On 18 September 2012 07:04, Michael Hope <michael.h...@linaro.org> wrote:
> On 17 September 2012 19:49, Zhenqiang Chen <zhenqiang.c...@linaro.org> wrote:
>> Summary
>> * Workaround the unwind issue for shrink-wrap
>> * Verify Linaro tickets.
>>
>> Details:
>> 1. Debugging the failed cases for shrink-wrap. To workaround the
>> unwind issue, update arm_expand_epilogue to generate return not
>> simple_return when sp is changed.
>
> Hmm. An interesting case for shrinkwrap is:
>
> int foo(void *p) {
> char big-on-stack-object[543234];
>
> if (p == NULL) return -1;
>
> lots-of-code-that-causes-spills-and calls()
> }
>
> as shortcutting the prologue is where we get the saving. Does the
> prologue normally touch SP, or is this for alloca() style functions
> only?
For spilling and alloca() style functions, prologue will touch SP.
For a local array, prologue will also touch SP if accessing the array
element. My logs show, gcc will generate code like
sub sp, sp, #size of the array
...
ldr r3, [sp, offset]
Thanks!
-Zhenqiang
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