[llvm-dev] RFC: We should stop merging allocas in the inliner

Chandler Carruth via llvm-dev llvm-dev at lists.llvm.org
Mon Aug 1 19:14:37 PDT 2016


On Mon, Aug 1, 2016 at 5:51 PM Duncan P. N. Exon Smith via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I just want to note that there's currently a miscompile in C code with
> lifetime markers:
>   http://lists.llvm.org/pipermail/cfe-dev/2016-July/050066.html
>
> Depending on how we fix that, we could end up being more pessimistic about
> when markers are emitted.  I suggest we fix that before benchmarking this
> change.
>

That shouldn't impact this change.

The inliner will emit *inlining* based lifetime markers all on its own for
any static allocas that the frontend doesn't annotate. So we could turn off
all lifetime markers in Clang and the merging here should still not be
necessary to get the stack savings.

(And I have now verified that yes, the inliner inserts these markers...)
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