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Re: [PATCH] mips/o32: fix internal_syscall5/6/7

On Wed, 16 Aug 2017, Maciej W. Rozycki wrote:

>  Or am I missing anything here?  E.g. is the compiler allowed to spill 
> random data to the stack at any time even in the absence of a matching 
> variable declaration?  Or is it allowed to allocate space for a non-VLA 
> variable that has been declared outside the block concerned, but the 
> lifespan of which is contained within the block in this stack space rather 
> than in the local frame?

Yes, it's allowed to do both of those.

>  If the answer to any of these questions is "yes", then would factoring 
> out the syscall `asm' along with the associated VLA declaration to a 
> helper `always_inline' function help or would it not?

I don't think that would help.  An asm can never make assumptions about 
which parts of the stack are used for what, only use its operands.

>  I mean it is a tiny optimisation, but some syscalls are frequently 
> called, so if we can avoid a waste of resources, then why not?

Are any 5/6/7-argument syscalls frequently called?

Joseph S. Myers

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