[CodeGen] Merge equivalent block copy/helper functions.

Clang generates copy and dispose helper functions for each block literal
on the stack. Often these functions are equivalent for different blocks.
This commit makes changes to merge equivalent copy and dispose helper
functions and reduce code size.

To enable merging equivalent copy/dispose functions, the captured object
infomation is encoded into the helper function name. This allows IRGen
to check whether an equivalent helper function has already been emitted
and reuse the function instead of generating a new helper function
whenever a block is defined. In addition, the helper functions are
marked as linkonce_odr to enable merging helper functions that have the
same name across translation units and marked as unnamed_addr to enable
the linker's deduplication pass to merge functions that have different
names but the same content.

rdar://problem/42640608

Differential Revision: https://reviews.llvm.org/D50152

llvm-svn: 339438

1 files changed, 198 insertions, 56 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 5d03477e9bd..b1dbb505b5d 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "CGBlocks.h"
+#include "CGCXXABI.h"
 #include "CGDebugInfo.h"
 #include "CGObjCRuntime.h"
 #include "CGOpenCLRuntime.h"
@@ -25,6 +26,7 @@
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Support/ScopedPrinter.h"
 #include <algorithm>
 #include <cstdio>
 
@@ -34,8 +36,8 @@ using namespace CodeGen;
 CGBlockInfo::CGBlockInfo(const BlockDecl *block, StringRef name)
   : Name(name), CXXThisIndex(0), CanBeGlobal(false), NeedsCopyDispose(false),
     HasCXXObject(false), UsesStret(false), HasCapturedVariableLayout(false),
-    LocalAddress(Address::invalid()), StructureType(nullptr), Block(block),
-    DominatingIP(nullptr) {
+    CapturesNonExternalType(false), LocalAddress(Address::invalid()),
+    StructureType(nullptr), Block(block), DominatingIP(nullptr) {
 
   // Skip asm prefix, if any.  'name' is usually taken directly from
   // the mangled name of the enclosing function.
@@ -464,6 +466,8 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
     } else if (CI.hasCopyExpr()) {
       info.NeedsCopyDispose = true;
       info.HasCXXObject = true;
+      if (!variable->getType()->getAsCXXRecordDecl()->isExternallyVisible())
+        info.CapturesNonExternalType = true;
 
     // So do C structs that require non-trivial copy construction or
     // destruction.
@@ -480,6 +484,8 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
         if (!record->hasTrivialDestructor()) {
           info.HasCXXObject = true;
           info.NeedsCopyDispose = true;
+          if (!record->isExternallyVisible())
+            info.CapturesNonExternalType = true;
         }
       }
     }
@@ -1522,13 +1528,17 @@ enum class BlockCaptureEntityKind {
 struct BlockCaptureManagedEntity {
   BlockCaptureEntityKind Kind;
   BlockFieldFlags Flags;
-  const BlockDecl::Capture &CI;
-  const CGBlockInfo::Capture &Capture;
+  const BlockDecl::Capture *CI;
+  const CGBlockInfo::Capture *Capture;
 
   BlockCaptureManagedEntity(BlockCaptureEntityKind Type, BlockFieldFlags Flags,
                             const BlockDecl::Capture &CI,
                             const CGBlockInfo::Capture &Capture)
-      : Kind(Type), Flags(Flags), CI(CI), Capture(Capture) {}
+      : Kind(Type), Flags(Flags), CI(&CI), Capture(&Capture) {}
+
+  bool operator<(const BlockCaptureManagedEntity &Other) const {
+    return Capture->getOffset() < Other.Capture->getOffset();
+  }
 };
 
 } // end anonymous namespace
@@ -1607,6 +1617,9 @@ static void findBlockCapturedManagedEntities(
     if (Info.first != BlockCaptureEntityKind::None)
       ManagedCaptures.emplace_back(Info.first, Info.second, CI, Capture);
   }
+
+  // Sort the captures by offset.
+  llvm::sort(ManagedCaptures.begin(), ManagedCaptures.end());
 }
 
 namespace {
@@ -1614,10 +1627,12 @@ namespace {
 struct CallBlockRelease final : EHScopeStack::Cleanup {
   Address Addr;
   BlockFieldFlags FieldFlags;
-  bool LoadBlockVarAddr;
+  bool LoadBlockVarAddr, CanThrow;
 
