| commit | 3ebcd0524debe45f3e6b922832839a5e7c3c8b23 | |
| author | Jan Oravec <jan@fb.com> | |
| Mon, 6 Apr 2020 14:51:01 +0000 (6 07:51 -0700) | ||
| committer | Facebook GitHub Bot <facebook-github-bot@users.noreply.github.com> | |
| Mon, 6 Apr 2020 14:54:11 +0000 (6 07:54 -0700) | ||
| tree | b1ff29f846533c20212b9cf49a07c4bfcf516d7a | treesnapshot (tar.gz zip) |
| parent | d97ea99fac56f338a209f62ccc5e79b1eabbafcc | commitdiff |
Optimize away undefined values from value component of TNull
Summary:
We emit a plenty of unnecessary `xor r, r`s to clear a register holding a value
component of TNull, especially when such value is used in a ternary or being
returned from a function.
Let's add a `ldundefq` to define such registers, use the existing register
allocator logic to issue these instructions right before non-optimizable use
(such as phijmp) and emit them as a noop.
Reviewed By: ricklavoie
Differential Revision: D20861091
fbshipit-source-id: dc8b24d332750c6f700d92585b3798a98aa945e2
Summary:
We emit a plenty of unnecessary `xor r, r`s to clear a register holding a value
component of TNull, especially when such value is used in a ternary or being
returned from a function.
Let's add a `ldundefq` to define such registers, use the existing register
allocator logic to issue these instructions right before non-optimizable use
(such as phijmp) and emit them as a noop.
Reviewed By: ricklavoie
Differential Revision: D20861091
fbshipit-source-id: dc8b24d332750c6f700d92585b3798a98aa945e2