1 files changed, 279 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/ConstantInitBuilder.cpp b/clang/lib/CodeGen/ConstantInitBuilder.cpp
new file mode 100644
index 000000000000..40b1607b5626
--- /dev/null
+++ b/clang/lib/CodeGen/ConstantInitBuilder.cpp
@@ -0,0 +1,279 @@
+//===--- ConstantInitBuilder.cpp - Global initializer builder -------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines out-of-line routines for building initializers for
+// global variables, in particular the kind of globals that are implicitly
+// introduced by various language ABIs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/CodeGen/ConstantInitBuilder.h"
+#include "CodeGenModule.h"
+
+using namespace clang;
+using namespace CodeGen;
+
+llvm::Type *ConstantInitFuture::getType() const {
+  assert(Data && "dereferencing null future");
+  if (Data.is<llvm::Constant*>()) {
+    return Data.get<llvm::Constant*>()->getType();
+  } else {
+    return Data.get<ConstantInitBuilderBase*>()->Buffer[0]->getType();
+  }
+}
+
+void ConstantInitFuture::abandon() {
+  assert(Data && "abandoning null future");
+  if (auto builder = Data.dyn_cast<ConstantInitBuilderBase*>()) {
+    builder->abandon(0);
+  }
+  Data = nullptr;
+}
+
+void ConstantInitFuture::installInGlobal(llvm::GlobalVariable *GV) {
+  assert(Data && "installing null future");
+  if (Data.is<llvm::Constant*>()) {
+    GV->setInitializer(Data.get<llvm::Constant*>());
+  } else {
+    auto &builder = *Data.get<ConstantInitBuilderBase*>();
+    assert(builder.Buffer.size() == 1);
+    builder.setGlobalInitializer(GV, builder.Buffer[0]);
+    builder.Buffer.clear();
+    Data = nullptr;
+  }
+}
+
+ConstantInitFuture
+ConstantInitBuilderBase::createFuture(llvm::Constant *initializer) {
+  assert(Buffer.empty() && "buffer not current empty");
+  Buffer.push_back(initializer);
+  return ConstantInitFuture(this);
+}
+
+// Only used in this file.
+inline ConstantInitFuture::ConstantInitFuture(ConstantInitBuilderBase *builder)
+    : Data(builder) {
+  assert(!builder->Frozen);
+  assert(builder->Buffer.size() == 1);
+  assert(builder->Buffer[0] != nullptr);
+}
+
+llvm::GlobalVariable *
+ConstantInitBuilderBase::createGlobal(llvm::Constant *initializer,
+                                      const llvm::Twine &name,
+                                      CharUnits alignment,
+                                      bool constant,
+                                      llvm::GlobalValue::LinkageTypes linkage,
+                                      unsigned addressSpace) {
+  auto GV = new llvm::GlobalVariable(CGM.getModule(),
+                                     initializer->getType(),
+                                     constant,
+                                     linkage,
+                                     initializer,
+                                     name,
+                                     /*insert before*/ nullptr,
+                                     llvm::GlobalValue::NotThreadLocal,
+                                     addressSpace);
+  GV->setAlignment(alignment.getQuantity());
+  resolveSelfReferences(GV);
+  return GV;
+}
+
+void ConstantInitBuilderBase::setGlobalInitializer(llvm::GlobalVariable *GV,
+                                                   llvm::Constant *initializer){
+  GV->setInitializer(initializer);
+
+  if (!SelfReferences.empty())
+    resolveSelfReferences(GV);
+}
+
+void ConstantInitBuilderBase::resolveSelfReferences(llvm::GlobalVariable *GV) {
+  for (auto &entry : SelfReferences) {
+    llvm::Constant *resolvedReference =
+      llvm::ConstantExpr::getInBoundsGetElementPtr(
+        GV->getValueType(), GV, entry.Indices);
+    auto dummy = entry.Dummy;
+    dummy->replaceAllUsesWith(resolvedReference);
+    dummy->eraseFromParent();
+  }
+  SelfReferences.clear();
+}
+
+void ConstantInitBuilderBase::abandon(size_t newEnd) {
+  // Remove all the entries we've added.
+  Buffer.erase(Buffer.begin() + newEnd, Buffer.end());
+
+  // If we're abandoning all the way to the beginning, destroy
+  // all the self-references, because we might not get another
+  // opportunity.
+  if (newEnd == 0) {
+    for (auto &entry : SelfReferences) {
+      auto dummy = entry.Dummy;
+      dummy->replaceAllUsesWith(llvm::UndefValue::get(dummy->getType()));
+      dummy->eraseFromParent();
+    }
+    SelfReferences.clear();
+  }
+}
+
+void ConstantAggregateBuilderBase::addSize(CharUnits size) {
+  add(Builder.CGM.getSize(size));
+}
+
+llvm::Constant *
+ConstantAggregateBuilderBase::getRelativeOffset(llvm::IntegerType *offsetType,
+                                                llvm::Constant *target) {
+  // Compute the address of the relative-address slot.
+  auto base = getAddrOfCurrentPosition(offsetType);
+
+  // Subtract.
+  base = llvm::ConstantExpr::getPtrToInt(base, Builder.CGM.IntPtrTy);
+  target = llvm::ConstantExpr::getPtrToInt(target, Builder.CGM.IntPtrTy);
+  llvm::Constant *offset = llvm::ConstantExpr::getSub(target, base);
+
+  // Truncate to the relative-address type if necessary.
