[Bug target/50106] [ARM] Wrong code with -march=armv5t -mthumb -Os

["sebastian dot huber at embedded-brains dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50106

--- Comment #11 from Sebastian Huber <sebastian.huber@embedded-brains.de> 2011-10-20 11:07:09 UTC ---
Thank you very much.  With this change the GCC 4.6.2-RC-20111019 produces now
correct code in this case.

I know understand why the unused volatile registers are saved and restored. 
This is to get rid of the arithmetic stack adjustments.

--- test.Os.GCC-4.5.s   2011-10-20 13:04:15.384638860 +0200
+++ test.Os.GCC-4.6.s   2011-10-20 13:04:15.396639237 +0200
@@ -17,32 +17,29 @@
        .thumb_func
        .type   _GetIDS, %function
 _GetIDS:
-       push    {lr}
-       ldr     r2, .L4
-       sub     sp, sp, #12
-       ldr     r2, [r2]
-       mov     r3, r0
+       push    {r0, r1, r2, lr}
+       ldr     r3, .L4
        ldr     r1, .L4+4
-       add     r0, sp, #4
-       cmp     r3, r2
+       ldr     r3, [r3]
+       cmp     r0, r3
        bge     .L2
-       lsl     r3, r3, #1
-       add     r1, r1, r3
+       lsl     r0, r0, #1
+       add     r1, r1, r0
 .L2:
        mov     r2, #2
+       add     r0, sp, #4
        bl      memcpy
        add     r3, sp, #4
        ldrb    r0, [r3, #1]
        ldrb    r2, [r3]
        lsl     r0, r0, #8
-       add     sp, sp, #12
-       orr     r0, r0, r2
+       orr     r0, r2
        @ sp needed for prologue
-       pop     {pc}
+       pop     {r1, r2, r3, pc}
 .L5:
        .align  2
 .L4:
        .word   _LIST_SIZE
        .word   _List
        .size   _GetIDS, .-_GetIDS
-       .ident  "GCC: (GNU) 4.5.4 20111013 (prerelease)"
+       .ident  "GCC: (GNU) 4.6.2 20111019 (prerelease)"