[IRGen] Emit lifetime markers for temporary struct allocas
When passing arguments using temporary allocas, we need to add the
appropriate lifetime markers so that the stack coloring passes can
re-use the stack space.
This patch keeps track of all the lifetime.start calls emited before the
codegened call, and adds the corresponding lifetime.end calls after the
call.
Differential Revision: https://reviews.llvm.org/D68611
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374126
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