1 //===--- ConstantInitBuilder.cpp - Global initializer builder -------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file defines out-of-line routines for building initializers for
10 // global variables, in particular the kind of globals that are implicitly
11 // introduced by various language ABIs.
13 //===----------------------------------------------------------------------===//
15 #include "clang/CodeGen/ConstantInitBuilder.h"
16 #include "CodeGenModule.h"
18 using namespace clang;
19 using namespace CodeGen;
21 llvm::Type *ConstantInitFuture::getType() const {
22 assert(Data && "dereferencing null future");
23 if (Data.is<llvm::Constant*>()) {
24 return Data.get<llvm::Constant*>()->getType();
26 return Data.get<ConstantInitBuilderBase*>()->Buffer[0]->getType();
30 void ConstantInitFuture::abandon() {
31 assert(Data && "abandoning null future");
32 if (auto builder = Data.dyn_cast<ConstantInitBuilderBase*>()) {
38 void ConstantInitFuture::installInGlobal(llvm::GlobalVariable *GV) {
39 assert(Data && "installing null future");
40 if (Data.is<llvm::Constant*>()) {
41 GV->setInitializer(Data.get<llvm::Constant*>());
43 auto &builder = *Data.get<ConstantInitBuilderBase*>();
44 assert(builder.Buffer.size() == 1);
45 builder.setGlobalInitializer(GV, builder.Buffer[0]);
46 builder.Buffer.clear();
52 ConstantInitBuilderBase::createFuture(llvm::Constant *initializer) {
53 assert(Buffer.empty() && "buffer not current empty");
54 Buffer.push_back(initializer);
55 return ConstantInitFuture(this);
58 // Only used in this file.
59 inline ConstantInitFuture::ConstantInitFuture(ConstantInitBuilderBase *builder)
61 assert(!builder->Frozen);
62 assert(builder->Buffer.size() == 1);
63 assert(builder->Buffer[0] != nullptr);
66 llvm::GlobalVariable *
67 ConstantInitBuilderBase::createGlobal(llvm::Constant *initializer,
68 const llvm::Twine &name,
71 llvm::GlobalValue::LinkageTypes linkage,
72 unsigned addressSpace) {
73 auto GV = new llvm::GlobalVariable(CGM.getModule(),
74 initializer->getType(),
79 /*insert before*/ nullptr,
80 llvm::GlobalValue::NotThreadLocal,
82 GV->setAlignment(alignment.getQuantity());
83 resolveSelfReferences(GV);
87 void ConstantInitBuilderBase::setGlobalInitializer(llvm::GlobalVariable *GV,
88 llvm::Constant *initializer){
89 GV->setInitializer(initializer);
91 if (!SelfReferences.empty())
92 resolveSelfReferences(GV);
95 void ConstantInitBuilderBase::resolveSelfReferences(llvm::GlobalVariable *GV) {
96 for (auto &entry : SelfReferences) {
97 llvm::Constant *resolvedReference =
98 llvm::ConstantExpr::getInBoundsGetElementPtr(
99 GV->getValueType(), GV, entry.Indices);
100 auto dummy = entry.Dummy;
101 dummy->replaceAllUsesWith(resolvedReference);
102 dummy->eraseFromParent();
104 SelfReferences.clear();
107 void ConstantInitBuilderBase::abandon(size_t newEnd) {
108 // Remove all the entries we've added.
109 Buffer.erase(Buffer.begin() + newEnd, Buffer.end());
111 // If we're abandoning all the way to the beginning, destroy
112 // all the self-references, because we might not get another
115 for (auto &entry : SelfReferences) {
116 auto dummy = entry.Dummy;
117 dummy->replaceAllUsesWith(llvm::UndefValue::get(dummy->getType()));
118 dummy->eraseFromParent();
120 SelfReferences.clear();
124 void ConstantAggregateBuilderBase::addSize(CharUnits size) {
125 add(Builder.CGM.getSize(size));
129 ConstantAggregateBuilderBase::getRelativeOffset(llvm::IntegerType *offsetType,
130 llvm::Constant *target) {
131 // Compute the address of the relative-address slot.
132 auto base = getAddrOfCurrentPosition(offsetType);
135 base = llvm::ConstantExpr::getPtrToInt(base, Builder.CGM.IntPtrTy);
136 target = llvm::ConstantExpr::getPtrToInt(target, Builder.CGM.IntPtrTy);
137 llvm::Constant *offset = llvm::ConstantExpr::getSub(target, base);
139 // Truncate to the relative-address type if necessary.