-  CallBlockRelease(Address Addr, BlockFieldFlags Flags, bool LoadValue)
-      : Addr(Addr), FieldFlags(Flags), LoadBlockVarAddr(LoadValue) {}
+  CallBlockRelease(Address Addr, BlockFieldFlags Flags, bool LoadValue,
+                   bool CT)
+      : Addr(Addr), FieldFlags(Flags), LoadBlockVarAddr(LoadValue),
+        CanThrow(CT) {}
 
   void Emit(CodeGenFunction &CGF, Flags flags) override {
     llvm::Value *BlockVarAddr;
@@ -1628,15 +1643,112 @@ struct CallBlockRelease final : EHScopeStack::Cleanup {
       BlockVarAddr = Addr.getPointer();
     }
 
-    CGF.BuildBlockRelease(BlockVarAddr, FieldFlags);
+    CGF.BuildBlockRelease(BlockVarAddr, FieldFlags, CanThrow);
   }
 };
 } // end anonymous namespace
 
+/// Check if \p T is a C++ class that has a destructor that can throw.
+bool CodeGenFunction::cxxDestructorCanThrow(QualType T) {
+  if (const auto *RD = T->getAsCXXRecordDecl())
+    if (const CXXDestructorDecl *DD = RD->getDestructor())
+      return DD->getType()->getAs<FunctionProtoType>()->canThrow();
+  return false;
+}
+
+static std::string getCopyDestroyHelperFuncName(
+    const SmallVectorImpl<BlockCaptureManagedEntity> &Captures,
+    CharUnits BlockAlignment, bool IsCopyHelper, CodeGenModule &CGM) {
+  ASTContext &Ctx = CGM.getContext();
+  std::unique_ptr<ItaniumMangleContext> MC(
+      ItaniumMangleContext::create(Ctx, Ctx.getDiagnostics()));
+
+  std::string Name =
+      IsCopyHelper ? "__copy_helper_block_" : "__destroy_helper_block_";
+  if (CGM.getLangOpts().Exceptions)
+    Name += "e";
+  if (CGM.getCodeGenOpts().ObjCAutoRefCountExceptions)
+    Name += "a";
+  Name += llvm::to_string(BlockAlignment.getQuantity()) + "_";
+
+  for (const BlockCaptureManagedEntity &E : Captures) {
+    const BlockDecl::Capture &CI = *E.CI;
+    BlockFieldFlags Flags = E.Flags;
+    QualType CaptureTy = CI.getVariable()->getType();
+    Name += llvm::to_string(E.Capture->getOffset().getQuantity());
+
+    switch (E.Kind) {
+    case BlockCaptureEntityKind::CXXRecord: {
+      Name += "c";
+      SmallString<256> Str;
+      llvm::raw_svector_ostream Out(Str);
+      MC->mangleTypeName(CaptureTy, Out);
+      Name += llvm::to_string(Str.size()) + Str.c_str();
+      break;
+    }
+    case BlockCaptureEntityKind::ARCWeak:
+      Name += "w";
+      break;
+    case BlockCaptureEntityKind::ARCStrong:
+      Name += "s";
+      break;
+    case BlockCaptureEntityKind::BlockObject: {
+      const VarDecl *Var = CI.getVariable();
+      unsigned F = Flags.getBitMask();
+      if (F & BLOCK_FIELD_IS_BYREF) {
+        Name += "r";
+        if (F & BLOCK_FIELD_IS_WEAK)
+          Name += "w";
+        else {
+          if (IsCopyHelper) {
+            if (Ctx.getBlockVarCopyInit(Var).canThrow())
+              Name += "c";
+          } else {
+            if (CodeGenFunction::cxxDestructorCanThrow(CaptureTy))
+              Name += "d";
+          }
+        }
+      } else {
+        assert((F & BLOCK_FIELD_IS_OBJECT) && "unexpected flag value");
+        if (F == BLOCK_FIELD_IS_BLOCK)
+          Name += "b";
+        else
+          Name += "o";
+      }
+      break;
+    }
+    case BlockCaptureEntityKind::NonTrivialCStruct: {
+      bool IsVolatile = CaptureTy.isVolatileQualified();
+      CharUnits Alignment =
+          BlockAlignment.alignmentAtOffset(E.Capture->getOffset());
+
+      Name += "n";
+      std::string Str;
+      if (IsCopyHelper)
+        Str = CodeGenFunction::getNonTrivialCopyConstructorStr(
+            CaptureTy, Alignment, IsVolatile, Ctx);
+      else
+        Str = CodeGenFunction::getNonTrivialDestructorStr(CaptureTy, Alignment,
+                                                          IsVolatile, Ctx);
+      // The underscore is necessary here because non-trivial copy constructor
+      // and destructor strings can start with a number.
+      Name += llvm::to_string(Str.size()) + "_" + Str;
+      break;
+    }
+    case BlockCaptureEntityKind::None:
+      llvm_unreachable("unexpected block capture kind");
+    }
+  }
+
+  return Name;
+}
+
 static void pushCaptureCleanup(BlockCaptureEntityKind CaptureKind,
                                Address Field, QualType CaptureType,
-                               BlockFieldFlags Flags, bool EHOnly,
-                               CodeGenFunction &CGF) {
+                               BlockFieldFlags Flags, bool ForCopyHelper,
+                               VarDecl *Var, CodeGenFunction &CGF) {
+  bool EHOnly = ForCopyHelper;
+
   switch (CaptureKind) {
   case BlockCaptureEntityKind::CXXRecord:
   case BlockCaptureEntityKind::ARCWeak:
@@ -1658,7 +1770,13 @@ static void pushCaptureCleanup(BlockCaptureEntityKind CaptureKind,
   case BlockCaptureEntityKind::BlockObject: {
     if (!EHOnly || CGF.getLangOpts().Exceptions) {
       CleanupKind Kind = EHOnly ? EHCleanup : NormalAndEHCleanup;
-      CGF.enterByrefCleanup(Kind, Field, Flags, /*LoadBlockVarAddr*/ true);
+      // Calls to _Block_object_dispose along the EH path in the copy helper
+      // function don't throw as newly-copied __block variables always have a
+      // reference count of 2.
+      bool CanThrow =
+          !ForCopyHelper && CGF.cxxDestructorCanThrow(CaptureType);
+      CGF.enterByrefCleanup(Kind, Field, Flags, /*LoadBlockVarAddr*/ true,
+                            CanThrow);
     }
     break;
   }
@@ -1667,6 +1785,19 @@ static void pushCaptureCleanup(BlockCaptureEntityKind CaptureKind,
   }
 }
 
