[PATCH] D29960: [PGO] Delay directory creation until write time

[Vedant Kumar via llvm-commits]

> On Feb 14, 2017, at 1:09 PM, Xinliang David Li <davidxl at google.com> wrote:
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> On Tue, Feb 14, 2017 at 1:04 PM, Rong Xu via Phabricator <reviews at reviews.llvm.org> wrote:
> xur added a comment.
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> why limit to merge mode?
> non-merge mode also exhibits the problem mentioned.
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> It will affect the external behavior of non-merge case -- as file truncation also needs to be delayed.

(^) This is the key point.

We can't delay file truncation, because a program with shared libraries loaded, e.g would have multiple atexit handlers which truncate/write profiles, clobbering each other.


>  Also this is relevant only for users that use profiling APIs which are mostly using merge mode.

Also true.

vedant

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> If there is a strong need to handle non-merge case, we can do this as a followup.
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> David
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> https://reviews.llvm.org/D29960
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