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gh-119786: Add jit.md. Move adaptive.md to a section of interpreter.md. #127175

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Merged
iritkatriel merged 13 commits into from
Dec 6, 2024
Merged

gh-119786: Add jit.md. Move adaptive.md to a section of interpreter.md. #127175

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2fb97e3
gh-119786: add intro to adaptive.md. Update index headings
iritkatriel Nov 22, 2024
2414871
add content to tier2
iritkatriel Nov 22, 2024
e040267
review comments
iritkatriel Nov 23, 2024
e5802d7
add jit
iritkatriel Nov 28, 2024
0c96eb2
merge adaptive.md into interpreter.md
iritkatriel Dec 5, 2024
43aa0df
cache layouts
iritkatriel Dec 5, 2024
e7c3363
tier 2 --> jit
iritkatriel Dec 5, 2024
4731d94
remove adaptive.md
iritkatriel Dec 5, 2024
c4b288b
mike's comments
iritkatriel Dec 5, 2024
aced06a
Apply suggestions from code review
iritkatriel Dec 6, 2024
bc8a50b
interpreter jit is for debugging
iritkatriel Dec 6, 2024
3bbf6ee
Update InternalDocs/jit.md
iritkatriel Dec 6, 2024
acaef71
Merge branch 'main' into adaptive
iritkatriel Dec 6, 2024
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@iritkatriel
iritkatriel committed Dec 5, 2024
commit e040267dfd3a2312305c60980a7fa96c9c3c87f1
21 changes: 14 additions & 7 deletions InternalDocs/tier2.md
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Expand Up @@ -13,8 +13,9 @@ enables optimizations that span multiple instructions.
The program begins running in tier 1, until a `JUMP_BACKWARD` instruction
determines that it is `hot` because the counter in its
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[inline cache](interpreter.md#inline-cache-entries) indicates that is
executed more than some threshold number of times. It then calls the
function `_PyOptimizer_Optimize()` in
executed more than some threshold number of times (see
[`backoff_counter_triggers`](../Include/internal/pycore_backoff.h)).
It then calls the function `_PyOptimizer_Optimize()` in
[`Python/optimizer.c`](../Python/optimizer.c), passing it the current
[frame](frames.md) and instruction pointer. `_PyOptimizer_Optimize()`
constructs an object of type
Expand Down Expand Up @@ -46,17 +47,23 @@ each bytecode by an equivalent sequence of micro-ops
which is generated from [`Python/bytecodes.c`](../Python/bytecodes.c)).
The micro-op sequence is then optimized by
`_Py_uop_analyze_and_optimize` in
[`Python/optimizer_analysis.c`](../Python/optimizer_analysis.c).
[`Python/optimizer_analysis.c`](../Python/optimizer_analysis.c)
and a `_PyUOpExecutor_Type` is created to contain it.

## Running a uop executor
## Running a uop executor on the tier 2 interpreter

After a tier 1 `JUMP_BACKWARD` instruction invokes the uop optimizer
to create a tier 2 uop executor, it transfers control to this executor
via the `GOTO_TIER_TWO` macro, which jumps to `tier2_dispatch:` in
[`Python/ceval.c`](../Python/ceval.c), where there is a loops that
via the `GOTO_TIER_TWO` macro.

When tier 2 is enabled but the JIT is not (python was configured with
[`--enable-experimental-jit=interpreter`](https://docs.python.org/dev/using/configure.html#cmdoption-enable-experimental-jit)),
the executor jumps to `tier2_dispatch:` in
[`Python/ceval.c`](../Python/ceval.c), where there is a loop that
executes the micro-ops which are defined in
[`Python/executor_cases.c.h`](../Python/executor_cases.c.h).
This loop exits when an `_EXIT_TRACE` or `_DEOPT` uop is reached.
This loop exits when an `_EXIT_TRACE` or `_DEOPT` uop is reached,
and execution returns to teh tier 1 interpreter.

## Invalidating Executors

Expand Down