140 if (Builder.CGM.IntPtrTy != offsetType) {
141 offset = llvm::ConstantExpr::getTrunc(offset, offsetType);
148 ConstantAggregateBuilderBase::getAddrOfCurrentPosition(llvm::Type *type) {
149 // Make a global variable. We will replace this with a GEP to this
150 // position after installing the initializer.
152 new llvm::GlobalVariable(Builder.CGM.getModule(), type, true,
153 llvm::GlobalVariable::PrivateLinkage,
155 Builder.SelfReferences.emplace_back(dummy);
156 auto &entry = Builder.SelfReferences.back();
157 (void) getGEPIndicesToCurrentPosition(entry.Indices);
161 void ConstantAggregateBuilderBase::getGEPIndicesTo(
162 llvm::SmallVectorImpl<llvm::Constant*> &indices,
163 size_t position) const {
164 // Recurse on the parent builder if present.
166 Parent->getGEPIndicesTo(indices, Begin);
168 // Otherwise, add an index to drill into the first level of pointer.
170 assert(indices.empty());
171 indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty, 0));
174 assert(position >= Begin);
175 // We have to use i32 here because struct GEPs demand i32 indices.
176 // It's rather unlikely to matter in practice.
177 indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty,
181 ConstantAggregateBuilderBase::PlaceholderPosition
182 ConstantAggregateBuilderBase::addPlaceholderWithSize(llvm::Type *type) {
183 // Bring the offset up to the last field.
184 CharUnits offset = getNextOffsetFromGlobal();
186 // Create the placeholder.
187 auto position = addPlaceholder();
189 // Advance the offset past that field.
190 auto &layout = Builder.CGM.getDataLayout();
192 offset = offset.alignTo(CharUnits::fromQuantity(
193 layout.getABITypeAlignment(type)));
194 offset += CharUnits::fromQuantity(layout.getTypeStoreSize(type));
196 CachedOffsetEnd = Builder.Buffer.size();
197 CachedOffsetFromGlobal = offset;
202 CharUnits ConstantAggregateBuilderBase::getOffsetFromGlobalTo(size_t end) const{
203 size_t cacheEnd = CachedOffsetEnd;
204 assert(cacheEnd <= end);
206 // Fast path: if the cache is valid, just use it.
207 if (cacheEnd == end) {
208 return CachedOffsetFromGlobal;
211 // If the cached range ends before the index at which the current
212 // aggregate starts, recurse for the parent.
214 if (cacheEnd < Begin) {
215 assert(cacheEnd == 0);
216 assert(Parent && "Begin != 0 for root builder");
218 offset = Parent->getOffsetFromGlobalTo(Begin);
220 offset = CachedOffsetFromGlobal;
223 // Perform simple layout on the elements in cacheEnd..<end.
224 if (cacheEnd != end) {
225 auto &layout = Builder.CGM.getDataLayout();
227 llvm::Constant *element = Builder.Buffer[cacheEnd];
228 assert(element != nullptr &&
229 "cannot compute offset when a placeholder is present");
230 llvm::Type *elementType = element->getType();
232 offset = offset.alignTo(CharUnits::fromQuantity(
233 layout.getABITypeAlignment(elementType)));
234 offset += CharUnits::fromQuantity(layout.getTypeStoreSize(elementType));
235 } while (++cacheEnd != end);
239 CachedOffsetEnd = cacheEnd;
240 CachedOffsetFromGlobal = offset;
244 llvm::Constant *ConstantAggregateBuilderBase::finishArray(llvm::Type *eltTy) {
247 auto &buffer = getBuffer();
248 assert((Begin < buffer.size() ||
249 (Begin == buffer.size() && eltTy))
250 && "didn't add any array elements without element type");
251 auto elts = llvm::makeArrayRef(buffer).slice(Begin);
252 if (!eltTy) eltTy = elts[0]->getType();
253 auto type = llvm::ArrayType::get(eltTy, elts.size());
254 auto constant = llvm::ConstantArray::get(type, elts);
255 buffer.erase(buffer.begin() + Begin, buffer.end());
260 ConstantAggregateBuilderBase::finishStruct(llvm::StructType *ty) {
263 auto &buffer = getBuffer();
264 auto elts = llvm::makeArrayRef(buffer).slice(Begin);
266 if (ty == nullptr && elts.empty())
267 ty = llvm::StructType::get(Builder.CGM.getLLVMContext(), {}, Packed);
269 llvm::Constant *constant;
271 assert(ty->isPacked() == Packed);
272 constant = llvm::ConstantStruct::get(ty, elts);
274 constant = llvm::ConstantStruct::getAnon(elts, Packed);
277 buffer.erase(buffer.begin() + Begin, buffer.end());