+static void setBlockHelperAttributesVisibility(bool CapturesNonExternalType,
+                                               llvm::Function *Fn,
+                                               const CGFunctionInfo &FI,
+                                               CodeGenModule &CGM) {
+  if (CapturesNonExternalType) {
+    CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, FI);
+  } else {
+    Fn->setVisibility(llvm::GlobalValue::HiddenVisibility);
+    Fn->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+    CGM.SetLLVMFunctionAttributes(nullptr, FI, Fn);
+    CGM.SetLLVMFunctionAttributesForDefinition(nullptr, Fn);
+  }
+}
 /// Generate the copy-helper function for a block closure object:
 ///   static void block_copy_helper(block_t *dst, block_t *src);
 /// The runtime will have previously initialized 'dst' by doing a
@@ -1677,6 +1808,16 @@ static void pushCaptureCleanup(BlockCaptureEntityKind CaptureKind,
 /// the contents of an individual __block variable to the heap.
 llvm::Constant *
 CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
+  SmallVector<BlockCaptureManagedEntity, 4> CopiedCaptures;
+  findBlockCapturedManagedEntities(blockInfo, getLangOpts(), CopiedCaptures,
+                                   computeCopyInfoForBlockCapture);
+  std::string FuncName =
+      getCopyDestroyHelperFuncName(CopiedCaptures, blockInfo.BlockAlign,
+                                   /*IsCopyHelper*/ true, CGM);
+
+  if (llvm::GlobalValue *Func = CGM.getModule().getNamedValue(FuncName))
+    return Func;
+
   ASTContext &C = getContext();
 
   FunctionArgList args;
@@ -1695,11 +1836,11 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
   llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
 
   llvm::Function *Fn =
-    llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
-                           "__copy_helper_block_", &CGM.getModule());
+    llvm::Function::Create(LTy, llvm::GlobalValue::LinkOnceODRLinkage,
+                           FuncName, &CGM.getModule());
 
