1772987 - Save caller frame pointer in Wasm JitEntry stub

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P2)

Description

[Jan de Mooij [:jandem]]

Before we can add a frame pointer to Warp frames, we need to fix Wasm's JitEntry stub to not clobber the frame pointer. It currently does fp := sp in its prologue to make stack unwinding work.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1772987 part 1 - Add GenerateJitEntryEpilogue. r?rhunt!

A later patch will add an offsets argument to save the return offset.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1772987 part 2 - Rename unwoundIon* to unwoundJit*. r?rhunt!

The JitEntry stub is also used for calls from JS Baseline Interpreter/JIT code.

Depends on D148485

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1772987 part 3 - Save caller FP in JitEntry stub. r?rhunt!

The JitEntry stub clobbers the FP register in the prologue (to make stack unwinding work).
We need to change it to restore FP to allow adding frame pointers to Warp frames.

This patch changes the prologue to the standard frame prologue, and the epilogue
now stores the return offset to let the profiler correctly handle the instructions
between popping FP and returning.

ARM64 adds some complexity because the JIT ABI aligns the stack at the return address,
so we need to add a padding word to maintain 16-byte stack alignment. When we add the
callerFP to JitFrameLayout (similar to wasm::Frame) we can hopefully simplify this
a bit.

Depends on D148486

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6d3766652a6a
part 1 - Add GenerateJitEntryEpilogue. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/fa2fcbc1942c
part 2 - Rename unwoundIon* to unwoundJit*. r=rhunt
https://hg.mozilla.org/integration/autoland/rev/e32ea06d4f36
part 3 - Save caller FP in JitEntry stub. r=rhunt

Comment 5

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/6d3766652a6a
https://hg.mozilla.org/mozilla-central/rev/fa2fcbc1942c
https://hg.mozilla.org/mozilla-central/rev/e32ea06d4f36