[PATCH] D27560: Always run GlobalDCE at O0

[Duncan P. N. Exon Smith via llvm-commits]

I agree that ideally we would teach Clang not to emit the code, but last I checked -O0 has a number of IR-modifying passes thanks to the sanitizers.  To understand how the frontend is (mis)behaving, I think you already need -mllvm -disable-llvm-passes.

> On 2016-Dec-13, at 17:25, Chandler Carruth via Phabricator <reviews at reviews.llvm.org> wrote:
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> chandlerc added a comment.
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> Personally, I would much rather teach Clang to not emit code than run a pass at O0. I really would like to preserve the ability to use O0 to understand why LLVM is misbehaving.
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> (The fact that we need to run the always inliner at O0 is already somewhat frustrating, I think it makes sense to resist worsening that situation.)
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> 
> https://reviews.llvm.org/D27560
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>