gh-111786: Use separate opcode vars for Tier 1 and Tier 2

[mdboom]

Suggested by @neonene: #111786 (comment)

This makes Windows about 3% faster on pyperformance benchmarks. See analysis here

• Issue: PGO build broken on Windows #111786

[gvanrossum]

Nice, looks very straightforward.

Though based on our offline conversation, did you find out whether Windows PGO uses -E?

[gvanrossum]

Heh, I would have kept the comments at the same column, so you don't appear to be editing the oparg line. :-)

[mdboom]

Sure -- I think my editor did something magical.

[mdboom]

Though based on our offline conversation, did you find out whether Windows PGO uses -E?

I don't know, but I think that's orthogonal to this. Currently on the benchmarking infrastructure, we only pass the PYTHON_UOPS env variable to pyperformance, so it definitely has no effect during build. Independently of this, I measured what happens when you force Tier 2 on during the build, and it is about 1% faster.

[gvanrossum]

Though based on our offline conversation, did you find out whether Windows PGO uses -E?

I don't know, but I think that's orthogonal to this. Currently on the benchmarking infrastructure, we don't pass the PYTHON_UOPS env variable to pyperformance, so it definitely has no effect during build.

Ah, sorry. Should I merge this then?

Independently of this, I measured what happens when you force Tier 2 on during the build, and it is about 1% faster.

1% faster than without Tier 2, or 1% faster than main?

[mdboom]

Though based on our offline conversation, did you find out whether Windows PGO uses -E?

I don't know, but I think that's orthogonal to this. Currently on the benchmarking infrastructure, we don't pass the PYTHON_UOPS env variable to pyperformance, so it definitely has no effect during build.

Ah, sorry. Should I merge this then?

Yeah, I think that's fine.

Independently of this, I measured what happens when you force Tier 2 on during the build, and it is about 1% faster.

1% faster than without Tier 2, or 1% faster than main?

When you turn Tier 2 on during build (PGO collection), it's 1% faster than if you don't. (Using Tier 2 at runtime in both cases).

[gvanrossum]

When you turn Tier 2 on during build (PGO collection), it's 1% faster than if you don't. (Using Tier 2 at runtime in both cases).

That's great news!