lib/utils/gchelper_m3: Add license header and clean up code.

This file generates the same code with the cortex-m3 and cortex-m4
assembler directive, so use cortex-m3 to support more CPUs.

lib/utils/gchelper_m3.s

@@ -1,14 +1,40 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2014 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.
+ */
+
     .syntax unified
-    .cpu cortex-m4
+    .cpu cortex-m3
     .thumb
-    .text
+
+    .section .text
     .align  2
 
-@ uint gc_helper_get_regs_and_sp(r0=uint regs[10])
     .global gc_helper_get_regs_and_sp
-    .thumb
-    .thumb_func
-    .type   gc_helper_get_regs_and_sp, %function
+    .type gc_helper_get_regs_and_sp, %function
+
+@ uint gc_helper_get_regs_and_sp(r0=uint regs[10])
 gc_helper_get_regs_and_sp:
     @ store registers into given array
     str     r4, [r0], #4
@@ -26,37 +52,4 @@ gc_helper_get_regs_and_sp:
     mov     r0, sp
     bx      lr
 
-
-@ this next function is now obsolete
-
-    .size   gc_helper_get_regs_and_clean_stack, .-gc_helper_get_regs_and_clean_stack
-@ void gc_helper_get_regs_and_clean_stack(r0=uint regs[10], r1=heap_end)
-    .global gc_helper_get_regs_and_clean_stack
-    .thumb
-    .thumb_func
-    .type   gc_helper_get_regs_and_clean_stack, %function
-gc_helper_get_regs_and_clean_stack:
-    @ store registers into given array
-    str     r4, [r0], #4
-    str     r5, [r0], #4
-    str     r6, [r0], #4
-    str     r7, [r0], #4
-    str     r8, [r0], #4
-    str     r9, [r0], #4
-    str     r10, [r0], #4
-    str     r11, [r0], #4
-    str     r12, [r0], #4
-    str     r13, [r0], #4
-
-    @ clean the stack from given pointer up to current sp
-    movs    r0, #0
-    mov     r2, sp
-    b.n     .entry
-.loop:
-    str     r0, [r1], #4
-.entry:
-    cmp     r1, r2
-    bcc.n   .loop
-    bx      lr
-
-    .size   gc_helper_get_regs_and_clean_stack, .-gc_helper_get_regs_and_clean_stack
+    .size gc_helper_get_regs_and_sp, .-gc_helper_get_regs_and_sp