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gh-129987: Disable GCC SLP autovectorization for the interpreter loop on x86-64 #132295

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Merged
merged 1 commit into from
Apr 9, 2025
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gh-129987: Disable GCC SLP autovectorization for the interpreter loop on x86-64 #132295

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13 changes: 12 additions & 1 deletion Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -948,7 +948,18 @@ _PyObjectArray_Free(PyObject **array, PyObject **scratch)
#include "generated_cases.c.h"
#endif

PyObject* _Py_HOT_FUNCTION
#if (defined(__GNUC__) && !defined(__clang__)) && defined(__x86_64__)
/*
* gh-129987: The SLP autovectorizer can cause poor code generation for opcode
* dispatch, negating any benefit we get from vectorization elsewhere in the
* interpreter loop.
*/
#define DONT_SLP_VECTORIZE __attribute__((optimize ("no-tree-slp-vectorize")))
#else
#define DONT_SLP_VECTORIZE
#endif

PyObject* _Py_HOT_FUNCTION DONT_SLP_VECTORIZE
_PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int throwflag)
{
_Py_EnsureTstateNotNULL(tstate);
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