• H. S. Teoh (20/20) Mar 27 2014 Some time ago, Iain Buclaw kindly added non-asm implementations of math
• monarch_dodra (17/44) Mar 27 2014 //----

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

Some time ago, Iain Buclaw kindly added non-asm implementations of math
functions in std.math. However, CTFE still seems unable to correctly
evaluate certain functions like atan2:

	import std.math;
	enum x = atan2(1.0, 2.0);

Compiler output:

	/usr/src/d/phobos/std/math.d(856): Error: asm statements cannot be interpreted
at compile time
	/usr/src/d/phobos/std/math.d(917):        called from here: atan2(cast(real)y,
cast(real)x)
	test.d(2):        called from here: atan2(1.00000, 2.00000)

Looking at std/math.d, it appears that version=InlineAsm_X86_Any is
defined, which leads to the asm implementation of atan2, which CTFE
can't interpret.

However, right below that block is an else block containing a D
implementation of atan2 that AFAICT *can* be interpreted in CTFE.

So it would appear that version=InlineAsm_X86_Any should be suppressed
during CTFE? But I'm not sure how this could be done in the compiler.

In any case, it's an annoying limitation. :-(


T

-- 
Never step over a puddle, always step around it. Chances are that whatever made
it is still dripping.

"monarch_dodra" <monarchdodra gmail.com> writes:

On Thursday, 27 March 2014 at 18:18:25 UTC, H. S. Teoh wrote:
 Some time ago, Iain Buclaw kindly added non-asm implementations 
 of math
 functions in std.math. However, CTFE still seems unable to 
 correctly
 evaluate certain functions like atan2:

 	import std.math;
 	enum x = atan2(1.0, 2.0);

 Compiler output:

 	/usr/src/d/phobos/std/math.d(856): Error: asm statements 
 cannot be interpreted at compile time
 	/usr/src/d/phobos/std/math.d(917):        called from here: 
 atan2(cast(real)y, cast(real)x)
 	test.d(2):        called from here: atan2(1.00000, 2.00000)

 Looking at std/math.d, it appears that 
 version=InlineAsm_X86_Any is
 defined, which leads to the asm implementation of atan2, which 
 CTFE
 can't interpret.

 However, right below that block is an else block containing a D
 implementation of atan2 that AFAICT *can* be interpreted in 
 CTFE.

 So it would appear that version=InlineAsm_X86_Any should be 
 suppressed
 during CTFE? But I'm not sure how this could be done in the 
 compiler.

 In any case, it's an annoying limitation. :-(


 T

//----
auto atan(double x)
{
     version(InlineAsm_X86_Any)
     if (!__ctfe)
     {
         asm
         {
             ...
         }
         return;
     }

     Fall back non-InlineAsm_X86_Any and ctfe
}
//----

?