1989118 - Share more EnterJit trampoline code

Status: NEW

(Core :: JavaScript Engine: JIT, enhancement, P3)

Description

[Iain Ireland [:iain]]

As part of the effort to remove the arguments rectifier, bug 1989107 factors out a shared architecture-independent section of generateEnterJit that handles pushing arguments. There's still a fair bit of unshared code in the architecture-specific implementations for handling OSR and doing the actual call, but the differences between architectures in that code are pretty sparse. We do some arch-specific hackery to push a fake return address, but that's bad for the branch predictor, so we should probably replace it with an actual call, similar to this code in BaselineCodeGen::emitResume.