(In reply to Nathan Froyd [:froydnj] from comment #2)
(In reply to Chris Peterson [:cpeterson] from comment #1)
Once we move PGO profile generation to x86-64, we can retire the ARM emulators for good.
Just to be clear, are we using the x86-64 profiles for ARM, or are we using x86 profiles? Because the x86 profiles are likely to work much better due to bitnesses matching and therefore mangled names matching (more) closely. The same situation applies in reverse to a future AArch64 PGO build--we'd want to use x86-64 profiles there, not x86 ones.
We currently use the android-api-16 profile on both android-api-16 and android-aarch64 builds. There were perf wins for aarch64 according to talos even though the bitness doesn't match.
My intention here was to simply replace the android-api-16 profile generation stage with android-x86 profile generation for both, but once we have that running it shouldn't be hard to experiment with android-x86_64 for aarch64 to see if there's any additional improvement there.