[fpc-pascal] intel vs att asm (fstp instruction) (osx/clang features)

[Pierre Free Pascal]

I think the correct solution for you is to use explicit size information:

 

  FSTP SINGLE PTR [EDX]

  FSTP SINGLE PTR [EAX]

 

but

  FSTP [s]

and

  FSTP [c] 

would be even better, I don’t know if this syntax is Delphi compatible or not.

 

  It seems that indeed Free Pascal does not set the size of those instruction, 

but seems to use single as default size for internal code generation…

  When generating assembler file for GNU assembler or NASM,

it does not seem to print out this “assumed” size, which indeed

leads to a failure using –Anasm option on trunk compiler with i386-win32 target.

 

  My GNU as version 2.26 does not seem to need an explicit size,

but I don’t know what Xcode uses, isn’t it also a GNU assembler?

Could you tell us which assembler is used?

 

 

Pierre

  

 

De : fpc-pascal-bounces at lists.freepascal.org [mailto:fpc-pascal-bounces at lists.freepascal.org] De la part de Dmitry Boyarintsev
Envoyé : mercredi 4 mai 2016 02:28
À : FPC-Pascal users discussions
Objet : [fpc-pascal] intel vs att asm (fstp instruction) (osx/clang features)

 

Hello,

 

I'm dealing with the following code (from ZenGL library), targeting OSX

---------------

{$mode delphi}

 

procedure m_SinCos( Angle : Single; out s, c : Single ); assembler; 

asm

  FLD Angle

  FSINCOS

  FSTP [EDX]

  FSTP [EAX]

end;

 

var

  s,c: single;

begin

  m_SinCos(0,s,c);

end.

---------------

 

The latest Xcode 7.0 tools does recognize the generated assembler (fpc trunk):

---------

# [5] FLD Angle

          flds      8(%ebp)

# [6] FSINCOS

          fsincos

# [7] FSTP [EDX]

          fstp      (%edx)

# [8] FSTP [EAX]

          fstp      (%eax) 

---------

 

as a problem:

 

Assembling program

test.s:21:2: error: ambiguous instructions require an explicit suffix (could be 'fstps', 'fstpl', or 'fstpt')

        fstp    (%edx)

        ^

test.s:23:2: error: ambiguous instructions require an explicit suffix (could be 'fstps', 'fstpl', or 'fstpt')

        fstp    (%eax)

 

One interested could search the internet for the problem encountered with other platforms, and find out that the newer clang is somewhat backward incompatible.

 

My first attempt was to replace to put the suggested FSTPS instruction in place:

FSTPS [EDX]

However, the compiler stopped me, complaining about "FSTPS" is not a recognized instruction.

 

The next approach was to rewrite the function into at&t syntax. (The actual implementation could be found at sincos() of RTL math unit).

 

Is it a yet to be developed feature for FPC to satisfy demands of external tools relies on?

 

I presume since the compiler parses intel asm and translates it into at&t asm, it should take into consideration requirements of the latest osx building tools. 

Or is it already supported and I'm just missing a compiler switch?

 

thanks,

Dmitry

 

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