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GH-90043: Handle NaNs in `COMPARE_OP_FLOAT_JUMP` by brandtbucher · Pull Request #100278 · python/cpython · GitHub
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GH-90043: Handle NaNs in COMPARE_OP_FLOAT_JUMP #100278

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Merged
brandtbucher merged 5 commits into from
Dec 16, 2022
Merged

GH-90043: Handle NaNs in COMPARE_OP_FLOAT_JUMP #100278

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f0728cf
Handle NaNs in COMPARE_OP_FLOAT_JUMP
brandtbucher Nov 28, 2022
2665c9a
Remove NaN checks!
brandtbucher Nov 30, 2022
dba5894
Catch up with main
brandtbucher Nov 30, 2022
66d2d63
Catch up with main
brandtbucher Dec 15, 2022
9dc68aa
blurb add
brandtbucher Dec 15, 2022
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Handle NaNs in COMPARE_OP_FLOAT_JUMP
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@brandtbucher
brandtbucher committed Nov 28, 2022
commit f0728cf9c23935e4f51e848909581d3bd5a18083
11 changes: 6 additions & 5 deletions Python/bytecodes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2024,13 +2024,14 @@ dummy_func(
// Combined: COMPARE_OP (float ? float) + POP_JUMP_IF_(true/false)
DEOPT_IF(!PyFloat_CheckExact(left), COMPARE_OP);
DEOPT_IF(!PyFloat_CheckExact(right), COMPARE_OP);
STAT_INC(COMPARE_OP, hit);
double dleft = PyFloat_AS_DOUBLE(left);
double dright = PyFloat_AS_DOUBLE(right);
// 1 if <, 2 if ==, 4 if >; this matches when _to_jump_mask
int sign_ish = 2*(dleft > dright) + 2 - (dleft < dright);
DEOPT_IF(isnan(dleft), COMPARE_OP);
DEOPT_IF(isnan(dright), COMPARE_OP);
STAT_INC(COMPARE_OP, hit);
// 1 if <, 2 if ==, 4 if >, 8 if unordered; this matches when_to_jump_mask
int sign_ish = (+ 6 * (Py_IS_NAN(dleft) | Py_IS_NAN(dright))
+ 2 * (dleft > dright)
- 1 * (dleft < dright)
+ 2);
_Py_DECREF_SPECIALIZED(left, _PyFloat_ExactDealloc);
_Py_DECREF_SPECIALIZED(right, _PyFloat_ExactDealloc);
jump = sign_ish & when_to_jump_mask;
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11 changes: 6 additions & 5 deletions Python/generated_cases.c.h
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15 changes: 8 additions & 7 deletions Python/specialize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1927,12 +1927,13 @@ static int compare_masks[] = {
// 1-bit: jump if less than
// 2-bit: jump if equal
// 4-bit: jump if greater
[Py_LT] = 1 | 0 | 0,
[Py_LE] = 1 | 2 | 0,
[Py_EQ] = 0 | 2 | 0,
[Py_NE] = 1 | 0 | 4,
[Py_GT] = 0 | 0 | 4,
[Py_GE] = 0 | 2 | 4,
// 8-bit: jump if unordered
[Py_LT] = 1 | 0 | 0 | 0,
[Py_LE] = 1 | 2 | 0 | 0,
[Py_EQ] = 0 | 2 | 0 | 0,
[Py_NE] = 1 | 0 | 4 | 8,
[Py_GT] = 0 | 0 | 4 | 0,
[Py_GE] = 0 | 2 | 4 | 0,
};

void
Expand All @@ -1953,7 +1954,7 @@ _Py_Specialize_CompareOp(PyObject *lhs, PyObject *rhs, _Py_CODEUNIT *instr,
assert(oparg <= Py_GE);
int when_to_jump_mask = compare_masks[oparg];
if (next_opcode == POP_JUMP_IF_FALSE) {
when_to_jump_mask = (1 | 2 | 4) & ~when_to_jump_mask;
when_to_jump_mask = (1 | 2 | 4 | 8) & ~when_to_jump_mask;

@sweeneyde sweeneyde Dec 15, 2022

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I was skeptical of this at first, since I had thought about this as "use _Py_SwappedOp[op]", which would be wrong. But this looks correct -- it only swaps which branch to take.

@brandtbucher brandtbucher Dec 16, 2022

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Yep. The swapped ops used to be each others' bitwise inversions. That's no longer the case for the "unordered" bit, since NaNs only care if the operation is != or not.

}
if (Py_TYPE(lhs) != Py_TYPE(rhs)) {
SPECIALIZATION_FAIL(COMPARE_OP, compare_op_fail_kind(lhs, rhs));
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