emitIAS for fld and fstp

emitIAS for fld and fstp

BUG=none
R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=479e5633db43479c072256c0d7a9eb89acecf240

[jvoung (off chromium), 2014-10-08 18:00:54]

jvoung@chromium.org changed reviewers:
+ stichnot@chromium.org

[Jim Stichnoth, 2014-10-08 19:09:42]

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp
File src/IceInstX8632.cpp (left):

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp#oldcode...
src/IceInstX8632.cpp:1930: if (getDest() == NULL) {
I think "fstp st(0)" might possibly be used in the future, in the situation that
https://codereview.chromium.org/563303003/ addresses (but addresses in a
different way).

A better way might be to mark the fstp instruction as having side effects, and
allow dead-instruction elimination to "partially" delete the fstp instruction
(or any such instruction) by setting its Dest=NULL.

[jvoung (off chromium), 2014-10-08 20:51:47]

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp
File src/IceInstX8632.cpp (left):

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp#oldcode...
src/IceInstX8632.cpp:1930: if (getDest() == NULL) {
On 2014/10/08 19:09:41, stichnot wrote:
> I think "fstp st(0)" might possibly be used in the future, in the situation
that
> https://codereview.chromium.org/563303003/ addresses (but addresses in a
> different way).
> 
> A better way might be to mark the fstp instruction as having side effects, and
> allow dead-instruction elimination to "partially" delete the fstp instruction
> (or any such instruction) by setting its Dest=NULL.


Okay, so the benefit of that is it can avoid allocating a Variable for Dest if
it's unused / avoid conflicts.

I'll add back the check for getDest() == NULL and emit fstp st(0) then, and
leave a note?

[Jim Stichnoth, 2014-10-08 21:10:28]

lgtm

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp
File src/IceInstX8632.cpp (left):

https://codereview.chromium.org/634333002/diff/1/src/IceInstX8632.cpp#oldcode...
src/IceInstX8632.cpp:1930: if (getDest() == NULL) {
On 2014/10/08 20:51:47, jvoung wrote:
> On 2014/10/08 19:09:41, stichnot wrote:
> > I think "fstp st(0)" might possibly be used in the future, in the situation
> that
> > https://codereview.chromium.org/563303003/ addresses (but addresses in a
> > different way).
> > 
> > A better way might be to mark the fstp instruction as having side effects,
and
> > allow dead-instruction elimination to "partially" delete the fstp
instruction
> > (or any such instruction) by setting its Dest=NULL.
> 
> 
> Okay, so the benefit of that is it can avoid allocating a Variable for Dest if
> it's unused / avoid conflicts.
> 
> I'll add back the check for getDest() == NULL and emit fstp st(0) then, and
> leave a note?

Yes, thanks!

[jvoung (off chromium), 2014-10-09 04:05:32]

Committed patchset #3 (id:40001) manually as
479e5633db43479c072256c0d7a9eb89acecf240 (presubmit successful).