On 2014/04/04 14:34:42, jbramley wrote:
On 2014/04/04 14:14:17, oetuaho-nv wrote:
> On 2014/04/04 09:43:05, jbramley wrote:
> > I can't find any use of vmsr that sets the rounding mode to anything
> > else. A few tests hit it, but the rounding mode is correct in every
> > case. Under what conditions can FPSCR be wrong here?
>
> Yes, it's not being set by other code generated by v8, but is there
> anything preventing other code that runs in the same execution context
> setting the FPSCR to another value?
Sort of, yes. AAPCS (the procedure-call standard) says that the
rounding-mode bits may be modified by "specific support functions that
affect the global state of the application". That is, we would have to
do it explicitly somewhere.
To me, that reads as you can't rely on the bits being set a certain way,
unless
I'm understanding "global state of the application" wrong somehow. Isn't
this
state shared with the entire renderer main thread in the case of Chromium,
for
example, which is running all sorts of code?
I'm also curious about the NaN bit, according to AAPCS bit 25 is one of the
"other" bits that must not be modified, yet it is modified in
VFPEnsureFPSCRState?
https://codereview.chromium.org/222403002/
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