[Bug rtl-optimization/45813] alias analysis problem ?

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45813

--- Comment #10 from Mikael Pettersson <mikpe at it dot uu.se> 2010-09-29 20:59:17 UTC ---
This was fixed for 4.6 by r160260:
http://gcc.gnu.org/viewcvs?view=revision&revision=160260

Applying that to 4.5 changes 4.5's output to:

ReadLE16U:
        push    {r7, lr}
        ldrb    r3, [r0]
        sub     sp, sp, #8
        add     r7, sp, #0
        strb    r3, [r7, #6]
        ldrb    r3, [r0, #1]
        mov     sp, r7
        add     sp, sp, #8
        strb    r3, [r7, #7]
        ldrh    r0, [r7, #6]
        @ sp needed for prologue
        pop     {r7, pc}

which is much better.  (It still runs into PR38644, but that can be avoided by
-fno-schedule-insns2 or by applying my proposed patch for PR38644.)