1863435 - Faster allocation of small GC arrays

Status: RESOLVED FIXED

(Core :: JavaScript: WebAssembly, enhancement, P2)

Description

[Ben Visness [:bvisness]]

We currently malloc storage for all GC arrays and use instance calls for all allocations. We can speed this up using techniques like we now use for structs - some amount of inline data storage on WasmArrayObject, and a JIT allocation path for small nursery allocations.

Comment 1

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: Use better breakpoint code for arm64. r=mgaudet

On arm64, breakpoints occur before the instruction pointer moves to the next instruction. Stepping from this point just triggers the breakpoint again. However, if a breakpoint occurs with code 0xf000, lldb will manually advance past the breakpoint so stepping works as expected.

Comment 2

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: Implement inline data storage in gc arrays. r=rhunt,jonco

This only implements the internal storage and does not allocate arrays via JIT.

Depends on D196633

Comment 3

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: JIT allocation of gc arrays via Ion. r=rhunt,jonco

Depends on D196634

Comment 4

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: JIT allocation of gc arrays via baseline. r=rhunt

Depends on D196635

Comment 5

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: Read and write array elements using proper scaled indexes. r=rhunt,jseward

Depends on D196636

Comment 6

[Ben Visness [:bvisness]]

Attachment: WIP: Bug 1863435: Make array data pointers never null. r=rhunt

Depends on D196637

Comment 7

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: Remove wasm::StackMapBoolVector. r=rhunt

We currently do the rather strange process of building stack map info
in a vector, then creating a StackMap, then copying the information over.
This is particularly strange now that we store multiple kinds of entries
in our stack maps. We always know the size of the stack map anyway, so
this patch removes the vectors and builds the information in the stack
map directly.

However, the vector did serve the helpful purpose of avoiding memory
allocation in the common case of a small StackMap with no refs, which
does not need to be stored. StackMap has therefore been updated with new
APIs to help avoid memory allocation until actually necessary.

Depends on D196638

Comment 9

[Ben Visness [:bvisness]]

Attachment: Bug 1863435: Convert wasm struct objects to use TrailingArray. r=jonco

Zero-length arrays are disallowed by the C++ spec. The TrailingArray mixin
is a UB-free way of achieving the same data layout.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a06e0e423e3d
Use better breakpoint code for arm64. r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/e11d865508b4
Convert wasm struct objects to use TrailingArray. r=jonco
https://hg.mozilla.org/integration/autoland/rev/536bba21f186
Implement inline data storage in gc arrays. r=rhunt,jonco
https://hg.mozilla.org/integration/autoland/rev/0ed7433a0a3b
JIT allocation of gc arrays via Ion. r=rhunt,jonco
https://hg.mozilla.org/integration/autoland/rev/57c4fd85b686
JIT allocation of gc arrays via baseline. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/63ad7de808ca
Read and write array elements using proper scaled indexes. r=rhunt,jseward
https://hg.mozilla.org/integration/autoland/rev/fcafc196f2ce
Remove wasm::StackMapBoolVector. r=rhunt

Comment 11

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/a06e0e423e3d
https://hg.mozilla.org/mozilla-central/rev/e11d865508b4
https://hg.mozilla.org/mozilla-central/rev/536bba21f186
https://hg.mozilla.org/mozilla-central/rev/0ed7433a0a3b
https://hg.mozilla.org/mozilla-central/rev/57c4fd85b686
https://hg.mozilla.org/mozilla-central/rev/63ad7de808ca
https://hg.mozilla.org/mozilla-central/rev/fcafc196f2ce