Re: Code Statement

[Simon Wright <simon@pushface.org>]

anon@att.net writes:

> As for the example supplied I decide use the intel "nop" for simplicity
> instead of using the codes for the attached processor.

Ah! I see what you meant by "special project".

> I prefer to use the Code Statement like the System.Machine_Code in SUN, 
> instead of using the inline-assembler of gnat\gcc. which forces the 
> following type of statements for non-native processors:
>
>     ASM ( " .byte 0x90" ) ; -- intel x86 nop
>     ASM ( " .byte 0x02" ) ; -- attach processor instruction "Load R2"
>     ...
>
> And using the code statement allows the Ada compiler to emulate a small 
> limited assembler without all of the work\time in rewriting\expanding 
> the gcc "AS" to include the new processor.
>
> So, I see no problem in using code statement except for creating or 
> expand and recompiling the "system.machine_code" package. Unless Adacore 
> has crippled gnat's code statement routines.

I'm not sure what http://www.adaic.com/standards/05rm/html/RM-13-8.html
(2) means; does it give you a licence to use any type you lke? seems
unlikely.

> Now, the RM 13.8 (2), says that the code statement is qualified_expression 
> so what the problem.  In Gnat, the ASM routines are handled by the 
> "Expand_Asm_Call" procedure ("exp_code" package) which expands the ASM 
> statement into a qualified_expression.  Also, "P_Code_Statement" ("par-ch13" 
> package) directly processes code_statements as an qualified_expression.  
> Afterwards, the "Analyze_Code_Statement" ("sem-ch13" package)  analyzes 
> should handle the code statements but this routine is where the error 
> message is generated.

I expect the compiler is written to expect System.Machine_Code.Asm_Insn
of the specific type defined in System.Machine_Code.

You could write
   Asm_Insn'(Asm (".byte 0x90"));
but it hardly seems worth the trouble. AdaCore have provided this as a 
"feature" I think -- see the GNAT RM, 
http://gcc.gnu.org/onlinedocs/gcc-4.5.0/gnat_rm/Machine-Code-Insertions.html