Wasmtime GitHub notifications bot (May 02 2023 at 02:07): Wasmtime GitHub notifications bot (May 02 2023 at 02:07):alexcrichton requested abrown for a review on PR #6323.
Wasmtime GitHub notifications bot (May 02 2023 at 02:07):alexcrichton opened PR #6323 from alexcrichton:x64-insertlane-sse2 to bytecodealliance:main:
This commit avoids the use of
pinsr*when SSE 4.1 is enabled by using alternative means of inserting values into vectors.<!--
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Wasmtime GitHub notifications bot (May 02 2023 at 02:07):alexcrichton requested wasmtime-compiler-reviewers for a review on PR #6323.
Wasmtime GitHub notifications bot (May 08 2023 at 17:09):abrown submitted PR review:
LGTM but see comments... (Sorry about the delay; I had my comments pending and forgot to submit it).
Wasmtime GitHub notifications bot (May 08 2023 at 17:09):abrown submitted PR review:
LGTM but see comments... (Sorry about the delay; I had my comments pending and forgot to submit it).
Wasmtime GitHub notifications bot (May 08 2023 at 17:09):abrown created PR review comment:
Before I look at the rest of the PR, I just wanted to recall something that bit me long ago: if moving from another XMM register, the bottom lane is merged with the rest; but if loading from memory, the upper lanes are zeroed. We just need to make sure Cranelift doesn't load-coalesce into this instruction.
Wasmtime GitHub notifications bot (May 08 2023 at 17:09):abrown created PR review comment:
The way this reads, we shuffle the lane:
n >> 2? Why? The shuffle immediates seem to line up with the originaln, notn >> 2.
Wasmtime GitHub notifications bot (May 08 2023 at 17:09):abrown created PR review comment:
So no load-coalescing after all, right?
Wasmtime GitHub notifications bot (May 08 2023 at 18:08):alexcrichton updated PR #6323.
Wasmtime GitHub notifications bot (May 08 2023 at 18:08):alexcrichton created PR review comment:
Indeed! The
x64_movss_regmovehelper has a doc block above it forx64_movsd_regmovecovering why load coalesing is disallowed there.
Wasmtime GitHub notifications bot (May 08 2023 at 18:09):alexcrichton created PR review comment:
I've updated the doc block above this to hopefully help clear up, but the low 2 bits of
nare where in a 32-bit lane the value goes and the upper 2 bits are which 32-bit lane is chosen for the finalpshufd(which the documentation was definitely not at all clearly saying)
Wasmtime GitHub notifications bot (May 08 2023 at 18:09):alexcrichton has enabled auto merge for PR #6323.
Wasmtime GitHub notifications bot (May 08 2023 at 19:25):alexcrichton merged PR #6323.
Last updated: Oct 23 2024 at 20:03 UTC