[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

Walter Bright  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 CC||bugzi...@digitalmars.com
 Resolution|--- |DUPLICATE

--- Comment #13 from Walter Bright  ---


*** This issue has been marked as a duplicate of issue 5227 ***

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

Iain Buclaw  changed:

   What|Removed |Added

 CC||ibuc...@gdcproject.org

--- Comment #12 from Iain Buclaw  ---
This should probably be considered duplicate of issue 5227.

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

ki...@gmx.net changed:

   What|Removed |Added

 CC||ki...@gmx.net

--- Comment #11 from ki...@gmx.net ---
(In reply to uplink.coder from comment #10)
> (In reply to kinke from comment #9)
> > 
> > So how does newCTFE interact with CTFloat at the moment? This is an
> > important piece for cross-compilers. And is there an estimate for when
> > newCTFE will land?
> 
> It does currently not use CTFloat at all.
> It only implements add, sub, mul and div and mod for floats/doubles.
> As well as float <=> double <=> long/int casts.

[Sorry about hijacking this issue.] Okay, but as guys clearly expect most of
the math functionality to be available at CTFE too, newCTFE will eventually
have to feature a similar system of CTFE builtins (ddmd.builtin). Currently, it
plugs into function calls and tries to match the callee name in a map of
mangled name => CTFE implementation. The builtins are required for functions
whose source code isn't available for CTFE, such as compiler intrinsics, inline
assembly and C library functions.

So newCTFE discriminates between 32-bit float and 64-bit double but lacks
support for real_t, as opposed to the current interpreter, which uses real_t
exclusively (in RealExp). So the current floating-point builtin implementations
expect host/compiler-specific real_t values, but extending those to allow for
all 3 (float, double, real_t) should be straightforward.

newCTFE should at some point support real_t and use it to represent target
reals at compile-time. It's most likely the host real type, but it may also be
a software implementation as custom type with overloaded binops (GDC afaik,
possibly LDC at some point), with a specific size and alignment, and more
advanced functionality provided by helper struct CTFloat.

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[Issue 16474] CTFE pow

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #10 from uplink.co...@googlemail.com ---
(In reply to kinke from comment #9)
> 
> So how does newCTFE interact with CTFloat at the moment? This is an
> important piece for cross-compilers. And is there an estimate for when
> newCTFE will land?

It does currently not use CTFloat at all.
It only implements add, sub, mul and div and mod for floats/doubles.
As well as float <=> double <=> long/int casts.

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #9 from ki...@gmx.net ---
(In reply to uplink.coder from comment #7)
> (In reply to ZombineDev from comment #6)
> > Manu, you may be interested in trying LDC as it will soon support much more
> > intrinsics at CTFE than dmd. For reference:
> > https://github.com/ldc-developers/ldc/pull/2259 I'm not sure if specifically
> > the pow operator is supported (though pow is supported as a function call).

I started that work due to a recent ping of this issue and me accidentally
noticing it. ;)
So the pow operator is working with that PR for LDC; there a static assert in
the last line of the test.

> Do they interface with the CTFE engine ?
> That'd be crazy :)

I detect a few more key primitive functions (ldexp, isNaN, isInfinity,
isFinite...) as builtins and forward to proper implementations in CTFloat. I
also had to make std.math.exp2() CTFE-able for 80-bit reals by not using the
inline assembly code for CTFE. DMD may need a few more builtins or
CTFE-friendly Phobos implementations to get all of this working as well; I'll
open a DMD PR for the ones required by LDC.

So how does newCTFE interact with CTFloat at the moment? This is an important
piece for cross-compilers. And is there an estimate for when newCTFE will land?

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #8 from ZombineDev  ---
I don't think so, but see the PR for yourself ;)

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #7 from uplink.co...@googlemail.com ---
(In reply to ZombineDev from comment #6)
> Manu, you may be interested in trying LDC as it will soon support much more
> intrinsics at CTFE than dmd. For reference:
> https://github.com/ldc-developers/ldc/pull/2259 I'm not sure if specifically
> the pow operator is supported (though pow is supported as a function call).

Do they interface with the CTFE engine ?
That'd be crazy :)

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

ZombineDev  changed:

   What|Removed |Added

 CC||petar.p.ki...@gmail.com

--- Comment #6 from ZombineDev  ---
Manu, you may be interested in trying LDC as it will soon support much more
intrinsics at CTFE than dmd. For reference:
https://github.com/ldc-developers/ldc/pull/2259 I'm not sure if specifically
the pow operator is supported (though pow is supported as a function call).

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #5 from Manu  ---
True, but that could still be a long way off, and this should have already been
working like, 10 years ago... it'd be good to have a default fix in existing
ctfe code.

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #4 from uplink.co...@googlemail.com ---
newCTFE is eventually going to fix that.
and other compile-time floating-point issues as well.

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #3 from Manu  ---
Come on... surely it's reasonable to expect all builtin operators should work
at ctfe!! ;)

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

--- Comment #2 from Manu  ---
Sure, or reals, whatever precision the compiler does floating point constant
folding would be fine.

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[Issue 16474] CTFE pow

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https://issues.dlang.org/show_bug.cgi?id=16474

uplink.co...@googlemail.com changed:

   What|Removed |Added

 CC||uplink.co...@googlemail.com

--- Comment #1 from uplink.co...@googlemail.com ---
are 64bit floating point operations good enough for you ?
(And anyone else)
If so the fix is rather straight-forward.

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