   IdentifierInfo *II
-    = &CGM.getContext().Idents.get("__copy_helper_block_");
+    = &CGM.getContext().Idents.get(FuncName);
 
   FunctionDecl *FD = FunctionDecl::Create(C,
                                           C.getTranslationUnitDecl(),
@@ -1709,8 +1850,8 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
                                           false,
                                           false);
 
-  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, FI);
-
+  setBlockHelperAttributesVisibility(blockInfo.CapturesNonExternalType, Fn, FI,
+                                     CGM);
   StartFunction(FD, C.VoidTy, Fn, FI, args);
   ApplyDebugLocation NL{*this, blockInfo.getBlockExpr()->getBeginLoc()};
   llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
@@ -1723,13 +1864,9 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
   dst = Address(Builder.CreateLoad(dst), blockInfo.BlockAlign);
   dst = Builder.CreateBitCast(dst, structPtrTy, "block.dest");
 
-  SmallVector<BlockCaptureManagedEntity, 4> CopiedCaptures;
-  findBlockCapturedManagedEntities(blockInfo, getLangOpts(), CopiedCaptures,
-                                   computeCopyInfoForBlockCapture);
-
   for (const auto &CopiedCapture : CopiedCaptures) {
-    const BlockDecl::Capture &CI = CopiedCapture.CI;
-    const CGBlockInfo::Capture &capture = CopiedCapture.Capture;
+    const BlockDecl::Capture &CI = *CopiedCapture.CI;
+    const CGBlockInfo::Capture &capture = *CopiedCapture.Capture;
     QualType captureType = CI.getVariable()->getType();
     BlockFieldFlags flags = CopiedCapture.Flags;
 
@@ -1783,28 +1920,17 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
           dstAddr, srcValue, llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
         };
 
-        const VarDecl *variable = CI.getVariable();
-        bool copyCanThrow = false;
-        if (CI.isByRef() && variable->getType()->getAsCXXRecordDecl()) {
-          const Expr *copyExpr =
-            CGM.getContext().getBlockVarCopyInits(variable);
-          if (copyExpr) {
-            copyCanThrow = true; // FIXME: reuse the noexcept logic
-          }
-        }
-
-        if (copyCanThrow) {
+        if (CI.isByRef() && C.getBlockVarCopyInit(CI.getVariable()).canThrow())
           EmitRuntimeCallOrInvoke(CGM.getBlockObjectAssign(), args);
-        } else {
+        else
           EmitNounwindRuntimeCall(CGM.getBlockObjectAssign(), args);
-        }
       }
     }
 
     // Ensure that we destroy the copied object if an exception is thrown later
     // in the helper function.
-    pushCaptureCleanup(CopiedCapture.Kind, dstField, captureType, flags, /*EHOnly*/ true,
-                       *this);
+    pushCaptureCleanup(CopiedCapture.Kind, dstField, captureType, flags,
+                       /*ForCopyHelper*/ true, CI.getVariable(), *this);
   }
 
   FinishFunction();
@@ -1868,6 +1994,16 @@ computeDestroyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
 /// variable.
 llvm::Constant *
 CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
+  SmallVector<BlockCaptureManagedEntity, 4> DestroyedCaptures;
+  findBlockCapturedManagedEntities(blockInfo, getLangOpts(), DestroyedCaptures,
+                                   computeDestroyInfoForBlockCapture);
+  std::string FuncName =
+      getCopyDestroyHelperFuncName(DestroyedCaptures, blockInfo.BlockAlign,
+                                   /*IsCopyHelper*/ false, CGM);
+
+  if (llvm::GlobalValue *Func = CGM.getModule().getNamedValue(FuncName))
+    return Func;
+
   ASTContext &C = getContext();
 
   FunctionArgList args;
@@ -1883,11 +2019,11 @@ CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
   llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
 
   llvm::Function *Fn =
-    llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
-                           "__destroy_helper_block_", &CGM.getModule());
+    llvm::Function::Create(LTy, llvm::GlobalValue::LinkOnceODRLinkage,
+                           FuncName, &CGM.getModule());
 
   IdentifierInfo *II
-    = &CGM.getContext().Idents.get("__destroy_helper_block_");
+    = &CGM.getContext().Idents.get(FuncName);
 
   FunctionDecl *FD = FunctionDecl::Create(C, C.getTranslationUnitDecl(),
                                           SourceLocation(),
@@ -1895,9 +2031,11 @@ CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
                                           nullptr, SC_Static,
                                           false, false);
 
