on Darwin, because they are
    volatile and hence do not have to be saved

git-svn-id: trunk@20661 -

compiler/arm/cgcpu.pas

@@ -209,17 +209,18 @@ unit cgcpu;
     procedure tarmcgarm.init_register_allocators;
       begin
         inherited init_register_allocators;
-        { currently, we save R14 always, so we can use it }
+        { currently, we always save R14, so we can use it }
         if (target_info.system<>system_arm_darwin) then
           rg[R_INTREGISTER]:=trgintcpu.create(R_INTREGISTER,R_SUBWHOLE,
-              [RS_R0,RS_R1,RS_R2,RS_R3,RS_R4,RS_R5,RS_R6,RS_R7,RS_R8,
-               RS_R9,RS_R10,RS_R12,RS_R14],first_int_imreg,[])
+              [RS_R0,RS_R1,RS_R2,RS_R3,RS_R12,RS_R4,RS_R5,RS_R6,RS_R7,RS_R8,
+               RS_R9,RS_R10,RS_R14],first_int_imreg,[])
         else
-          { r9 is not (always) available on Darwin according to the llvm code
-            generator. }
+          { r7 is not available on Darwin, it's used as frame pointer (always,
+            for backtrace support -- also in gcc/clang -> R11 can be used).
+            r9 is volatile }
           rg[R_INTREGISTER]:=trgintcpu.create(R_INTREGISTER,R_SUBWHOLE,
-              [RS_R0,RS_R1,RS_R2,RS_R3,RS_R4,RS_R5,RS_R6,RS_R7,RS_R8,
-               RS_R10,RS_R12,RS_R14],first_int_imreg,[]);
+              [RS_R0,RS_R1,RS_R2,RS_R3,RS_R9,RS_R12,RS_R4,RS_R5,RS_R6,RS_R8,
+               RS_R10,RS_R11,RS_R14],first_int_imreg,[]);
         rg[R_FPUREGISTER]:=trgcpu.create(R_FPUREGISTER,R_SUBNONE,
             [RS_F0,RS_F1,RS_F2,RS_F3,RS_F4,RS_F5,RS_F6,RS_F7],first_fpu_imreg,[]);
         { The register allocator currently cannot deal with multiple
@@ -1410,7 +1411,8 @@ unit cgcpu;
          firstfloatreg,lastfloatreg,
          r : byte;
          mmregs,
-         regs : tcpuregisterset;
+         regs, saveregs : tcpuregisterset;
+         r7offset,
          stackmisalignment : pint;
          postfix: toppostfix;
       begin
@@ -1446,41 +1448,91 @@ unit cgcpu;
             end;
             a_reg_alloc(list,NR_STACK_POINTER_REG);
             if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
-              begin
-                a_reg_alloc(list,NR_FRAME_POINTER_REG);
-                a_reg_alloc(list,NR_R12);
-
-                list.concat(taicpu.op_reg_reg(A_MOV,NR_R12,NR_STACK_POINTER_REG));
-              end;
+              a_reg_alloc(list,NR_FRAME_POINTER_REG);
             { save int registers }
             reference_reset(ref,4);
             ref.index:=NR_STACK_POINTER_REG;
             ref.addressmode:=AM_PREINDEXED;
             regs:=rg[R_INTREGISTER].used_in_proc-paramanager.get_volatile_registers_int(pocall_stdcall);
-            { the (old) ARM APCS requires saving both the stack pointer (to
-              crawl the stack) and the PC (to identify the function this
-              stack frame belongs to) -> also save R12 (= copy of R13 on entry)
-              and R15 -- still needs updating for EABI and Darwin, they don't
-              need that }
-            if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
-              regs:=regs+[RS_FRAME_POINTER_REG,RS_R12,RS_R14,RS_R15]
-            else
-              if (regs<>[]) or (pi_do_call in current_procinfo.flags) then
-                include(regs,RS_R14);
-            if regs<>[] then
-               begin
-                 for r:=RS_R0 to RS_R15 do
-                   if (r in regs) then
-                     inc(stackmisalignment,4);
-                 list.concat(setoppostfix(taicpu.op_ref_regset(A_STM,ref,R_INTREGISTER,R_SUBWHOLE,regs),PF_FD));
-               end;
+            if not(target_info.system in systems_darwin) then
+              begin
+                a_reg_alloc(list,NR_STACK_POINTER_REG);
+                if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
+                  begin
+                    a_reg_alloc(list,NR_R12);
+                    list.concat(taicpu.op_reg_reg(A_MOV,NR_R12,NR_STACK_POINTER_REG));
+                  end;
+                { the (old) ARM APCS requires saving both the stack pointer (to
+                  crawl the stack) and the PC (to identify the function this
+                  stack frame belongs to) -> also save R12 (= copy of R13 on entry)
+                  and R15 -- still needs updating for EABI and Darwin, they don't
+                  need that }
+                if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
+                  regs:=regs+[RS_FRAME_POINTER_REG,RS_R12,RS_R14,RS_R15]
+                else
+                  if (regs<>[]) or (pi_do_call in current_procinfo.flags) then
+                    include(regs,RS_R14);
+                if regs<>[] then
+                   begin
+                     for r:=RS_R0 to RS_R15 do
+                       if r in regs then
+                         inc(stackmisalignment,4);
+                     list.concat(setoppostfix(taicpu.op_ref_regset(A_STM,ref,R_INTREGISTER,R_SUBWHOLE,regs),PF_FD));
+                   end;
 
