Wasmtime GitHub notifications bot (Jan 13 2025 at 20:16): Wasmtime GitHub notifications bot (Jan 13 2025 at 20:16):alexcrichton opened PR #9999 from alexcrichton:pulley-changing-stack to bytecodealliance:main:
This commit shrinks the size of the
PushFrameSaveandPopFrameRestorefunctions which are used in almost all wasm functions. Previously these instructions allowed for 32-bits of stack space in addition to saving/restoring all 32 X-registers. In reality though it's quite uncommon to need more than 16-bits of stack space and ABI-wise the most commonly saved registers are the upper 16 registers of the X register set.This commit therefore shrinks the frame size to 16 bits and only has the ability to save/restore the upper 16 X-registers. Note that any clobbered registers and frame sizes are still supported, they'll just use more pessimal encodings which aren't a single opcode. If a function uses >64KiB of stack space though it's probably not too important what the dispatch cost is at the beginning.
The overall result of this change is that each instruction shaves of 4 bytes (2 from the frame size and 2 from the registers being saved/restored). This results in a 4% faster execution time on the bz2 Sightglass benchmark, ~1% on pulldown-cmark, and while it shrinks
spidermonkey.cwasmslightly it's not significant.While here this commit also removes the Cranelift-unused instructions of
x{push,pop}{,_many}since theRegSettype was repurposed as anUpperRegSetinstead. It's possible to bring back these instructions but they're otherwise not used right now.<!--
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Wasmtime GitHub notifications bot (Jan 13 2025 at 20:16):alexcrichton requested fitzgen for a review on PR #9999.
Wasmtime GitHub notifications bot (Jan 13 2025 at 20:16):alexcrichton requested wasmtime-compiler-reviewers for a review on PR #9999.
Wasmtime GitHub notifications bot (Jan 13 2025 at 20:16):alexcrichton requested wasmtime-default-reviewers for a review on PR #9999.
Wasmtime GitHub notifications bot (Jan 13 2025 at 20:17):alexcrichton updated PR #9999.
Wasmtime GitHub notifications bot (Jan 13 2025 at 20:55):alexcrichton updated PR #9999.
Wasmtime GitHub notifications bot (Jan 13 2025 at 22:44):github-actions[bot] commented on PR #9999:
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Wasmtime GitHub notifications bot (Jan 14 2025 at 00:41):fitzgen submitted PR review:
Nice!
Wasmtime GitHub notifications bot (Jan 14 2025 at 01:18):alexcrichton requested wasmtime-core-reviewers for a review on PR #9999.
Wasmtime GitHub notifications bot (Jan 14 2025 at 01:18):alexcrichton requested pchickey for a review on PR #9999.
Wasmtime GitHub notifications bot (Jan 14 2025 at 01:18):alexcrichton updated PR #9999.
Wasmtime GitHub notifications bot (Jan 14 2025 at 01:18):alexcrichton has enabled auto merge for PR #9999.
Wasmtime GitHub notifications bot (Jan 14 2025 at 01:48):alexcrichton merged PR #9999.
Last updated: Jan 24 2025 at 00:11 UTC