py/nlrmips: Add native NLR support for MIPS architecture.

This can be tested using ports/minimal and qemu:

    make CC=mips-linux-gnu-gcc-8

Then run with qemu-mips:

    stty raw opost -echo;
    QEMU_LD_PREFIX=/usr/mips-linux-gnu/ qemu-mips build/firmware.elf;
    sleep 1; reset

Signed-off-by: Jan Willeke <willeke@smartmote.de>

py/nlrmips.c

@@ -0,0 +1,86 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2017 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"
+
+#if MICROPY_NLR_MIPS
+
+__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr);
+
+__asm(
+    ".globl  nlr_push         \n"
+    "nlr_push:                \n"
+    ".ent    nlr_push         \n"
+    ".frame  $29, 0, $31      \n"
+    ".set    noreorder        \n"
+    ".cpload $25              \n"
+    ".set    reorder          \n"
+    "sw $31, 8($4)            \n"    /* is the offset of regs in nlr_buf_t */
+    "sw $30, 12($4)           \n"
+    "sw $29, 16($4)           \n"
+    "sw $28, 20($4)           \n"
+    "sw $23, 24($4)           \n"
+    "sw $22, 28($4)           \n"
+    "sw $21, 32($4)           \n"
+    "sw $20, 36($4)           \n"
+    "sw $19, 40($4)           \n"
+    "sw $18, 44($4)           \n"
+    "sw $17, 48($4)           \n"
+    "sw $16, 52($4)           \n"
+#ifdef __pic__
+    "la $25, nlr_push_tail    \n"
+#endif
+    "j nlr_push_tail          \n"
+    ".end nlr_push            \n"
+    );
+
+NORETURN void nlr_jump(void *val) {
+    MP_NLR_JUMP_HEAD(val, top)
+    __asm(
+        "move $4, %0    \n"
+        "lw $31, 8($4)  \n"
+        "lw $30, 12($4) \n"
+        "lw $29, 16($4) \n"
+        "lw $28, 20($4) \n"
+        "lw $23, 24($4) \n"
+        "lw $22, 28($4) \n"
+        "lw $21, 32($4) \n"
+        "lw $20, 36($4) \n"
+        "lw $19, 40($4) \n"
+        "lw $18, 44($4) \n"
+        "lw $17, 48($4) \n"
+        "lw $16, 52($4) \n"
+        "lui $2,1       \n"   // set return value 1
+        "j $31          \n"
+        "nop            \n"
+        :
+        : "r" (top)
+        :
+        );
+    MP_UNREACHABLE
+}
+
+#endif // MICROPY_NLR_MIPS