-            if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
+                if current_procinfo.framepointer<>NR_STACK_POINTER_REG then
+                  begin
+                    { the framepointer now points to the saved R15, so the saved
+                      framepointer is at R11-12 (for get_caller_frame) }
+                    list.concat(taicpu.op_reg_reg_const(A_SUB,NR_FRAME_POINTER_REG,NR_R12,4));
+                    a_reg_dealloc(list,NR_R12);
+                  end;
+              end
+            else
               begin
-                { the framepointer now points to the saved R15, so the saved
-                  framepointer is at R11-12 (for get_caller_frame) }
-                list.concat(taicpu.op_reg_reg_const(A_SUB,NR_FRAME_POINTER_REG,NR_R12,4));
-                a_reg_dealloc(list,NR_R12);
+                { always save r14 if we use r7 as the framepointer, because
+                  the parameter offsets are hardcoded in advance and always
+                  assume that r14 sits on the stack right behind the saved r7
+                }
+                if current_procinfo.framepointer=NR_FRAME_POINTER_REG then
+                  include(regs,RS_FRAME_POINTER_REG);
+                if (regs<>[]) or (pi_do_call in current_procinfo.flags) then
+                    include(regs,RS_R14);
+                if regs<>[] then
+                  begin
+                    { on Darwin, you first have to save [r4-r7,lr], and then
+                      [r8,r10,r11] and make r7 point to the previously saved
+                      r7 so that you can perform a stack crawl based on it
+                      ([r7] is previous stack frame, [r7+4] is return address
+                    }
+                    include(regs,RS_FRAME_POINTER_REG);
+                    saveregs:=regs-[RS_R8,RS_R10,RS_R11];
+                    r7offset:=0;
+                    for r:=RS_R0 to RS_R15 do
+                      if r in saveregs then
+                        begin
+                          inc(stackmisalignment,4);
+                          if r<RS_FRAME_POINTER_REG then
+                            inc(r7offset,4);
+                        end;
+                    { save the registers }
+                    list.concat(setoppostfix(taicpu.op_ref_regset(A_STM,ref,R_INTREGISTER,R_SUBWHOLE,saveregs),PF_FD));
+                    { make r7 point to the saved r7 (regardless of whether this
+                      frame uses the framepointer, for backtrace purposes) }
+                    if r7offset<>0 then
+                      list.concat(taicpu.op_reg_reg_const(A_ADD,NR_FRAME_POINTER_REG,NR_R13,r7offset))
+                    else
+                      list.concat(taicpu.op_reg_reg(A_MOV,NR_R7,NR_R13));
+                    { now save the rest (if any) }
+                    saveregs:=regs-saveregs;
+                    if saveregs<>[] then
+                      begin
+                        for r:=RS_R8 to RS_R11 do
+                          if r in saveregs then
+                            inc(stackmisalignment,4);
+                        list.concat(setoppostfix(taicpu.op_ref_regset(A_STM,ref,R_INTREGISTER,R_SUBWHOLE,saveregs),PF_FD));
+                      end;
+                  end;
               end;
 
