[PATCH] Remove dead zero store to calloc initialized memory
Reid Kleckner
rnk at google.com
Thu May 29 13:55:46 PDT 2014
On Thu, May 29, 2014 at 11:53 AM, Philip Reames <listmail at philipreames.com>
wrote:
> (Again, this doesn't appear to have gone to the commits list. Anyone have
> a clue what's I'm doing wrong here?)
>
There was a behavior change when phab moved to reviews.llvm.org. Now it
doesn't send mail when you add a "subscriber" to the issue. This is
unfortunate and I'd be happy if it were fixed, but until then I try to make
sure I create the issue with llvm-commits in the subscriber field before
submitting it. Using 'arc' from the command line makes this easy, but I
know it isn't everyone's cup of tea.
> Remove dead zero store to calloc initialized memory
>
> http://reviews.llvm.org/D3942
>
> Optimize the following IR:
>
> %1 = tail call noalias i8* @calloc(i64 1, i64 4)
> %2 = bitcast i8* %1 to i32*
> ; This store is dead and should be removed
> store i32 0, i32* %2, align 4
>
> Memory returned by calloc is guaranteed to be zero initialized. If the
> value being stored is the constant zero (and the store is not otherwise
> observable across threads), we can delete the store.
>
> Note: I do not have commit rights and will need someone to commit this
> change after review.
>
> Philip
>
>
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>
>
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