Include getting generated struct offsets in CodegenABITypes

This change adds a new function, CodeGen::getFieldNumber, that
enables a user of clang's code generation to get the field number
in a generated LLVM IR struct that corresponds to a particular field
in a C struct.

It is important to expose this information in Clang's code generation
interface because there is no reasonable way for users of Clang's code
generation to get this information. In particular:

LLVM struct types do not include field names.
Clang adds a non-trivial amount of logic to the code generation of LLVM IR types for structs, in particular to handle padding and bit fields.

Patch by Michael Ferguson!

Differential Revision: https://reviews.llvm.org/D38473

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@315392 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 318 insertions, 1 deletions

diff --git a/include/clang/CodeGen/CodeGenABITypes.h b/include/clang/CodeGen/CodeGenABITypes.h
index 615e55c8b6..53619fa8ef 100644
--- a/include/clang/CodeGen/CodeGenABITypes.h
+++ b/include/clang/CodeGen/CodeGenABITypes.h
@@ -72,12 +72,19 @@ const CGFunctionInfo &arrangeFreeFunctionCall(CodeGenModule &CGM,
                                               FunctionType::ExtInfo info,
                                               RequiredArgs args);
 
-// Returns null if the function type is incomplete and can't be lowered.
+/// Returns null if the function type is incomplete and can't be lowered.
 llvm::FunctionType *convertFreeFunctionType(CodeGenModule &CGM,
                                             const FunctionDecl *FD);
 
 llvm::Type *convertTypeForMemory(CodeGenModule &CGM, QualType T);
 
+/// Given a non-bitfield struct field, return its index within the elements of
+/// the struct's converted type.  The returned index refers to a field number in
+/// the complete object type which is returned by convertTypeForMemory.  FD must
+/// be a field in RD directly (i.e. not an inherited field).
+unsigned getLLVMFieldNumber(CodeGenModule &CGM,
+                            const RecordDecl *RD, const FieldDecl *FD);
+
 }  // end namespace CodeGen
 }  // end namespace clang
 
diff --git a/lib/CodeGen/CodeGenABITypes.cpp b/lib/CodeGen/CodeGenABITypes.cpp
index 0735a9c3df..c152291b15 100644
--- a/lib/CodeGen/CodeGenABITypes.cpp
+++ b/lib/CodeGen/CodeGenABITypes.cpp
@@ -17,6 +17,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/CodeGen/CodeGenABITypes.h"
+#include "CGRecordLayout.h"
 #include "CodeGenModule.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
 #include "clang/Frontend/CodeGenOptions.h"
@@ -80,3 +81,9 @@ llvm::Type *
 CodeGen::convertTypeForMemory(CodeGenModule &CGM, QualType T) {
   return CGM.getTypes().ConvertTypeForMem(T);
 }
+
+unsigned CodeGen::getLLVMFieldNumber(CodeGenModule &CGM,
+                                     const RecordDecl *RD,
+                                     const FieldDecl *FD) {
+  return CGM.getTypes().getCGRecordLayout(RD).getLLVMFieldNo(FD);
+}
diff --git a/unittests/CodeGen/CMakeLists.txt b/unittests/CodeGen/CMakeLists.txt
index 289a8c630d..74ab2a7f18 100644
--- a/unittests/CodeGen/CMakeLists.txt
+++ b/unittests/CodeGen/CMakeLists.txt
@@ -6,6 +6,7 @@ set(LLVM_LINK_COMPONENTS
 add_clang_unittest(ClangCodeGenTests
   BufferSourceTest.cpp
   IncrementalProcessingTest.cpp
+  CodeGenExternalTest.cpp
   )
 
