[PATCH] [CodeGen] Reuse stack space from unused function results (with more accurate unused result detection)

[Leny Kholodov]

Reid, first of all thank you very much for your comments. I've updated the implementation. Now I do decision about result usage inside CodeGenFunction::EmitAggExpr method. For an unused result I have incoming expression with type CallExpr. But for the used result I have two calls of EmitAggExpr method second of which has incoming expression with type MaterializeTemporaryExpr. So I decided to mark result as used in case of incoming MaterializeTemporaryExpr expression and to mark result as unused in other cases.

In the current implementation I don't use automatically cleanup mechanism for CallLifetimeEnd. I want to prepare it in separate patch.


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D10042

Files:
  lib/CodeGen/CGCall.cpp
  lib/CodeGen/CGCall.h
  lib/CodeGen/CGExprAgg.cpp
  test/CodeGenCXX/stack-reuse-miscompile.cpp
  test/CodeGenCXX/stack-reuse.cpp

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