This optimization was added in bug 864218 to optimize asm.js-like code in Ion.
We're removing it now because:
WebAssembly happened and we've been focusing more on page load than on hot
It complicates the interpreter work because JSOP_SETALIASEDVAR can't do the
fast thing on singleton call objects and needs to fall back to an IC.
JSOP_SETALIASEDVAR and JSOP_INITALIASEDLEXICAL are currently marked as JOF_IC
so they always get a SetProp IC allocated for them. With this patch that no
The patch removes a lot of complexity.
It doesn't seem to affect Speedometer, Octane, other benchmarks.
Note that this also removes the EnvironmentCoordinateNameCache because
EnvironmentCoordinateName is now only called in debug-only or error-handling
code. I renamed it to EnvironmentCoordinateNameSlow to emphasize this.