 target_link_libraries(ClangCodeGenTests
diff --git a/unittests/CodeGen/CodeGenExternalTest.cpp b/unittests/CodeGen/CodeGenExternalTest.cpp
new file mode 100644
index 0000000000..bcec3eab06
--- /dev/null
+++ b/unittests/CodeGen/CodeGenExternalTest.cpp
@@ -0,0 +1,302 @@
+//===- unittests/CodeGen/CodeGenExternalTest.cpp - test external CodeGen -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/GlobalDecl.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/CodeGen/CodeGenABITypes.h"
+#include "clang/CodeGen/ModuleBuilder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Parse/ParseAST.h"
+#include "clang/Sema/Sema.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace clang;
+
+namespace {
+
+// Mocks up a language using Clang code generation as a library and
+// tests some basic functionality there.
+//   - CodeGen->GetAddrOfGlobal
+//   - CodeGen::convertTypeForMemory
+//   - CodeGen::getLLVMFieldNumber
+
+static const bool DebugThisTest = false;
+
+// forward declarations
+struct MyASTConsumer;
+static void test_codegen_fns(MyASTConsumer *my);
+static bool test_codegen_fns_ran;
+
+// This forwards the calls to the Clang CodeGenerator
+// so that we can test CodeGen functions while it is open.
+// It accumulates toplevel decls in HandleTopLevelDecl and
+// calls test_codegen_fns() in HandleTranslationUnit
+// before forwarding that function to the CodeGenerator.
+
+struct MyASTConsumer : public ASTConsumer {
+  std::unique_ptr<CodeGenerator> Builder;
+  std::vector<Decl*> toplevel_decls;
+
+  MyASTConsumer(std::unique_ptr<CodeGenerator> Builder_in)
+    : ASTConsumer(), Builder(std::move(Builder_in))
+  {
+  }
+
+  ~MyASTConsumer() { }
+
+  void Initialize(ASTContext &Context) override;
+  void HandleCXXStaticMemberVarInstantiation(VarDecl *VD) override;
+  bool HandleTopLevelDecl(DeclGroupRef D) override;
+  void HandleInlineFunctionDefinition(FunctionDecl *D) override;
+  void HandleInterestingDecl(DeclGroupRef D) override;
+  void HandleTranslationUnit(ASTContext &Ctx) override;
+  void HandleTagDeclDefinition(TagDecl *D) override;
+  void HandleTagDeclRequiredDefinition(const TagDecl *D) override;
+  void HandleCXXImplicitFunctionInstantiation(FunctionDecl *D) override;
+  void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) override;
+  void HandleImplicitImportDecl(ImportDecl *D) override;
+  void CompleteTentativeDefinition(VarDecl *D) override;
+  void AssignInheritanceModel(CXXRecordDecl *RD) override;
+  void HandleVTable(CXXRecordDecl *RD) override;
+  ASTMutationListener *GetASTMutationListener() override;
+  ASTDeserializationListener *GetASTDeserializationListener() override;
+  void PrintStats() override;
+  bool shouldSkipFunctionBody(Decl *D) override;
+};
+
+void MyASTConsumer::Initialize(ASTContext &Context) {
+  Builder->Initialize(Context);
+}
+
+bool MyASTConsumer::HandleTopLevelDecl(DeclGroupRef DG) {
+
+  for (DeclGroupRef::iterator I = DG.begin(), E = DG.end(); I != E; ++I) {
+    toplevel_decls.push_back(*I);
+  }
+
+  return Builder->HandleTopLevelDecl(DG);
+}
+
+void MyASTConsumer::HandleInlineFunctionDefinition(FunctionDecl *D) {
+  Builder->HandleInlineFunctionDefinition(D);
+}
+
+void MyASTConsumer::HandleInterestingDecl(DeclGroupRef D) {