             stackmisalignment:=stackmisalignment mod current_settings.alignment.localalignmax;
@@ -1564,6 +1616,7 @@ unit cgcpu;
          r,
          shift : byte;
          mmregs,
+         saveregs,
          regs : tcpuregisterset;
          stackmisalignment: pint;
          mmpostfix: toppostfix;
@@ -1649,22 +1702,47 @@ unit cgcpu;
               end;
 
             regs:=rg[R_INTREGISTER].used_in_proc-paramanager.get_volatile_registers_int(pocall_stdcall)        ;
-            if (pi_do_call in current_procinfo.flags) or (regs<>[]) then
+            if (pi_do_call in current_procinfo.flags) or
+               (regs<>[]) or
+               ((target_info.system in systems_darwin) and
+                (current_procinfo.framepointer<>NR_STACK_POINTER_REG)) then
               begin
                 exclude(regs,RS_R14);
                 include(regs,RS_R15);
+                if (target_info.system in systems_darwin) then
+                  include(regs,RS_FRAME_POINTER_REG);
               end;
-            { restore saved stack pointer to SP (R13) and saved lr to PC (R15).
-              The saved PC came after that but is discarded, since we restore
-              the stack pointer }
-            if (current_procinfo.framepointer<>NR_STACK_POINTER_REG) then
-              regs:=regs+[RS_FRAME_POINTER_REG,RS_R13,RS_R15];
 
+            if not(target_info.system in systems_darwin) then
+              begin
+                { restore saved stack pointer to SP (R13) and saved lr to PC (R15).
+                  The saved PC came after that but is discarded, since we restore
+                  the stack pointer }
+                if (current_procinfo.framepointer<>NR_STACK_POINTER_REG) then
+                  regs:=regs+[RS_FRAME_POINTER_REG,RS_R13,RS_R15];
+              end
+            else
+              begin
+                { restore R8-R11 already if necessary (they've been stored
+                  before the others) }
+                saveregs:=regs*[RS_R8,RS_R10,RS_R11];
+                if saveregs<>[] then
+                  begin
+                    reference_reset(ref,4);
+                    ref.index:=NR_STACK_POINTER_REG;
+                    ref.addressmode:=AM_PREINDEXED;
+                    for r:=RS_R8 to RS_R11 do
+                      if r in saveregs then
+                        inc(stackmisalignment,4);
+                    regs:=regs-saveregs;
+                  end;
+              end;
             for r:=RS_R0 to RS_R15 do
-              if (r in regs) then
+              if r in regs then
                 inc(stackmisalignment,4);
             stackmisalignment:=stackmisalignment mod current_settings.alignment.localalignmax;
-            if (current_procinfo.framepointer=NR_STACK_POINTER_REG) then
+            if (current_procinfo.framepointer=NR_STACK_POINTER_REG) or
+               (target_info.system in systems_darwin) then
               begin
                 LocalSize:=current_procinfo.calc_stackframe_size;
                 if (LocalSize<>0) or
@@ -1686,6 +1764,10 @@ unit cgcpu;
                       end;
                   end;
 
+                if (target_info.system in systems_darwin) and
+                   (saveregs<>[]) then
+                  list.concat(setoppostfix(taicpu.op_ref_regset(A_LDM,ref,R_INTREGISTER,R_SUBWHOLE,saveregs),PF_FD));
+
                 if regs=[] then
                   begin
                     if (current_settings.cputype<cpu_armv6) then

compiler/arm/cpubase.pas

@@ -269,9 +269,9 @@ unit cpubase;
       { Stack pointer register }
       NR_STACK_POINTER_REG = NR_R13;
       RS_STACK_POINTER_REG = RS_R13;
-      { Frame pointer register }
-      RS_FRAME_POINTER_REG = RS_R11;
-      NR_FRAME_POINTER_REG = NR_R11;
+      { Frame pointer register (initialized in tarmprocinfo.init_framepointer) }
+      RS_FRAME_POINTER_REG: tsuperregister = RS_NO;
+      NR_FRAME_POINTER_REG: tregister = NR_NO;
       { Register for addressing absolute data in a position independant way,
         such as in PIC code. The exact meaning is ABI specific. For
         further information look at GCC source : PIC_OFFSET_TABLE_REGNUM

