forked from OSchip/llvm-project
Allow the type of a global to be different from the type of its
associated declaration. This is a prerequisite to handling general union initializations; for example, an array of unions involving pointers has to be turned into a struct because the elements can have incompatible types. I refactored the code a bit to make it more readable; now, the logic for definitions is all in EmitGlobalVarInit. The second parameter for GetAddrOfGlobalVar is now dead; I'll remove it separately. By itself, this patch should not cause any visible changes. llvm-svn: 51783
This commit is contained in:
Eli Friedman
parent
48b9f4be9d
commit
c18d9d53bb
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@ -246,20 +246,15 @@ llvm::Constant *CodeGenModule::GetAddrOfFunctionDecl(const FunctionDecl *D,
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return Entry = NewFn;
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}
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static bool IsZeroElementArray(const llvm::Type *Ty) {
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if (const llvm::ArrayType *ATy = dyn_cast<llvm::ArrayType>(Ty))
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return ATy->getNumElements() == 0;
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return false;
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}
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llvm::Constant *CodeGenModule::GetAddrOfGlobalVar(const VarDecl *D,
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bool isDefinition) {
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assert(D->hasGlobalStorage() && "Not a global variable");
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assert(!isDefinition && "This shouldn't be called for definitions!");
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// See if it is already in the map.
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llvm::Constant *&Entry = GlobalDeclMap[D];
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if (Entry) return Entry;
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QualType ASTTy = D->getType();
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const llvm::Type *Ty = getTypes().ConvertTypeForMem(ASTTy);
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@ -273,53 +268,11 @@ llvm::Constant *CodeGenModule::GetAddrOfGlobalVar(const VarDecl *D,
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0, D->getName(), &getModule(), 0,
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ASTTy.getAddressSpace());
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}
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// If the pointer type matches, just return it.
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llvm::Type *PTy = llvm::PointerType::getUnqual(Ty);
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if (PTy == GV->getType()) return Entry = GV;
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// If this isn't a definition, just return it casted to the right type.
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if (!isDefinition)
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return Entry = llvm::ConstantExpr::getBitCast(GV, PTy);
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// Otherwise, we have a definition after a prototype with the wrong type.
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// GV is the GlobalVariable* for the one with the wrong type, we must make a
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/// new GlobalVariable* and update everything that used GV (a declaration)
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// with the new GlobalVariable* (which will be a definition).
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//
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// This happens if there is a prototype for a global (e.g. "extern int x[];")
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// and then a definition of a different type (e.g. "int x[10];"). Start by
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// making a new global of the correct type, RAUW, then steal the name.
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llvm::GlobalVariable *NewGV =
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new llvm::GlobalVariable(Ty, false, llvm::GlobalValue::ExternalLinkage,
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0, D->getName(), &getModule(), 0,
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ASTTy.getAddressSpace());
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NewGV->takeName(GV);
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// Replace uses of GV with the globalvalue we will endow with a body.
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llvm::Constant *NewPtrForOldDecl =
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llvm::ConstantExpr::getBitCast(NewGV, GV->getType());
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GV->replaceAllUsesWith(NewPtrForOldDecl);
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// FIXME: Update the globaldeclmap for the previous decl of this name. We
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// really want a way to walk all of these, but we don't have it yet. This
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// is incredibly slow!
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ReplaceMapValuesWith(GV, NewPtrForOldDecl);
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// Verify that GV was a declaration or something like x[] which turns into
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// [0 x type].
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assert((GV->isDeclaration() ||
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IsZeroElementArray(GV->getType()->getElementType())) &&
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"Shouldn't replace non-declaration");
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// Ok, delete the old global now, which is dead.
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GV->eraseFromParent();
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// Return the new global which has the right type.
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return Entry = NewGV;
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}
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// Otherwise, it already exists; return the existing version
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llvm::PointerType *PTy = llvm::PointerType::get(Ty, ASTTy.getAddressSpace());
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return Entry = llvm::ConstantExpr::getBitCast(GV, PTy);
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}
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void CodeGenModule::EmitObjCMethod(const ObjCMethodDecl *OMD) {
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// If this is not a prototype, emit the body.
