[cfe-dev] Fixed point and floating point comparision

[Gousemoodhin Nadaf via cfe-dev]

Hello Bevin,
Thanks for inputs,
Update: As per* N1169 4.1.4 (Type conversion, usual arithmetic conversions)*

* If one of the operands has a floating type and the other operand has a
fixed-point type, the fixedpoint operand is converted to the floating type
in the usual way*

I will implement this logic (conversion from a fixed point to floating
type), and will update further changes,

Regards,
Nadaf.

On Mon, Jul 6, 2020 at 4:36 AM Bevin Hansson <bevin.hansson at ericsson.com>
wrote:

> Hi,
>
>
>
> I’m afraid I don’t agree with your interpretation. The spec says “*The
> rounding* of conversions […] *is unspecified*”, not that the conversions
> themselves are.
>
>
>
> Floating-to-fixed point conversions just aren’t implemented yet, which is
> why it crashes. The support is still a bit experimental. I agree that it
> should not crash, though.
>
>
>
> I will leave some comments in the patch.
>
>
>
> / Bevin
>
>
>
> *From:* Gousemoodhin Nadaf <nadafgouse5 at gmail.com>
> *Sent:* July 05, 2020 9:35 PM
> *To:* Bevin Hansson <bevin.hansson at ericsson.com>
> *Cc:* cfe-dev at lists.llvm.org
> *Subject:* Re: [cfe-dev] Fixed point and floating point comparision
>
>
>
> Hello Bevin,
> As per N1169 4.1.4 (Type conversion, usual arithmetic conversions),
> conversions between the fixed point and floating point is unspecified. I
> believe before looking/checking for conversions, we have to handle
> unsupported conversions, if the conversion is not possible, we have to
> return NULL.
>
> Let me know your opinions.
>
> *Second patch updated:* Changed word from *"Comparision" *to*
> "Conversion", "Conversion"* is correct word to describe. This verified on
> the local build, it does not lead to a compiler crash.
>
> Regards,
> Nadaf.
>
>
>
> On Tue, Jun 16, 2020 at 5:17 AM Bevin Hansson <bevin.hansson at ericsson.com>
> wrote:
>
> Hi Gousemoodhin,
>
>
>
> I don't think 4.1.4 mentions anything about comparisons. The only mention
> of unspecified with floating point is "The rounding of conversions from a
> fixed-point type to a floating point type is unspecified."
>
>
>
> UsualArithmeticConversions and handleFixedPointConversion do not actually
> convert anything, they simply determine what the result type of the
> operation would be. So that would not be the place to 'determine'
> unspecified-ness; that would be a property of how the computation is
> performed in CodeGen or constant evaluation.
>
>
>
> I'm assuming you are trying to implement the floating point portions of
> N1169. A lot of the necessary boilerplate is not in place for that, as I
> haven't had time to look at it much quite yet.
>
>
>
> / Bevin
>
>
> ------------------------------
>
> *From:* cfe-dev <cfe-dev-bounces at lists.llvm.org> on behalf of
> Gousemoodhin Nadaf via cfe-dev <cfe-dev at lists.llvm.org>
> *Sent:* Saturday, June 13, 2020 6:22 AM
> *To:* cfe-dev at lists.llvm.org <cfe-dev at lists.llvm.org>
> *Subject:* [cfe-dev] Fixed point and floating point comparision
>
>
>
> Hello,
> When a comparison is made between the* fixed point and floating point*,
> the result is unspecified. Reference N1169 4.1.4 (Type conversion, usual
> arithmetic conversions).
>
> In code, for fixed-point number, handleFixedPointConversion()(SemaExpr.cpp)
> is called,  I need to return unspecified.
>
>
>
>
> *   handleFixedPointConversion()  {     if ((LHS is fixed point && RHS is
> floating point)  OR (RHS is fixed point && LHS is floating point)  )
> return unspecified.     }*
>
> please let me know If anyone has idea, how to return unspecified or handle
> an unspecified case in UsualArithmeticConversions.
>
> Regards,
> Nadaf.
>
>
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