From 45cd78643d8a874fb30047ea2448c979638d8ed8 Mon Sep 17 00:00:00 2001
From: Matt Page <mpage@meta.com>
Date: Tue, 8 Apr 2025 15:07:19 -0700
Subject: [PATCH] Disable GCC SLP autovectorization for the interpreter loop on
 x86-64

---
 Python/ceval.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/Python/ceval.c b/Python/ceval.c
index a59b2b7a16866d..47d068edac2743 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -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);