[PATCH] jscript: Force base type of _jsval_t to be ULONGLONG instead of double.

[Dmitry Timoshkov]

Gabriel Ivăncescu <gabrielopcode at gmail.com> wrote:

> On 24/03/2021 15:02, Dmitry Timoshkov wrote:
> > Gabriel Ivăncescu <gabrielopcode at gmail.com> wrote:
> > 
> >> Looks like a bug in Clang to me, although working around it is fine, but
> >> it's not my call.
> >>
> >> Nevertheless I think you should report it to Clang so they fix it.
> > 
> > Why do you think that it's a clang bug? Using fldl + fstpl to store and
> > fetch the double to/from the floating point stack is perfectly legitimate.
> > 
> 
> Well, because jsval_t is a union, not a double. Shouldn't assignment be 
> a bitwise copy? The compiler can't know what actual type is used by the 
> union here. Unless I misremember the C standard.

If I understand correctly, the compiler have chosen the memeber of
a maximal bits width and used it for a copy. That's unfortunate that
the chosen member happened to be of type 'double', and as a result
floating point instructions were used to perform the copying operation.

-- 
Dmitry.