[fpc-pascal] FPC ARM inline Assembler

Jonas Maebe jonas at freepascal.org
Thu Apr 6 19:43:29 CEST 2023

On 06/04/2023 19:06, Vern via fpc-pascal wrote:
> .......... 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;

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.


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