-  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, FI);
-
+  setBlockHelperAttributesVisibility(blockInfo.CapturesNonExternalType, Fn, FI,
+                                     CGM);
   StartFunction(FD, C.VoidTy, Fn, FI, args);
+  markAsIgnoreThreadCheckingAtRuntime(Fn);
+
   ApplyDebugLocation NL{*this, blockInfo.getBlockExpr()->getBeginLoc()};
 
   llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
@@ -1908,20 +2046,17 @@ CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
 
   CodeGenFunction::RunCleanupsScope cleanups(*this);
 
-  SmallVector<BlockCaptureManagedEntity, 4> DestroyedCaptures;
-  findBlockCapturedManagedEntities(blockInfo, getLangOpts(), DestroyedCaptures,
-                                   computeDestroyInfoForBlockCapture);
-
   for (const auto &DestroyedCapture : DestroyedCaptures) {
-    const BlockDecl::Capture &CI = DestroyedCapture.CI;
-    const CGBlockInfo::Capture &capture = DestroyedCapture.Capture;
+    const BlockDecl::Capture &CI = *DestroyedCapture.CI;
+    const CGBlockInfo::Capture &capture = *DestroyedCapture.Capture;
     BlockFieldFlags flags = DestroyedCapture.Flags;
 
     Address srcField =
       Builder.CreateStructGEP(src, capture.getIndex(), capture.getOffset());
 
     pushCaptureCleanup(DestroyedCapture.Kind, srcField,
-                       CI.getVariable()->getType(), flags, /*EHOnly*/ false, *this);
+                       CI.getVariable()->getType(), flags,
+                       /*ForCopyHelper*/ false, CI.getVariable(), *this);
   }
 
   cleanups.ForceCleanup();
@@ -1961,7 +2096,7 @@ public:
     field = CGF.Builder.CreateBitCast(field, CGF.Int8PtrTy->getPointerTo(0));
     llvm::Value *value = CGF.Builder.CreateLoad(field);
 
-    CGF.BuildBlockRelease(value, Flags | BLOCK_BYREF_CALLER);
+    CGF.BuildBlockRelease(value, Flags | BLOCK_BYREF_CALLER, false);
   }
 
   void profileImpl(llvm::FoldingSetNodeID &id) const override {
@@ -2288,7 +2423,8 @@ CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
     byrefInfo.ByrefAlignment.alignmentAtOffset(byrefInfo.FieldOffset);
 
   if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
-    const Expr *copyExpr = CGM.getContext().getBlockVarCopyInits(&var);
+    const Expr *copyExpr =
+        CGM.getContext().getBlockVarCopyInit(&var).getCopyExpr();
     if (!copyExpr && record->hasTrivialDestructor()) return nullptr;
 
     return ::buildByrefHelpers(
@@ -2591,19 +2727,25 @@ void CodeGenFunction::emitByrefStructureInit(const AutoVarEmission &emission) {
   }
 }
 
-void CodeGenFunction::BuildBlockRelease(llvm::Value *V, BlockFieldFlags flags) {
+void CodeGenFunction::BuildBlockRelease(llvm::Value *V, BlockFieldFlags flags,
+                                        bool CanThrow) {
   llvm::Value *F = CGM.getBlockObjectDispose();
   llvm::Value *args[] = {
     Builder.CreateBitCast(V, Int8PtrTy),
     llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
   };
-  EmitNounwindRuntimeCall(F, args); // FIXME: throwing destructors?
+
+  if (CanThrow)
+    EmitRuntimeCallOrInvoke(F, args);
+  else
+    EmitNounwindRuntimeCall(F, args);
 }
 
 void CodeGenFunction::enterByrefCleanup(CleanupKind Kind, Address Addr,
                                         BlockFieldFlags Flags,
-                                        bool LoadBlockVarAddr) {
-  EHStack.pushCleanup<CallBlockRelease>(Kind, Addr, Flags, LoadBlockVarAddr);
+                                        bool LoadBlockVarAddr, bool CanThrow) {
+  EHStack.pushCleanup<CallBlockRelease>(Kind, Addr, Flags, LoadBlockVarAddr,
+                                        CanThrow);
 }
 
 /// Adjust the declaration of something from the blocks API.