+  Builder->HandleInterestingDecl(D);
+}
+
+void MyASTConsumer::HandleTranslationUnit(ASTContext &Context) {
+  test_codegen_fns(this);
+  // HandleTranslationUnit can close the module
+  Builder->HandleTranslationUnit(Context);
+}
+
+void MyASTConsumer::HandleTagDeclDefinition(TagDecl *D) {
+  Builder->HandleTagDeclDefinition(D);
+}
+
+void MyASTConsumer::HandleTagDeclRequiredDefinition(const TagDecl *D) {
+  Builder->HandleTagDeclRequiredDefinition(D);
+}
+
+void MyASTConsumer::HandleCXXImplicitFunctionInstantiation(FunctionDecl *D) {
+  Builder->HandleCXXImplicitFunctionInstantiation(D);
+}
+
+void MyASTConsumer::HandleTopLevelDeclInObjCContainer(DeclGroupRef D) {
+  Builder->HandleTopLevelDeclInObjCContainer(D);
+}
+
+void MyASTConsumer::HandleImplicitImportDecl(ImportDecl *D) {
+  Builder->HandleImplicitImportDecl(D);
+}
+
+void MyASTConsumer::CompleteTentativeDefinition(VarDecl *D) {
+  Builder->CompleteTentativeDefinition(D);
+}
+
+void MyASTConsumer::AssignInheritanceModel(CXXRecordDecl *RD) {
+  Builder->AssignInheritanceModel(RD);
+}
+
+void MyASTConsumer::HandleCXXStaticMemberVarInstantiation(VarDecl *VD) {
+   Builder->HandleCXXStaticMemberVarInstantiation(VD);
+}
+
+void MyASTConsumer::HandleVTable(CXXRecordDecl *RD) {
+   Builder->HandleVTable(RD);
+ }
+
+ASTMutationListener *MyASTConsumer::GetASTMutationListener() {
+  return Builder->GetASTMutationListener();
+}
+
+ASTDeserializationListener *MyASTConsumer::GetASTDeserializationListener() {
+  return Builder->GetASTDeserializationListener();
+}
+
+void MyASTConsumer::PrintStats() {
+  Builder->PrintStats();
+}
+
+bool MyASTConsumer::shouldSkipFunctionBody(Decl *D) {
+  return Builder->shouldSkipFunctionBody(D);
+}
+
+const char TestProgram[] =
+    "struct mytest_struct { char x; short y; char p; long z; };\n"
+    "int mytest_fn(int x) { return x; }\n";
+
+// This function has the real test code here
+static void test_codegen_fns(MyASTConsumer *my) {
+
+  bool mytest_fn_ok = false;
+  bool mytest_struct_ok = false;
+
+  CodeGen::CodeGenModule &CGM = my->Builder->CGM();
+
+  for (auto decl : my->toplevel_decls ) {
+    if (FunctionDecl *fd = dyn_cast<FunctionDecl>(decl)) {
+      if (fd->getName() == "mytest_fn") {
+        Constant *c = my->Builder->GetAddrOfGlobal(GlobalDecl(fd), false);
+        // Verify that we got a function.
+        ASSERT_TRUE(c != NULL);
+        if (DebugThisTest) {
+          c->print(dbgs(), true);
+          dbgs() << "\n";
+        }
+        mytest_fn_ok = true;
+      }
+    } else if(clang::RecordDecl *rd = dyn_cast<RecordDecl>(decl)) {
+      if (rd->getName() == "mytest_struct") {
+        RecordDecl *def = rd->getDefinition();
+        ASSERT_TRUE(def != NULL);
+        const clang::Type *clangTy = rd->getCanonicalDecl()->getTypeForDecl();
+        ASSERT_TRUE(clangTy != NULL);
+        QualType qType = clangTy->getCanonicalTypeInternal();
+
+        // Check convertTypeForMemory
+        llvm::Type *llvmTy = CodeGen::convertTypeForMemory(CGM, qType);
+        ASSERT_TRUE(llvmTy != NULL);
+        if (DebugThisTest) {
+          llvmTy->print(dbgs(), true);
+          dbgs() << "\n";
+        }
+
+        llvm::CompositeType* structTy = dyn_cast<CompositeType>(llvmTy);
