Does the current FPC compiler support  ARM inline assembler ?

If so what is the equivalent ARM command for {$ASMMODE intel}

Thanks
Brian

Vern via fpc-pascal schrieb am Do., 6.
Apr. 2023, 17:32:

Does the current FPC compiler support ARM inline assembler ?

Yes.

If so what is the equivalent ARM command for {$ASMMODE intel}

There is none, because only one syntax is supported.

Regards,
Sven

Not entirely true. Two ARM assembly syntaxes are supported: "divided" (pre-UAL) and unified (UAL).

Maybe not all aspects of either syntax are supported. Especially NEON/Advanced SIMD stuff might not be supported.

Best Regards,
Jeppe

After reading the FPC manual more closely , the correct compiler command is {$ASMMODE default} where/default /is the native system ... in this case Orange Pi arm64 and the compiler now allows accepting ARM assembler instructions.

However it won't allow referencing a Pascal variable.

Here is an example (32-bit) of x86 inline assembler that works correctly

procedure MSBitTest ( DataIn : longword);
var
  MSBit : longword;
begin
  asm
   bsr eax , DataIn
   mov MsBit , eax
  end;
end;

.......... the ARM version fails (similar code : ignore the fact it is the reverse of BSR) ... what am I missing ?

procedure MSBitTest ( DataIn : longword);
var
  MSBit : longword;
begin
  asm
   clz w4 , DataIn
   mov MsBit , w4
  end;
end;

Regards
Vern

ARM is a load/store architecture, which means it only supports operations on values loaded in registers. Local variables are always allocated on the stack in procedures/functions with inline assembler blocks, so you need to use the "str" instruction to store w4 into MsBit. "mov" only works for register-register transfers on ARM.

Jonas

Works now!

Many Thanks
Vern

Vern via fpc-pascal schrieb am Do., 6.
Apr. 2023, 19:06:

You don't need to use the $ASMMODE directive on non-x86 platforms, because the default syntax will always be selected. Also it's always possible to add assembly code.

Regards,
Sven