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@ -449,23 +402,65 @@ void CodeGenModule::EmitGlobalVar(const VarDecl *D) {
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}
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void CodeGenModule::EmitGlobalVarInit(const VarDecl *D) {
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// Get the global, forcing it to be a direct reference.
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llvm::GlobalVariable *GV =
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cast<llvm::GlobalVariable>(GetAddrOfGlobalVar(D, true));
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// Convert the initializer, or use zero if appropriate.
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assert(D->hasGlobalStorage() && "Not a global variable");
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llvm::Constant *Init = 0;
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QualType ASTTy = D->getType();
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const llvm::Type *VarTy = getTypes().ConvertTypeForMem(ASTTy);
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const llvm::Type *VarPtrTy =
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llvm::PointerType::get(VarTy, ASTTy.getAddressSpace());
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if (D->getInit() == 0) {
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Init = llvm::Constant::getNullValue(GV->getType()->getElementType());
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} else if (D->getType()->isIntegerType()) {
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llvm::APSInt Value(static_cast<uint32_t>(
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getContext().getTypeSize(D->getInit()->getType())));
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if (D->getInit()->isIntegerConstantExpr(Value, Context))
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Init = llvm::ConstantInt::get(Value);
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Init = llvm::Constant::getNullValue(VarTy);
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} else {
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Init = EmitGlobalInit(D->getInit());
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}
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const llvm::Type* InitType = Init->getType();
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llvm::GlobalVariable *GV = getModule().getGlobalVariable(D->getName(), true);
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if (!GV) {
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GV = new llvm::GlobalVariable(InitType, false,
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llvm::GlobalValue::ExternalLinkage,
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0, D->getName(), &getModule(), 0,
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ASTTy.getAddressSpace());
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} else if (GV->getType()->getElementType() != InitType ||
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GV->getType()->getAddressSpace() != ASTTy.getAddressSpace()) {
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// We have a definition after a prototype with the wrong type.
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// We must make a new GlobalVariable* and update everything that used OldGV
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// (a declaration or tentative definition) with the new GlobalVariable*
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// (which will be a definition).
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//
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// This happens if there is a prototype for a global (e.g. "extern int x[];")
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// and then a definition of a different type (e.g. "int x[10];"). This also
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// happens when an initializer has a different type from the type of the
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// global (this happens with unions).
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// Save the old global
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llvm::GlobalVariable *OldGV = GV;
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// Make a new global with the correct type
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GV = new llvm::GlobalVariable(InitType, false,
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llvm::GlobalValue::ExternalLinkage,
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0, D->getName(), &getModule(), 0,
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ASTTy.getAddressSpace());
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// Steal the name of the old global
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GV->takeName(OldGV);
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// Replace all uses of the old global with the new global
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llvm::Constant *NewPtrForOldDecl =
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llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
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OldGV->replaceAllUsesWith(NewPtrForOldDecl);
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// Make sure we don't keep around any stale references to globals
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// FIXME: This is really slow; we need a better way to walk all
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// the decls with the same name
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ReplaceMapValuesWith(OldGV, NewPtrForOldDecl);
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// Erase the old global, since it is no longer used.
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OldGV->eraseFromParent();
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}
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if (!Init)
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Init = EmitGlobalInit(D->getInit());
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GlobalDeclMap[D] = llvm::ConstantExpr::getBitCast(GV, VarPtrTy);
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if (const AnnotateAttr *AA = D->getAttr<AnnotateAttr>()) {
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SourceManager &SM = Context.getSourceManager();
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@ -473,8 +468,6 @@ void CodeGenModule::EmitGlobalVarInit(const VarDecl *D) {
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SM.getLogicalLineNumber(D->getLocation())));
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}
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assert(GV->getType()->getElementType() == Init->getType() &&
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"Initializer codegen type mismatch!");
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GV->setInitializer(Init);
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unsigned Align = Context.getTypeAlign(D->getType());
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