Update 2025-04-13_16:25:39

venv/lib/python3.11/site-packages/greenlet/greenlet_slp_switch.hpp

@@ -0,0 +1,99 @@
+#ifndef GREENLET_SLP_SWITCH_HPP
+#define GREENLET_SLP_SWITCH_HPP
+
+#include "greenlet_compiler_compat.hpp"
+#include "greenlet_refs.hpp"
+
+/*
+ * the following macros are spliced into the OS/compiler
+ * specific code, in order to simplify maintenance.
+ */
+// We can save about 10% of the time it takes to switch greenlets if
+// we thread the thread state through the slp_save_state() and the
+// following slp_restore_state() calls from
+// slp_switch()->g_switchstack() (which already needs to access it).
+//
+// However:
+//
+// that requires changing the prototypes and implementations of the
+// switching functions. If we just change the prototype of
+// slp_switch() to accept the argument and update the macros, without
+// changing the implementation of slp_switch(), we get crashes on
+// 64-bit Linux and 32-bit x86 (for reasons that aren't 100% clear);
+// on the other hand, 64-bit macOS seems to be fine. Also, 64-bit
+// windows is an issue because slp_switch is written fully in assembly
+// and currently ignores its argument so some code would have to be
+// adjusted there to pass the argument on to the
+// ``slp_save_state_asm()`` function (but interestingly, because of
+// the calling convention, the extra argument is just ignored and
+// things function fine, albeit slower, if we just modify
+// ``slp_save_state_asm`()` to fetch the pointer to pass to the
+// macro.)
+//
+// Our compromise is to use a *glabal*, untracked, weak, pointer
+// to the necessary thread state during the process of switching only.
+// This is safe because we're protected by the GIL, and if we're
+// running this code, the thread isn't exiting. This also nets us a
+// 10-12% speed improvement.
+
+static greenlet::Greenlet* volatile switching_thread_state = nullptr;
+
+
+extern "C" {
+static int GREENLET_NOINLINE(slp_save_state_trampoline)(char* stackref);
+static void GREENLET_NOINLINE(slp_restore_state_trampoline)();
+}
+
+
+#define SLP_SAVE_STATE(stackref, stsizediff) \
+do {                                                    \
+    assert(switching_thread_state);  \
+    stackref += STACK_MAGIC;                 \
+    if (slp_save_state_trampoline((char*)stackref))    \
+        return -1;                                     \
+    if (!switching_thread_state->active()) \
+        return 1;                                      \
+    stsizediff = switching_thread_state->stack_start() - (char*)stackref; \
+} while (0)
+
+#define SLP_RESTORE_STATE() slp_restore_state_trampoline()
+
+#define SLP_EVAL
+extern "C" {
+#define slp_switch GREENLET_NOINLINE(slp_switch)
+#include "slp_platformselect.h"
+}
+#undef slp_switch
+
+#ifndef STACK_MAGIC
+#    error \
+        "greenlet needs to be ported to this platform, or taught how to detect your compiler properly."
+#endif /* !STACK_MAGIC */
+
+
+
+#ifdef EXTERNAL_ASM
+/* CCP addition: Make these functions, to be called from assembler.
+ * The token include file for the given platform should enable the
+ * EXTERNAL_ASM define so that this is included.
+ */
+extern "C" {
+intptr_t
+slp_save_state_asm(intptr_t* ref)
+{
+    intptr_t diff;
+    SLP_SAVE_STATE(ref, diff);
+    return diff;
+}
+
+void
+slp_restore_state_asm(void)
+{
+    SLP_RESTORE_STATE();
+}
+
+extern int slp_switch(void);
+};
+#endif
+
+#endif