[LLVMdev] Autovectorization questions

[Chandler Carruth]

On Wed, Mar 12, 2014 at 3:50 PM, Arnold Schwaighofer <
aschwaighofer at apple.com> wrote:

> In order to vectorize code like this LLVM needs to prove that “A[i*7]”
> does not wrap in the address space. It fails to do so


But, why?

I'm moderately sure that neither C nor C++ allow wrapping around the end of
the address space. If they do, we will fix C++ at least to disallow this.
'i' is a signed integer, so we can't wrap in the index space either. So why
can't LLVM prove this?
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