717297 - IonMonkey: simplify the frame descriptor concept

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Chris Leary [:cdleary] (not checking bugmail)]

Attachment: WIP: x86 FD changes.

The frame descriptor, at present, describes the framePushed_ amount, which generally includes locals and arguments. However, the callee token may or may not be present above it (on the x86 stack) based on whether this is a JS-to-JS or JS-to-VM call. This makes like difficult for things like the invalidator, which gains control from either of these transition points.

This patch simplifies the concept of the frame descriptor to be the distance between the return addresses of frames, such that ((uint8 *) frame) + frame->frameSize() yields another (IonCommonFrameLayout *). The frame descriptor augments the framePushed_ amount appropriately at code generation time to account for the frame "prefix" fields that are also pushed onto the stack.