+        ASSERT_TRUE(structTy != NULL);
+
+        // Check getLLVMFieldNumber
+        FieldDecl *xField = NULL;
+        FieldDecl *yField = NULL;
+        FieldDecl *zField = NULL;
+
+        for (auto field : rd->fields()) {
+          if (field->getName() == "x") xField = field;
+          if (field->getName() == "y") yField = field;
+          if (field->getName() == "z") zField = field;
+        }
+
+        ASSERT_TRUE(xField != NULL);
+        ASSERT_TRUE(yField != NULL);
+        ASSERT_TRUE(zField != NULL);
+
+        unsigned x = CodeGen::getLLVMFieldNumber(CGM, rd, xField);
+        unsigned y = CodeGen::getLLVMFieldNumber(CGM, rd, yField);
+        unsigned z = CodeGen::getLLVMFieldNumber(CGM, rd, zField);
+
+        ASSERT_NE(x, y);
+        ASSERT_NE(y, z);
+
+        llvm::Type* xTy = structTy->getTypeAtIndex(x);
+        llvm::Type* yTy = structTy->getTypeAtIndex(y);
+        llvm::Type* zTy = structTy->getTypeAtIndex(z);
+
+        ASSERT_TRUE(xTy != NULL);
+        ASSERT_TRUE(yTy != NULL);
+        ASSERT_TRUE(zTy != NULL);
+
+        if (DebugThisTest) {
+          xTy->print(dbgs(), true);
+          dbgs() << "\n";
+          yTy->print(dbgs(), true);
+          dbgs() << "\n";
+          zTy->print(dbgs(), true);
+          dbgs() << "\n";
+        }
+
+        ASSERT_GE(xTy->getPrimitiveSizeInBits(), 1u);
+        ASSERT_GE(yTy->getPrimitiveSizeInBits(), 16u); // short is at least 16b
+        ASSERT_GE(zTy->getPrimitiveSizeInBits(), 32u); // long is at least 32b
+
+        mytest_struct_ok = true;
+      }
+    }
+  }
+
+  ASSERT_TRUE(mytest_fn_ok);
+  ASSERT_TRUE(mytest_struct_ok);
+
+  test_codegen_fns_ran = true;
+}
+
+TEST(CodeGenExternalTest, CodeGenExternalTest) {
+    LLVMContext Context;
+    CompilerInstance compiler;
+
+    compiler.createDiagnostics();
+    compiler.getLangOpts().CPlusPlus = 1;
+    compiler.getLangOpts().CPlusPlus11 = 1;
+
+    compiler.getTargetOpts().Triple = llvm::Triple::normalize(
+        llvm::sys::getProcessTriple());
+    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
+      compiler.getDiagnostics(),
+      std::make_shared<clang::TargetOptions>(
+        compiler.getTargetOpts())));
+
+    compiler.createFileManager();
+    compiler.createSourceManager(compiler.getFileManager());
+    compiler.createPreprocessor(clang::TU_Prefix);
+
+    compiler.createASTContext();
+
+
+    compiler.setASTConsumer(std::unique_ptr<ASTConsumer>(
+          new MyASTConsumer(std::unique_ptr<CodeGenerator>(
+             CreateLLVMCodeGen(compiler.getDiagnostics(),
+                               "MemoryTypesTest",
+                               compiler.getHeaderSearchOpts(),
+                               compiler.getPreprocessorOpts(),
+                               compiler.getCodeGenOpts(),
+                               Context)))));
+
+    compiler.createSema(clang::TU_Prefix, nullptr);
+
+    clang::SourceManager &sm = compiler.getSourceManager();
+    sm.setMainFileID(sm.createFileID(
+        llvm::MemoryBuffer::getMemBuffer(TestProgram), clang::SrcMgr::C_User));
+
+    clang::ParseAST(compiler.getSema(), false, false);
+
+    ASSERT_TRUE(test_codegen_fns_ran);
+}
+
+} // end anonymous namespace