[NFC] CGDecl factor out constant emission

The code is cleaner this way, and with some changes I'm playing with it makes sense to split it out so we can reuse it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@339191 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGDecl.cpp

@@ -1055,6 +1055,61 @@ static BytePattern shouldUseMemSetToInitialize(llvm::Constant *Init,
   return constantIsRepeatedBytePattern(Init);
 }
 
+static void emitStoresForConstant(CodeGenModule &CGM, const VarDecl &D,
+                                  Address Loc, bool isVolatile,
+                                  CGBuilderTy &Builder,
+                                  llvm::Constant *constant) {
+  auto *Int8Ty = llvm::IntegerType::getInt8Ty(CGM.getLLVMContext());
+  auto *IntPtrTy = CGM.getDataLayout().getIntPtrType(CGM.getLLVMContext());
+
+  // If the initializer is all or mostly the same, codegen with bzero / memset
+  // then do a few stores afterward.
+  uint64_t ConstantSize =
+      CGM.getDataLayout().getTypeAllocSize(constant->getType());
+  auto *SizeVal = llvm::ConstantInt::get(IntPtrTy, ConstantSize);
+  if (shouldUseBZeroPlusStoresToInitialize(constant, ConstantSize)) {
+    Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal,
+                         isVolatile);
+
+    bool valueAlreadyCorrect =
+        constant->isNullValue() || isa<llvm::UndefValue>(constant);
+    if (!valueAlreadyCorrect) {
+      Loc = Builder.CreateBitCast(
+          Loc, constant->getType()->getPointerTo(Loc.getAddressSpace()));
+      emitStoresForInitAfterBZero(CGM, constant, Loc, isVolatile, Builder);
+    }
+    return;
+  }
+
+  BytePattern Pattern = shouldUseMemSetToInitialize(constant, ConstantSize);
+  if (!Pattern.isNone()) {
+    uint8_t Value = Pattern.isAny() ? 0x00 : Pattern.getValue();
+    Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, Value), SizeVal,
+                         isVolatile);
+    return;
+  }
+
+  // Otherwise, create a temporary global with the initializer then memcpy from
+  // the global to the alloca.
+  std::string Name = getStaticDeclName(CGM, D);
+  unsigned AS = CGM.getContext().getTargetAddressSpace(
+      CGM.getStringLiteralAddressSpace());
+  llvm::Type *BP = llvm::PointerType::getInt8PtrTy(CGM.getLLVMContext(), AS);
+
+  llvm::GlobalVariable *GV = new llvm::GlobalVariable(
+      CGM.getModule(), constant->getType(), true,
+      llvm::GlobalValue::PrivateLinkage, constant, Name, nullptr,
+      llvm::GlobalValue::NotThreadLocal, AS);
+  GV->setAlignment(Loc.getAlignment().getQuantity());
+  GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+
+  Address SrcPtr = Address(GV, Loc.getAlignment());
+  if (SrcPtr.getType() != BP)
+    SrcPtr = Builder.CreateBitCast(SrcPtr, BP);
+
+  Builder.CreateMemCpy(Loc, SrcPtr, SizeVal, isVolatile);
+}
+
 /// 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.
@@ -1500,57 +1555,11 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) {
   // in various ways.
   bool isVolatile = type.isVolatileQualified();
 
-  llvm::Value *SizeVal =
-    llvm::ConstantInt::get(IntPtrTy,
-                           getContext().getTypeSizeInChars(type).getQuantity());
-
   llvm::Type *BP = CGM.Int8Ty->getPointerTo(Loc.getAddressSpace());
   if (Loc.getType() != BP)
     Loc = Builder.CreateBitCast(Loc, BP);
 
-  // If the initializer is all or mostly the same, codegen with bzero / memset
-  // then do a few stores afterward.
-  uint64_t ConstantSize =
-      CGM.getDataLayout().getTypeAllocSize(constant->getType());
-  if (shouldUseBZeroPlusStoresToInitialize(constant, ConstantSize)) {
-    Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal,
-                         isVolatile);
-    // Zero and undef don't require a stores.
-    if (!constant->isNullValue() && !isa<llvm::UndefValue>(constant)) {
-      Loc = Builder.CreateBitCast(Loc,
-        constant->getType()->getPointerTo(Loc.getAddressSpace()));
-      emitStoresForInitAfterBZero(CGM, constant, Loc, isVolatile, Builder);
-    }
-    return;
-  }
-
-  BytePattern Pattern = shouldUseMemSetToInitialize(constant, ConstantSize);
-  if (!Pattern.isNone()) {
-    uint8_t Value = Pattern.isAny() ? 0x00 : Pattern.getValue();
-    Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, Value), SizeVal,
-                         isVolatile);
-    return;
-  }
-
-  // Otherwise, create a temporary global with the initializer then
-  // memcpy from the global to the alloca.
-  std::string Name = getStaticDeclName(CGM, D);
-  unsigned AS = CGM.getContext().getTargetAddressSpace(
-      CGM.getStringLiteralAddressSpace());
-  BP = llvm::PointerType::getInt8PtrTy(getLLVMContext(), AS);
-
-  llvm::GlobalVariable *GV = new llvm::GlobalVariable(
-      CGM.getModule(), constant->getType(), true,
-      llvm::GlobalValue::PrivateLinkage, constant, Name, nullptr,
-      llvm::GlobalValue::NotThreadLocal, AS);
-  GV->setAlignment(Loc.getAlignment().getQuantity());
-  GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
-
-  Address SrcPtr = Address(GV, Loc.getAlignment());
-  if (SrcPtr.getType() != BP)
-    SrcPtr = Builder.CreateBitCast(SrcPtr, BP);
-
-  Builder.CreateMemCpy(Loc, SrcPtr, SizeVal, isVolatile);
+  emitStoresForConstant(CGM, D, Loc, isVolatile, Builder, constant);
 }
 
 /// Emit an expression as an initializer for an object (variable, field, etc.)