ARM64: Avoid useRegister when useRegisterAtStart is good enough
Categories
(Core :: JavaScript: WebAssembly, enhancement, P3)
Tracking
()
People
(Reporter: lth, Assigned: lth)
References
(Blocks 1 open bug)
Details
Attachments
(1 file)
+++ This bug was initially created as a clone of Bug #1710024 +++
We use plain useRegister in the arm64 back-end when we could be using useRegisterAtStart, see eg the lowering of wasmShiftSimd128 with constant argument. This leads to more reg->reg moves and higher register pressure than necessary.
Clearly bug 1710024 addresses a related matter so there's some overlap between this bug and that, but also a separate investigation to do here.
|
Assignee | |
Comment 1•3 years ago
|
||
copysign: This does not need to reuse its input, so stop doing that.
Also a drive-by fix to prevent redundant register-to-register moves.
shift lanes by constant: This does not need to reuse its input, so
stop doing that.
replaceLane: This is optimal when it reuses its lhs as the output, so
do that. Remove the three-argument forms from the masm api, they are
only needed for loadLane, but load-lane can set up an lhs+output
argument just as easily.
loadLane: This is currently optimal when it reuses the lhs as the
output, but I did not change this because the work would have to be
undone again for bug 1706106, where we may be able to choose a
different codegen strategy. Left a comment in the code instead.
binary SIMD: removed a comment that points to something that is
actually bug 1701164, but the comment is not needed here.
Pushed by lhansen@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/38d302297da3 useRegisterAtStart when possible on ARM64. r=yury
|
||
Comment 3•3 years ago
|
||
| bugherder | ||
|
|
Assignee | |
Comment 4•3 years ago
|
||
(The leave-open came in with the bug cloning.)
Description
•