source: trunk/libs/newlib/src/libgloss/m32r/crt0.S @ 546

Last change on this file since 546 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 1.2 KB
Line 
1        .text
2        .balign 4
3        .global _start
4_start:
5
6        seth    sp, #shigh(_stack)
7        add3    sp, sp, #low(_stack)
8        ldi     fp, #0
9
10# Clear the BSS.  Do it in two parts for efficiency: longwords first
11# for most of it, then the remaining 0 to 3 bytes.
12
13        seth    r2, #shigh(__bss_start)
14        add3    r2, r2, #low(__bss_start); R2 = start of BSS
15        seth    r3, #shigh(_end)
16        add3    r3, r3, #low(_end)      ; R3 = end of BSS + 1
17       
18        sub     r3, r2          ; R3 = BSS size in bytes
19        mv      r4, r3
20        srli    r4, #2          ; R4 = BSS size in longwords (rounded down)
21        ldi     r1, #0          ; clear R1 for longword store
22        addi    r2, #-4         ; account for pre-inc store
23        beqz    r4, .Lendloop1  ; any more to go?
24.Lloop1:
25        st      r1, @+r2        ; yep, zero out another longword
26        addi    r4, #-1         ; decrement count
27        bnez    r4, .Lloop1     ; go do some more
28.Lendloop1:
29        and3    r4, r3, #3      ; get no. of remaining BSS bytes to clear
30        addi    r2, #4          ; account for pre-inc store
31        beqz    r4, .Lendloop2  ; any more to go?
32.Lloop2:
33        stb     r1, @r2         ; yep, zero out another byte
34        addi    r2, #1          ; bump address
35        addi    r4, #-1         ; decrement count
36        bnez    r4, .Lloop2     ; go do some more
37.Lendloop2:
38
39# Run code in the .init section.
40# This will queue the .fini section to be run with atexit.
41
42        bl      __init
43
44# Call main, then exit.
45
46        bl      main
47        bl      exit
48
49# If that fails just loop.
50
51.Lexit:
52        bra     .Lexit
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