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Merged
merged 17 commits into from
Sep 11, 2023
Merged

gh-109039: Branch prediction for Tier 2 interpreter #109038

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44db701
inst() and macro() may need cache size metadata
gvanrossum Sep 6, 2023
ff29ab3
Add cache entry to *POP_JUMP_IF_* instructions
gvanrossum Sep 6, 2023
ebc91a2
Fix test_dis (also fixes test_peepholer)
gvanrossum Sep 7, 2023
072bb38
Fix test_monitoring
gvanrossum Sep 7, 2023
896ae53
Include pycore_bitutils.h in instrumentation.c
gvanrossum Sep 7, 2023
0eb5b90
Follow likely jumps in trace
gvanrossum Sep 7, 2023
25bfb3d
Merge remote-tracking branch 'upstream/main' into count-branches
gvanrossum Sep 7, 2023
a9c0805
Require 16 iterations before optimizing
gvanrossum Sep 7, 2023
7dfb94c
Fix existing uops tests
gvanrossum Sep 7, 2023
73eb60f
Add test for branch prediction
gvanrossum Sep 7, 2023
fbd322a
Initialize POP_JUMP_IF* counters to 0x5555
gvanrossum Sep 7, 2023
ed045d7
Update counter in INSTRUMENTED_POP_JUMP_IF_FALSE
gvanrossum Sep 8, 2023
1850988
Simplify writing of _PyOpcode_Caches
gvanrossum Sep 8, 2023
4f1684c
Fix test_huntrleaks under -Xuops
gvanrossum Sep 8, 2023
cb2cf12
Fix test_dis under -Xuops
gvanrossum Sep 8, 2023
d74670c
Merge branch 'main' into count-branches
gvanrossum Sep 11, 2023
41463a5
Update magic number
gvanrossum Sep 11, 2023
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20 changes: 12 additions & 8 deletions Include/internal/pycore_opcode_metadata.h
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12 changes: 12 additions & 0 deletions Lib/opcode.py
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,18 @@
"counter": 1,
"version": 2,
},
"POP_JUMP_IF_TRUE": {
"counter": 1,
},
"POP_JUMP_IF_FALSE": {
"counter": 1,
},
"POP_JUMP_IF_NONE": {
"counter": 1,
},
"POP_JUMP_IF_NOT_NONE": {
"counter": 1,
},
}

_inline_cache_entries = {
Expand Down
219 changes: 111 additions & 108 deletions Lib/test/test_dis.py
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16 changes: 8 additions & 8 deletions Lib/test/test_monitoring.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1348,10 +1348,10 @@ def func():

self.check_events(func, recorders = JUMP_AND_BRANCH_RECORDERS, expected = [
('branch', 'func', 2, 2),
('branch', 'func', 3, 6),
('branch', 'func', 3, 4),
('jump', 'func', 6, 2),
('branch', 'func', 2, 2),
('branch', 'func', 3, 4),
('branch', 'func', 3, 3),
('jump', 'func', 4, 2),
('branch', 'func', 2, 2)])

Expand All @@ -1361,13 +1361,13 @@ def func():
('line', 'func', 2),
('branch', 'func', 2, 2),
('line', 'func', 3),
('branch', 'func', 3, 6),
('branch', 'func', 3, 4),
('line', 'func', 6),
('jump', 'func', 6, 2),
('line', 'func', 2),
('branch', 'func', 2, 2),
('line', 'func', 3),
('branch', 'func', 3, 4),
('branch', 'func', 3, 3),
('line', 'func', 4),
('jump', 'func', 4, 2),
('line', 'func', 2),
Expand Down Expand Up @@ -1400,8 +1400,8 @@ def func():
('line', 'func', 5),
('line', 'meth', 1),
('jump', 'func', 5, 5),
('jump', 'func', 5, '[offset=112]'),
('branch', 'func', '[offset=118]', '[offset=120]'),
('jump', 'func', 5, '[offset=114]'),
('branch', 'func', '[offset=120]', '[offset=122]'),
('line', 'get_events', 11)])

self.check_events(func, recorders = FLOW_AND_LINE_RECORDERS, expected = [
Expand All @@ -1416,8 +1416,8 @@ def func():
('line', 'meth', 1),
('return', None),
('jump', 'func', 5, 5),
('jump', 'func', 5, '[offset=112]'),
('branch', 'func', '[offset=118]', '[offset=120]'),
('jump', 'func', 5, '[offset=114]'),
('branch', 'func', '[offset=120]', '[offset=122]'),
('return', None),
('line', 'get_events', 11)])

Expand Down
47 changes: 34 additions & 13 deletions Python/bytecodes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2253,14 +2253,22 @@ dummy_func(
goto resume_frame;
}

inst(POP_JUMP_IF_FALSE, (cond -- )) {
inst(POP_JUMP_IF_FALSE, (unused/1, cond -- )) {
assert(PyBool_Check(cond));
JUMPBY(oparg * Py_IsFalse(cond));
int flag = Py_IsFalse(cond);
#if ENABLE_SPECIALIZATION
next_instr->cache = (next_instr->cache << 1) | flag;
#endif
JUMPBY(oparg * flag);
}

inst(POP_JUMP_IF_TRUE, (cond -- )) {
inst(POP_JUMP_IF_TRUE, (unused/1, cond -- )) {
assert(PyBool_Check(cond));
JUMPBY(oparg * Py_IsTrue(cond));
int flag = Py_IsTrue(cond);
#if ENABLE_SPECIALIZATION
next_instr->cache = (next_instr->cache << 1) | flag;
#endif
JUMPBY(oparg * flag);
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Don't you need also a SKIP_OVER the cache?

