[fpc-pascal] Procedural generics question

[Nico Neumann]

The TypeInfo function checks the code during run-time thus the generated
code is 'bloated'. Better use the compiler intrinsic GetTypeKind.

{$mode objfpc}

uses
   typinfo;

generic procedure Add<T>;
begin
    if GetTypeKind(T) = tkInteger then WriteLn('an integer');
    if GetTypeKind(T) = tkString then WriteLn('a string');
end;

begin
   specialize Add<Integer>;
   specialize Add<String>;
end.

for 'specialize Add<Integer>;' the following code is generated:

# [46] if GetTypeKind(T) = tkInteger then WriteLn('an integer');
call fpc_get_output
movq %rax,%rbx
leaq _$VT$_Ld1(%rip),%r8
movq %rbx,%rdx
movl $0,%ecx
call fpc_write_text_shortstr
call fpc_iocheck
movq %rbx,%rcx
call fpc_writeln_end
call fpc_iocheck
# [48] end;

Am Di., 25. Aug. 2020 um 23:54 Uhr schrieb Benito van der Zander via
fpc-pascal <fpc-pascal at lists.freepascal.org>:

> Hi,
>
> that is generating rather odd code (r40721)
>
> project1.lpr:9                            begin
> 0000000000401090 55                       push   %rbp
> 0000000000401091 4889e5                   mov    %rsp,%rbp
> 0000000000401094 488d6424f0               lea    -0x10(%rsp),%rsp
> 0000000000401099 48895df8                 mov    %rbx,-0x8(%rbp)
> project1.lpr:10                           if TypeInfo(T) =
> TypeInfo(Integer) then WriteLn('an integer');
> 000000000040109D 488d1584af0700           lea    0x7af84(%rip),%rdx
> # 0x47c028 <RTTI_$SYSTEM_$$_LONGINT>
> 00000000004010A4 488d057daf0700           lea    0x7af7d(%rip),%rax
> # 0x47c028 <RTTI_$SYSTEM_$$_LONGINT>
> 00000000004010AB 4839c2                   cmp    %rax,%rdx
> 00000000004010AE 752b                     jne    0x4010db
> <ADD$1$CRC713F463B+75>
> 00000000004010B0 e8cbcf0100               callq  0x41e080 <fpc_get_output>
> 00000000004010B5 4889c3                   mov    %rax,%rbx
> 00000000004010B8 488d15412f0600           lea    0x62f41(%rip),%rdx
> # 0x464000 <_$PROJECT1$_Ld1>
> 00000000004010BF 4889de                   mov    %rbx,%rsi
> 00000000004010C2 31ff                     xor    %edi,%edi
> 00000000004010C4 e867d30100               callq  0x41e430
> <fpc_write_text_shortstr>
> 00000000004010C9 e8d2700100               callq  0x4181a0 <fpc_iocheck>
> 00000000004010CE 4889df                   mov    %rbx,%rdi
> 00000000004010D1 e85ad20100               callq  0x41e330 <fpc_writeln_end>
> 00000000004010D6 e8c5700100               callq  0x4181a0 <fpc_iocheck>
> project1.lpr:11                           if TypeInfo(T) =
> TypeInfo(String) then WriteLn('a string');
> 00000000004010DB 488d0546af0700           lea    0x7af46(%rip),%rax
> # 0x47c028 <RTTI_$SYSTEM_$$_LONGINT>
> 00000000004010E2 488d1537b20700           lea    0x7b237(%rip),%rdx
> # 0x47c320 <RTTI_$SYSTEM_$$_SHORTSTRING>
> 00000000004010E9 4839d0                   cmp    %rdx,%rax
> 00000000004010EC 752b                     jne    0x401119
> <ADD$1$CRC713F463B+137>
> 00000000004010EE e88dcf0100               callq  0x41e080 <fpc_get_output>
> 00000000004010F3 4889c3                   mov    %rax,%rbx
> 00000000004010F6 488d15132f0600           lea    0x62f13(%rip),%rdx
> # 0x464010 <_$PROJECT1$_Ld2>
> 00000000004010FD 4889de                   mov    %rbx,%rsi
> 0000000000401100 31ff                     xor    %edi,%edi
> 0000000000401102 e829d30100               callq  0x41e430
> <fpc_write_text_shortstr>
> 0000000000401107 e894700100               callq  0x4181a0 <fpc_iocheck>
> 000000000040110C 4889df                   mov    %rbx,%rdi
> 000000000040110F e81cd20100               callq  0x41e330 <fpc_writeln_end>
> 0000000000401114 e887700100               callq  0x4181a0 <fpc_iocheck>
> project1.lpr:12                           end;
>
> The compiler should know everything about TypeInfo(T) and optimize it away
> where possible
>
> Cheers,
> Benito
> On 25.08.20 04:32, leledumbo via fpc-pascal wrote:
>
> I remember something like this in RTTI though but can't find it in your
>
> docs yet for generics.
>
> {$mode objfpc}
>
> uses
>   typinfo;
>
> generic procedure Add<T>;
> begin
>    if TypeInfo(T) = TypeInfo(Integer) then WriteLn('an integer');
>    if TypeInfo(T) = TypeInfo(String) then WriteLn('a string');
> end;
>
> begin
>   specialize Add<Integer>;
>   specialize Add<String>;
> end.
>
>
>
> --
> Sent from: http://free-pascal-general.1045716.n5.nabble.com/
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