compiler/arm/cpupara.pas

@@ -487,7 +487,16 @@ unit cpupara;
                      if paraloc^.loc=LOC_REFERENCE then
                        begin
                          paraloc^.reference.index:=NR_FRAME_POINTER_REG;
-                         inc(paraloc^.reference.offset,4);
+                         { on non-Darwin, the framepointer contains the value
+                           of the stack pointer on entry. On Darwin, the
+                           framepointer points to the previously saved
+                           framepointer (which is followed only by the saved
+                           return address -> framepointer + 4 = stack pointer
+                           on entry }
+                         if not(target_info.system in systems_darwin) then
+                           inc(paraloc^.reference.offset,4)
+                         else
+                           inc(paraloc^.reference.offset,8);
                        end;
                    end;
                  dec(paralen,tcgsize2size[paraloc^.size]);

compiler/arm/cpupi.pas

@@ -38,6 +38,7 @@ unit cpupi;
           // procedure after_pass1;override;
           procedure set_first_temp_offset;override;
           function calc_stackframe_size:longint;override;
+          procedure init_framepointer; override;
        end;
 
 
@@ -70,8 +71,10 @@ unit cpupi;
                 register (= last register in list above) -> + 4 }
               tg.setfirsttemp(-28-16+4)
             else
-              { on Darwin r9 is not usable -> one less register to save }
-              tg.setfirsttemp(-24-16+4)
+              { on Darwin first r4-r7,r14 are saved, then r7 is adjusted to
+                point to the saved r7, and next r8,r10,r11 gets saved -> -24
+                (r4-r6 and r8,r10,r11) }
+              tg.setfirsttemp(-24)
           end
         else
           tg.setfirsttemp(maxpushedparasize);
@@ -124,6 +127,21 @@ unit cpupi;
       end;
 
 
+    procedure tarmprocinfo.init_framepointer;
+      begin
+        if not(target_info.system in systems_darwin) then
+          begin
+            RS_FRAME_POINTER_REG:=RS_R11;
+            NR_FRAME_POINTER_REG:=NR_R11;
+          end
+        else
+          begin
+            RS_FRAME_POINTER_REG:=RS_R7;
+            NR_FRAME_POINTER_REG:=NR_R7;
+          end;
+      end;
+
+
 begin
    cprocinfo:=tarmprocinfo;
 end.

compiler/procinfo.pas

@@ -140,6 +140,9 @@ unit procinfo;
           { Allocate got register }
           procedure allocate_got_register(list: TAsmList);virtual;
 
+          { get frame pointer }
+          procedure init_framepointer; virtual;
+
           { Destroy the entire procinfo tree, starting from the outermost parent }
           procedure destroy_tree;
 
@@ -182,6 +185,7 @@ implementation
         procdef:=nil;
         para_stack_size:=0;
         flags:=[];
+        init_framepointer;
         framepointer:=NR_FRAME_POINTER_REG;
         maxpushedparasize:=0;
         { asmlists }
@@ -289,4 +293,11 @@ implementation
       end;
 
 
+    procedure tprocinfo.init_framepointer;
+      begin
+        { most targets use a constant, but some have a typed constant that must
+          be initialized }
+      end;
+
+
 end.

rtl/arm/arm.inc

@@ -101,7 +101,11 @@ end;
 {$define FPC_SYSTEM_HAS_GET_FRAME}
 function get_frame:pointer;assembler;nostackframe;
 asm
+{$ifndef darwin}
   mov    r0,r11
+{$else}
+  mov    r0,r7
+{$endif}
 end;
 {$ENDIF not INTERNAL_BACKTRACE}
 
@@ -109,7 +113,11 @@ end;
 function get_caller_addr(framebp:pointer):pointer;assembler;nostackframe;
 asm
   cmp r0,#0
+{$ifndef darwin}
   ldrne r0,[r0,#-4]
+{$else}
+  ldrne r0,[r0,#4]
+{$endif}
 end;
 
 
@@ -117,7 +125,11 @@ end;
 function get_caller_frame(framebp:pointer):pointer;assembler;nostackframe;
 asm
   cmp r0,#0
+{$ifndef darwin}
   ldrne r0,[r0,#-12]
+{$else}
+  ldrne r0,[r0]
+{$endif}
 end;