http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50106
--- Comment #11 from Sebastian Huber <sebastian.hu...@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)"