Skip to content

GH-91719: Make MSVC generate somewhat faster switch code #91718

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Apr 21, 2022
Merged

GH-91719: Make MSVC generate somewhat faster switch code #91718

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
ece341c
Make MSVC generate somewhat faster switch code
gvanrossum Apr 20, 2022
51ec108
Make opcode and use_tracing uint8_t
gvanrossum Apr 20, 2022
6603d85
Fix/move comment about opcode and switch
gvanrossum Apr 20, 2022
558d2c4
No need to check for opcode 255 any more
gvanrossum Apr 20, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion Include/cpython/pystate.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ typedef struct _PyCFrame {
* discipline and make sure that instances of this struct cannot
* accessed outside of their lifetime.
*/
int use_tracing;
uint8_t use_tracing; // 0 or 255 (or'ed into opcode, hence 8-bit type)
/* Pointer to the currently executing frame (it can be NULL) */
struct _PyInterpreterFrame *current_frame;
struct _PyCFrame *previous;
Expand Down
78 changes: 78 additions & 0 deletions Include/opcode.h
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

6 changes: 4 additions & 2 deletions Python/ceval.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1662,7 +1662,9 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
#ifdef Py_STATS
int lastopcode = 0;
#endif
int opcode; /* Current opcode */
// opcode is an 8-bit value to improve the code generated by MSVC
// for the big switch below (in combination with the EXTRA_CASES macro).
uint8_t opcode; /* Current opcode */
int oparg; /* Current opcode argument, if any */
_Py_atomic_int * const eval_breaker = &tstate->interp->ceval.eval_breaker;

Expand Down Expand Up @@ -5645,7 +5647,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
#if USE_COMPUTED_GOTOS
_unknown_opcode:
#else
default:
EXTRA_CASES // From opcode.h, a 'case' for each unused opcode
#endif
fprintf(stderr, "XXX lineno: %d, opcode: %d\n",
_PyInterpreterFrame_GetLine(frame), opcode);
Expand Down
7 changes: 7 additions & 0 deletions Tools/scripts/generate_opcode_h.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,13 @@ def main(opcode_py, outfile='Include/opcode.h'):
fobj.write("};\n")
fobj.write("#endif\n")

fobj.write("\n")
fobj.write("#define EXTRA_CASES \\\n")
for i, flag in enumerate(used):
if not flag:
fobj.write(f" case {i}: \\\n")
fobj.write(" ;\n")

fobj.write(footer)


Expand Down