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//===--- ConstantInitBuilder.cpp - Global initializer builder -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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::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);
entry.Dummy->replaceAllUsesWith(resolvedReference);
entry.Dummy->eraseFromParent();
}
}
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));
}
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();
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();
assert(Begin < buffer.size() && "didn't add any struct elements?");
auto elts = llvm::makeArrayRef(buffer).slice(Begin);
llvm::Constant *constant;
if (ty) {
constant = llvm::ConstantStruct::get(ty, elts);
} else {
constant = llvm::ConstantStruct::getAnon(elts, /*packed*/ false);
}
buffer.erase(buffer.begin() + Begin, buffer.end());
return constant;
}
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