Remove threshold for lifetime marker insertion of named temporaries

Now that TailRecursionElimination has been fixed with r222354, the
threshold on size for lifetime marker insertion can be removed. This
only affects named temporary though, as the patch for unnamed temporaries
is still in progress.

llvm-svn: 222993

2 files changed, 29 insertions, 26 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 959ac9a8d7e..48ba97d2ae2 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -512,10 +512,7 @@ namespace {
       : Addr(addr), Size(size) {}
 
     void Emit(CodeGenFunction &CGF, Flags flags) override {
-      llvm::Value *castAddr = CGF.Builder.CreateBitCast(Addr, CGF.Int8PtrTy);
-      CGF.Builder.CreateCall2(CGF.CGM.getLLVMLifetimeEndFn(),
-                              Size, castAddr)
-        ->setDoesNotThrow();
+      CGF.EmitLifetimeEnd(Size, Addr);
     }
   };
 }
@@ -835,21 +832,6 @@ static bool shouldUseMemSetPlusStoresToInitialize(llvm::Constant *Init,
          canEmitInitWithFewStoresAfterMemset(Init, StoreBudget);
 }
 
-/// Should we use the LLVM lifetime intrinsics for the given local variable?
-static bool shouldUseLifetimeMarkers(CodeGenFunction &CGF, const VarDecl &D,
-                                     unsigned Size) {
-  // For now, only in optimized builds.
-  if (CGF.CGM.getCodeGenOpts().OptimizationLevel == 0)
-    return false;
-
-  // Limit the size of marked objects to 32 bytes. We don't want to increase
-  // compile time by marking tiny objects.
-  unsigned SizeThreshold = 32;
-
-  return Size > SizeThreshold;
-}
-
-
 /// EmitAutoVarDecl - Emit code and set up an entry in LocalDeclMap for a
 /// variable declaration with auto, register, or no storage class specifier.
 /// These turn into simple stack objects, or GlobalValues depending on target.
@@ -859,6 +841,29 @@ void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D) {
   EmitAutoVarCleanups(emission);
 }
 
+/// Emit a lifetime.begin marker if some criteria are satisfied.
+/// \return a pointer to the temporary size Value if a marker was emitted, null
+/// otherwise
+llvm::Value *CodeGenFunction::EmitLifetimeStart(uint64_t Size,
+                                                llvm::Value *Addr) {
+  // For now, only in optimized builds.
+  if (CGM.getCodeGenOpts().OptimizationLevel == 0)
+    return nullptr;
+
+  llvm::Value *SizeV = llvm::ConstantInt::get(Int64Ty, Size);
+  llvm::Value *CastAddr = Builder.CreateBitCast(Addr, Int8PtrTy);
+  Builder.CreateCall2(CGM.getLLVMLifetimeStartFn(), SizeV, CastAddr)
+      ->setDoesNotThrow();
+
+  return SizeV;
+}
+
+void CodeGenFunction::EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr) {
+  llvm::Value *CastAddr = Builder.CreateBitCast(Addr, Int8PtrTy);
+  Builder.CreateCall2(CGM.getLLVMLifetimeEndFn(), Size, CastAddr)
+      ->setDoesNotThrow();
+}
+
 /// EmitAutoVarAlloca - Emit the alloca and debug information for a
 /// local variable.  Does not emit initialization or destruction.
 CodeGenFunction::AutoVarEmission
@@ -954,13 +959,8 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
       // Emit a lifetime intrinsic if meaningful.  There's no point
       // in doing this if we don't have a valid insertion point (?).
       uint64_t size = CGM.getDataLayout().getTypeAllocSize(LTy);
-      if (HaveInsertPoint() && shouldUseLifetimeMarkers(*this, D, size)) {
-        llvm::Value *sizeV = llvm::ConstantInt::get(Int64Ty, size);
-
-        emission.SizeForLifetimeMarkers = sizeV;
-        llvm::Value *castAddr = Builder.CreateBitCast(Alloc, Int8PtrTy);
-        Builder.CreateCall2(CGM.getLLVMLifetimeStartFn(), sizeV, castAddr)
-          ->setDoesNotThrow();
+      if (HaveInsertPoint()) {
+        emission.SizeForLifetimeMarkers = EmitLifetimeStart(size, Alloc);
       } else {
         assert(!emission.useLifetimeMarkers());
       }
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 4575e31dbd2..198cf504903 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -1743,6 +1743,9 @@ public:
   void EmitCXXTemporary(const CXXTemporary *Temporary, QualType TempType,
                         llvm::Value *Ptr);
 
+  llvm::Value *EmitLifetimeStart(uint64_t Size, llvm::Value *Addr);
+  void EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr);
+
   llvm::Value *EmitCXXNewExpr(const CXXNewExpr *E);
   void EmitCXXDeleteExpr(const CXXDeleteExpr *E);