py/nlrxtensa: Convert from assembler to C file with inline asm.

nlr_jump is a little bit inefficient because it now saves a register to
the stack.

Author: dpgeorge

py/nlrxtensa.S

@@ -0,0 +1,103 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2014-2017 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/mpstate.h"
+#include "py/nlr.h"
+
+#if !MICROPY_NLR_SETJMP && defined(__xtensa__)
+
+#undef nlr_push
+
+// Xtensa calling conventions:
+//  a0 = return address
+//  a1 = stack pointer
+//  a2 = first arg, return value
+//  a3-a7 = rest of args
+
+unsigned int nlr_push(nlr_buf_t *nlr) {
+
+    __asm volatile (
+    "s32i.n  a0, a2, 8          \n" // save regs...
+    "s32i.n  a1, a2, 12         \n"
+    "s32i.n  a8, a2, 16         \n"
+    "s32i.n  a9, a2, 20         \n"
+    "s32i.n  a10, a2, 24        \n"
+    "s32i.n  a11, a2, 28        \n"
+    "s32i.n  a12, a2, 32        \n"
+    "s32i.n  a13, a2, 36        \n"
+    "s32i.n  a14, a2, 40        \n"
+    "s32i.n  a15, a2, 44        \n"
+    "j      nlr_push_tail       \n" // do the rest in C
+    );
+
+    return 0; // needed to silence compiler warning
+}
+
+__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
+    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
+    nlr->prev = *top;
+    *top = nlr;
+    return 0; // normal return
+}
+
+void nlr_pop(void) {
+    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
+    *top = (*top)->prev;
+}
+
+NORETURN void nlr_jump(void *val) {
+    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
+    nlr_buf_t *top = *top_ptr;
+    if (top == NULL) {
+        nlr_jump_fail(val);
+    }
+
+    top->ret_val = val;
+    *top_ptr = top->prev;
+
+    __asm volatile (
+    "mov.n   a2, %0             \n" // a2 points to nlr_buf
+    "l32i.n  a0, a2, 8          \n" // restore regs...
+    "l32i.n  a1, a2, 12         \n"
+    "l32i.n  a8, a2, 16         \n"
+    "l32i.n  a9, a2, 20         \n"
+    "l32i.n  a10, a2, 24        \n"
+    "l32i.n  a11, a2, 28        \n"
+    "l32i.n  a12, a2, 32        \n"
+    "l32i.n  a13, a2, 36        \n"
+    "l32i.n  a14, a2, 40        \n"
+    "l32i.n  a15, a2, 44        \n"
+    "movi.n a2, 1               \n" // return 1, non-local return
+    "ret.n                      \n" // return
+    :                               // output operands
+    : "r"(top)                      // input operands
+    :                               // clobbered registers
+    );
+
+    for (;;); // needed to silence compiler warning
+}
+
+#endif // !MICROPY_NLR_SETJMP && defined(__xtensa__)