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GH-109214: _SET_IP before _PUSH_FRAME (but not _POP_FRAME) #111001

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merged 3 commits into from
Oct 24, 2023
Merged

GH-109214: _SET_IP before _PUSH_FRAME (but not _POP_FRAME) #111001

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b1850df
Require a _SET_IP before _PUSH_FRAMEs
brandtbucher Oct 16, 2023
d83a7c8
Don't _SET_IP before _POP_FRAME
brandtbucher Oct 16, 2023
877f171
blurb add
brandtbucher Oct 16, 2023
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4 changes: 2 additions & 2 deletions Include/internal/pycore_opcode_metadata.h
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-10-16-15-51-37.gh-issue-109214.-RGTFH.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Remove unnecessary instruction pointer updates before returning from frames.
2 changes: 0 additions & 2 deletions Python/bytecodes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -803,7 +803,6 @@ dummy_func(
}

macro(RETURN_VALUE) =
_SAVE_CURRENT_IP + // Sets frame->prev_instr
_POP_FRAME;

inst(INSTRUMENTED_RETURN_VALUE, (retval --)) {
Expand All @@ -827,7 +826,6 @@ dummy_func(

macro(RETURN_CONST) =
LOAD_CONST +
_SAVE_CURRENT_IP + // Sets frame->prev_instr
_POP_FRAME;

inst(INSTRUMENTED_RETURN_CONST, (--)) {
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51 changes: 19 additions & 32 deletions Python/generated_cases.c.h
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14 changes: 6 additions & 8 deletions Python/optimizer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -679,7 +679,9 @@ translate_bytecode_to_trace(
case OPARG_BOTTOM: // Second half of super-instr
oparg = orig_oparg & 0xF;
break;
case OPARG_SET_IP: // op==_SET_IP; oparg=next instr
case OPARG_SET_IP: // uop=_SET_IP; oparg=next_instr-1
// The number of caches is smuggled in via offset:
assert(offset == _PyOpcode_Caches[_PyOpcode_Deopt[opcode]]);
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If this is always it, why do we need to smuggle it in via offset? Also it's beginning to look like the offset should just be made one larger in the code generator, so we can drop the ugly + 1 on line 654 above.

oparg = INSTR_IP(instr + offset, code);
uop = _SET_IP;
break;
Expand Down Expand Up @@ -827,11 +829,7 @@ remove_unneeded_uops(_PyUOpInstruction *trace, int trace_length)
bool need_ip = true;
for (int pc = 0; pc < trace_length; pc++) {
int opcode = trace[pc].opcode;
if (opcode == _SAVE_CURRENT_IP) {
// Special case: never remove preceding _SET_IP
last_set_ip = -1;
}
else if (opcode == _SET_IP) {
if (opcode == _SET_IP) {
if (!need_ip && last_set_ip >= 0) {
trace[last_set_ip].opcode = NOP;
}
Expand All @@ -843,8 +841,8 @@ remove_unneeded_uops(_PyUOpInstruction *trace, int trace_length)
break;
}
else {
// If opcode has ERROR or DEOPT, set need_up to true
if (_PyOpcode_opcode_metadata[opcode].flags & (HAS_ERROR_FLAG | HAS_DEOPT_FLAG)) {
// If opcode has ERROR or DEOPT, set need_ip to true
if (_PyOpcode_opcode_metadata[opcode].flags & (HAS_ERROR_FLAG | HAS_DEOPT_FLAG) || opcode == _PUSH_FRAME) {
need_ip = true;
}
}
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