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

[Reid Kleckner]

REPOSITORY
  rL LLVM

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Comment at: lib/CodeGen/CGCall.h:158-159
@@ -157,3 +157,4 @@
   class ReturnValueSlot {
     llvm::PointerIntPair<llvm::Value *, 1, bool> Value;
+    bool IsUnused = false;
 
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There's another low alignment bit here, you should really fold it in here to keep this thing pointer-sized. You can either nest PointerIntPair<> twice or use `PointerIntPair<llvm::Value *, 2, unsigned>` Value and then do bitwise arithmetic in the helpers.

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Comment at: lib/CodeGen/CGExprAgg.cpp:65
@@ -63,4 +64,3 @@
 public:
-  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest)
-    : CGF(cgf), Builder(CGF.Builder), Dest(Dest) {
-  }
+  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest, bool isResultUnused)
+    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
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You can follow the convention for Dest and name the parameter after the member with the same case. It's correct.

http://reviews.llvm.org/D10042

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