* fixed returning small but "non-simple" records on ARM platforms that use

the old APCS calling convention (such as iOS): they are returned by
    reference

git-svn-id: trunk@20665 -

compiler/arm/cpupara.pas

@@ -55,7 +55,7 @@ unit cpupara;
     uses
        verbose,systems,cutils,
        rgobj,
-       defutil,symsym;
+       defutil,symsym,symtable;
 
 
     function tarmparamanager.get_volatile_registers_int(calloption : tproccalloption):tcpuregisterset;
@@ -202,10 +202,75 @@ unit cpupara;
 
 
     function tarmparamanager.ret_in_param(def : tdef;calloption : tproccalloption) : boolean;
+      var
+        i: longint;
+        sym: tsym;
+        fpufield: boolean;
       begin
         case def.typ of
           recorddef:
-            result:=def.size>4;
+            begin
+              result:=def.size>4;
+              if not result and
+                 (target_info.abi in [abi_default,abi_armeb]) then
+                begin
+                  { in case of the old ARM abi (APCS), a struct is returned in
+                    a register only if it is simple. And what is a (non-)simple
+                    struct:
+
+                    "A non-simple type is any non-floating-point type of size
+                     greater than one word (including structures containing only
+                     floating-point fields), and certain single-word structured
+                     types."
+                       (-- ARM APCS documentation)
+
+                    So only floating point types or more than one word ->
+                    definitely non-simple (more than one word is already
+                    checked above). This includes unions/variant records with
+                    overlaid floating point and integer fields.
+
+                    Smaller than one word struct types are simple if they are
+                    "integer-like", and:
+
+                    "A structure is termed integer-like if its size is less than
+                    or equal to one word, and the offset of each of its
+                    addressable subfields is zero."
+                      (-- ARM APCS documentation)
+
+                    An "addressable subfield" is a field of which you can take
+                    the address, which in practive means any non-bitfield.
+                    In Pascal, there is no way to express the difference that
+                    you can have in C between "char" and "int :8". In this
+                    context, we use the fake distinction that a type defined
+                    inside the record itself (such as "a: 0..255;") indicates
+                    a bitpacked field while a field using a different type
+                    (such as "a: byte;") is not.
+                  }
+                  for i:=0 to trecorddef(def).symtable.SymList.count-1 do
+                    begin
+                      sym:=tsym(trecorddef(def).symtable.SymList[i]);
+                      if sym.typ<>fieldvarsym then
+                        continue;
+                      { bitfield -> ignore }
+                      if (trecordsymtable(trecorddef(def).symtable).usefieldalignment=bit_alignment) and
+                         (tfieldvarsym(sym).vardef.typ in [orddef,enumdef]) and
+                         (tfieldvarsym(sym).vardef.owner.defowner=def) then
+                        continue;
+                      { all other fields must be at offset zero }
+                      if tfieldvarsym(sym).fieldoffset<>0 then
+                        begin
+                          result:=true;
+                          exit;
+                        end;
+                      { floating point field -> also by reference }
+                      if tfieldvarsym(sym).vardef.typ=floatdef then
+                        begin
+                          result:=true;
+                          exit;
+                        end;
+                    end;
+                end;
+            end;
           procvardef:
             if not tprocvardef(def).is_addressonly then
               result:=true