Add support for SH4

src/greenlet/platform/switch_sh4_gcc.h

@@ -0,0 +1,36 @@
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+#define REGS_TO_SAVE "r8", "r9", "r10", "r11", "r13", \
+                     "fr12", "fr13", "fr14", "fr15"
+
+// r12 Global context pointer, GP
+// r14 Frame pointer, FP
+// r15 Stack pointer, SP
+
+static int
+slp_switch(void)
+{
+    int err;
+    void* fp;
+    int *stackref, stsizediff;
+    __asm__ volatile("" : : : REGS_TO_SAVE);
+    __asm__ volatile("mov.l r14, %0" : "=m"(fp) : :);
+    __asm__("mov %0, r15" : "=r"(stackref));
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile(
+            "add r15, %0\n"
+            "add r14, %0\n"
+            : /* no outputs */
+            : "r"(stsizediff));
+        SLP_RESTORE_STATE();
+        __asm__ volatile("mov r0, %0" : "=r"(err) : :);
+    }
+    __asm__ volatile("mov.l %0, r14" : : "m"(fp) :);
+    __asm__ volatile("" : : : REGS_TO_SAVE);
+    return err;
+}
+
+#endif

src/greenlet/slp_platformselect.h

@@ -64,6 +64,8 @@ extern "C" {
 # include "platform/switch_aarch64_gcc.h" /* LLVM Aarch64 ABI for Windows */
 #elif defined(__GNUC__) && defined(__loongarch64) && defined(__linux__)
 # include "platform/switch_loongarch64_linux.h" /* LoongArch64 */
+#elif defined(__GNUC__) && defined(__SH4__)
+# include "platform/switch_sh4_gcc.h" /* SH4 */
 #endif
 
 #ifdef __cplusplus