+  if (Builder.CGM.IntPtrTy != offsetType) {
+    offset = llvm::ConstantExpr::getTrunc(offset, offsetType);
+  }
+
+  return offset;
+}
+
+llvm::Constant *
+ConstantAggregateBuilderBase::getAddrOfCurrentPosition(llvm::Type *type) {
+  // Make a global variable.  We will replace this with a GEP to this
+  // position after installing the initializer.
+  auto dummy =
+    new llvm::GlobalVariable(Builder.CGM.getModule(), type, true,
+                             llvm::GlobalVariable::PrivateLinkage,
+                             nullptr, "");
+  Builder.SelfReferences.emplace_back(dummy);
+  auto &entry = Builder.SelfReferences.back();
+  (void) getGEPIndicesToCurrentPosition(entry.Indices);
+  return dummy;
+}
+
+void ConstantAggregateBuilderBase::getGEPIndicesTo(
+                               llvm::SmallVectorImpl<llvm::Constant*> &indices,
+                               size_t position) const {
+  // Recurse on the parent builder if present.
+  if (Parent) {
+    Parent->getGEPIndicesTo(indices, Begin);
+
+  // Otherwise, add an index to drill into the first level of pointer.
+  } else {
+    assert(indices.empty());
+    indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty, 0));
+  }
+
+  assert(position >= Begin);
+  // We have to use i32 here because struct GEPs demand i32 indices.
+  // It's rather unlikely to matter in practice.
+  indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty,
+                                           position - Begin));
+}
+
+ConstantAggregateBuilderBase::PlaceholderPosition
+ConstantAggregateBuilderBase::addPlaceholderWithSize(llvm::Type *type) {
+  // Bring the offset up to the last field.
+  CharUnits offset = getNextOffsetFromGlobal();
+
+  // Create the placeholder.
+  auto position = addPlaceholder();
+
+  // Advance the offset past that field.
+  auto &layout = Builder.CGM.getDataLayout();
+  if (!Packed)
+    offset = offset.alignTo(CharUnits::fromQuantity(
+                                layout.getABITypeAlignment(type)));
+  offset += CharUnits::fromQuantity(layout.getTypeStoreSize(type));
+
+  CachedOffsetEnd = Builder.Buffer.size();
+  CachedOffsetFromGlobal = offset;
+
+  return position;
+}
+
+CharUnits ConstantAggregateBuilderBase::getOffsetFromGlobalTo(size_t end) const{
+  size_t cacheEnd = CachedOffsetEnd;
+  assert(cacheEnd <= end);
+
+  // Fast path: if the cache is valid, just use it.
+  if (cacheEnd == end) {
+    return CachedOffsetFromGlobal;
+  }
+
+  // If the cached range ends before the index at which the current
+  // aggregate starts, recurse for the parent.
+  CharUnits offset;
+  if (cacheEnd < Begin) {
+    assert(cacheEnd == 0);
+    assert(Parent && "Begin != 0 for root builder");
+    cacheEnd = Begin;
+    offset = Parent->getOffsetFromGlobalTo(Begin);
+  } else {
+    offset = CachedOffsetFromGlobal;
+  }
+
+  // Perform simple layout on the elements in cacheEnd..<end.
+  if (cacheEnd != end) {
+    auto &layout = Builder.CGM.getDataLayout();
+    do {
+      llvm::Constant *element = Builder.Buffer[cacheEnd];
+      assert(element != nullptr &&
+             "cannot compute offset when a placeholder is present");
+      llvm::Type *elementType = element->getType();
+      if (!Packed)
+        offset = offset.alignTo(CharUnits::fromQuantity(
+                                  layout.getABITypeAlignment(elementType)));
+      offset += CharUnits::fromQuantity(layout.getTypeStoreSize(elementType));
+    } while (++cacheEnd != end);
+  }
+
+  // Cache and return.
+  CachedOffsetEnd = cacheEnd;
+  CachedOffsetFromGlobal = offset;
+  return offset;
+}
+
+llvm::Constant *ConstantAggregateBuilderBase::finishArray(llvm::Type *eltTy) {
+  markFinished();
+
+  auto &buffer = getBuffer();
+  assert((Begin < buffer.size() ||
+          (Begin == buffer.size() && eltTy))
+         && "didn't add any array elements without element type");
+  auto elts = llvm::makeArrayRef(buffer).slice(Begin);
+  if (!eltTy) eltTy = elts[0]->getType();
+  auto type = llvm::ArrayType::get(eltTy, elts.size());
+  auto constant = llvm::ConstantArray::get(type, elts);
+  buffer.erase(buffer.begin() + Begin, buffer.end());
+  return constant;
+}
+
+llvm::Constant *
+ConstantAggregateBuilderBase::finishStruct(llvm::StructType *ty) {
+  markFinished();
+
+  auto &buffer = getBuffer();
+  auto elts = llvm::makeArrayRef(buffer).slice(Begin);
+
+  if (ty == nullptr && elts.empty())
+    ty = llvm::StructType::get(Builder.CGM.getLLVMContext(), {}, Packed);
+
+  llvm::Constant *constant;
+  if (ty) {
+    assert(ty->isPacked() == Packed);
+    constant = llvm::ConstantStruct::get(ty, elts);
+  } else {
+    constant = llvm::ConstantStruct::getAnon(elts, Packed);
+  }
+
+  buffer.erase(buffer.begin() + Begin, buffer.end());
+  return constant;
+}