Merging r326394:

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r326394 | rnk | 2018-02-28 16:09:35 -0800 (Wed, 28 Feb 2018) | 10 lines

[DAE] don't remove args of musttail target/caller

`musttail` requires identical signatures of caller and callee. Removing
arguments breaks `musttail` semantics.

PR36441

Patch by Fedor Indutny

Differential Revision: https://reviews.llvm.org/D43708
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llvm-svn: 334464