I'm guessing that could cause the assert(frame->prev_instr == instr); in _Py_call_instrumentation_jump to fail for the instrumented jumps.

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That skip over the cache is already generated -- see the corresponding code in generated_cases.c.h.

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You mean the "next_instr += 1;"? In all other cases there is an explicit SKIP_OVER(INLINE_CACHE_ENTRIES_...) in bytecodes.c.

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Those SKIP_OVER() calls are always followed by a DISPATCH() call (or maybe a goto).

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I see. Can we make the code generator emit SKIP_OVER(X) instead of next_instr += x;?

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We can, though IIRC Mark at some point objected to emitting macros. So I'd rather keep the status quo.

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@markshannon What is the reason not to emit macros?

A reason to emit them is so that they are implemented in one place, so if their implementation changes you only change there. Do we want to change the code generator (and to remember that we need to) every time the implementation of a macro like SKIP_OVER changes?

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Honestly I don't expect SKIP_OVER() to ever change. In hand-written code the macro expresses the intent better. But in generated code it just obscures what happens. I had to go to some lengths to change PEEK() and POKE() calls in the generated code to using stack_pointer[x] instead; I don't want to go back. If you still disagree, try engaging @markshannon.

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If you still disagree,

More like trying to understand than disagreeing.

try engaging @markshannon.

Yes I directed my previous comment to him.

}

op(IS_NONE, (value -- b)) {
Expand Down Expand Up @@ -3712,47 +3720,60 @@ dummy_func(
INSTRUMENTED_JUMP(next_instr-1, next_instr+1-oparg, PY_MONITORING_EVENT_JUMP);
}

inst(INSTRUMENTED_POP_JUMP_IF_TRUE, ( -- )) {
inst(INSTRUMENTED_POP_JUMP_IF_TRUE, (unused/1 -- )) {
PyObject *cond = POP();
assert(PyBool_Check(cond));
_Py_CODEUNIT *here = next_instr - 1;
int offset = Py_IsTrue(cond) * oparg;
int flag = Py_IsTrue(cond);
int offset = flag * oparg;
#if ENABLE_SPECIALIZATION
next_instr->cache = (next_instr->cache << 1) | flag;
#endif
INSTRUMENTED_JUMP(here, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
}

inst(INSTRUMENTED_POP_JUMP_IF_FALSE, ( -- )) {
inst(INSTRUMENTED_POP_JUMP_IF_FALSE, (unused/1 -- )) {
PyObject *cond = POP();
assert(PyBool_Check(cond));
_Py_CODEUNIT *here = next_instr - 1;
int offset = Py_IsFalse(cond) * oparg;
int flag = Py_IsFalse(cond);
int offset = flag * oparg;
INSTRUMENTED_JUMP(here, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
}

inst(INSTRUMENTED_POP_JUMP_IF_NONE, ( -- )) {
inst(INSTRUMENTED_POP_JUMP_IF_NONE, (unused/1 -- )) {
PyObject *value = POP();
_Py_CODEUNIT *here = next_instr-1;
_Py_CODEUNIT *here = next_instr - 1;
int flag = Py_IsNone(value);
int offset;
if (Py_IsNone(value)) {
if (flag) {
offset = oparg;
}
else {
Py_DECREF(value);
offset = 0;
}
#if ENABLE_SPECIALIZATION
next_instr->cache = (next_instr->cache << 1) | flag;
#endif
INSTRUMENTED_JUMP(here, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
}

inst(INSTRUMENTED_POP_JUMP_IF_NOT_NONE, ( -- )) {
inst(INSTRUMENTED_POP_JUMP_IF_NOT_NONE, (unused/1 -- )) {
PyObject *value = POP();
_Py_CODEUNIT *here = next_instr-1;
int offset;
if (Py_IsNone(value)) {
int flag = Py_IsNone(value);
if (flag) {
offset = 0;
}
else {
Py_DECREF(value);
offset = oparg;
}
#if ENABLE_SPECIALIZATION
next_instr->cache = (next_instr->cache << 1) | !flag;
#endif
INSTRUMENTED_JUMP(here, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
}

Expand Down
55 changes: 46 additions & 9 deletions Python/generated_cases.c.h
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17 changes: 15 additions & 2 deletions Tools/cases_generator/generate_cases.py
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Original file line number Diff line number Diff line change
Expand Up @@ -549,10 +549,23 @@ def write_metadata(self, metadata_filename: str, pymetadata_filename: str) -> No
"=",
";",
):
for name, _ in self.families.items():
family_member_names: set[str] = set()
for name, family in self.families.items():
family_member_names.update(family.members)
instr = self.instrs[name]
if instr.cache_offset > 0:
self.out.emit(f'[{name}] = {instr.cache_offset},')
self.out.emit(f"[{name}] = {instr.cache_offset},")
for instr in self.instrs.values():
if (
not instr.family
and instr.cache_offset
and instr.kind == "inst"
and not instr.name.startswith("INSTRUMENTED_")
):
self.out.emit(f"[{instr.name}] = {instr.cache_offset},")
for mac in self.macro_instrs.values():
if mac.name not in family_member_names and mac.cache_offset > 0:
self.out.emit(f"[{mac.name}] = {mac.cache_offset},")
# Irregular case:
self.out.emit('[JUMP_BACKWARD] = 1,')

Expand Down