[Clang] Remove -no-opaque-pointers cc1 flag

[nikic]

Summary

Migration of clang tests to opaque pointers is finished, so remove the -no-opaque-pointers flag.

\o/

[aeubanks]

yay!

[dblaikie]

(I hope this doesn't come off as condescending/patronizing, I mean it quite genuinely)

A deep thanks to everyone who worked on this, especially @aeubanks and @nikic, and @t.p.northover - it's been a long project and I really appreciate you folks picking up where I stalled out years ago/paying down the technical debt I created (which I'm sorry about).
Starting with https://lists.llvm.org/pipermail/llvm-dev/2015-February/081822.html and the first change, I think, was D7655, so... 8 years, 4 months? Glad it's come along.

clang/docs/ReleaseNotes.rst

 -------------------------
 - The deprecated flag `-fmodules-ts` is removed. Please use ``-std=c++20``
   or higher to use standard C++ modules instead.
 - The deprecated flag `-fcoroutines-ts` is removed. Please use ``-std=c++20``
   or higher to use standard C++ coroutines instead.
 - The CodeGen flag `-lower-global-dtors-via-cxa-atexit` which affects how global
   destructors are lowered for MachO is removed without replacement. The default
   of `-lower-global-dtors-via-cxa-atexit=true` is now the only supported way.
+- The cc1 flag ``-no-opaque-pointers`` has been removed.
 
 Attribute Changes in Clang
 --------------------------
 - Introduced a new function attribute ``__attribute__((unsafe_buffer_usage))``
   to be worn by functions containing buffer operations that could cause out of
   bounds memory accesses. It emits warnings at call sites to such functions when
   the flag ``-Wunsafe-buffer-usage`` is enabled.
 - ``__declspec`` attributes can now be used together with the using keyword. Before

clang/include/clang/Basic/CodeGenOptions.def

 
 /// Whether to skip RAX setup when passing variable arguments (x86 only).
 CODEGENOPT(SkipRaxSetup, 1, 0)
 
 /// Whether to zero out caller-used registers before returning.
 ENUM_CODEGENOPT(ZeroCallUsedRegs, llvm::ZeroCallUsedRegs::ZeroCallUsedRegsKind,
                 5, llvm::ZeroCallUsedRegs::ZeroCallUsedRegsKind::Skip)
 
-/// Whether to use opaque pointers.
-CODEGENOPT(OpaquePointers, 1, 0)
-
 /// Modify C++ ABI to returning `this` pointer from constructors and
 /// non-deleting destructors. (No effect on Microsoft ABI.)
 CODEGENOPT(CtorDtorReturnThis, 1, 0)
 
 #undef CODEGENOPT
 #undef ENUM_CODEGENOPT
 #undef VALUE_CODEGENOPT

clang/include/clang/Driver/Options.td

defm clear_ast_before_backend : BoolOption<"",
   BothFlags<[], " the Clang AST before running backend code generation">>;
 defm enable_noundef_analysis : BoolOption<"",
   "enable-noundef-analysis",
   CodeGenOpts<"EnableNoundefAttrs">,
   DefaultTrue,
   PosFlag<SetTrue, [], "Enable">,
   NegFlag<SetFalse, [], "Disable">,
   BothFlags<[], " analyzing function argument and return types for mandatory definedness">>;
-defm opaque_pointers : BoolOption<"",
-  "opaque-pointers",
-  CodeGenOpts<"OpaquePointers">,
-  DefaultTrue,
-  PosFlag<SetTrue, [], "Enable">,
-  NegFlag<SetFalse, [], "Disable">,
-  BothFlags<[], " opaque pointers">>;
 def discard_value_names : Flag<["-"], "discard-value-names">,
   HelpText<"Discard value names in LLVM IR">,
   MarshallingInfoFlag<CodeGenOpts<"DiscardValueNames">>;
 def plugin_arg : JoinedAndSeparate<["-"], "plugin-arg-">,
     MetaVarName<"<name> <arg>">,
     HelpText<"Pass <arg> to plugin <name>">;
 def add_plugin : Separate<["-"], "add-plugin">, MetaVarName<"<name>">,
   HelpText<"Use the named plugin action in addition to the default action">,

clang/lib/CodeGen/CodeGenAction.cpp

CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   BackendAction BA = static_cast<BackendAction>(Act);
   std::unique_ptr<raw_pwrite_stream> OS = CI.takeOutputStream();
   if (!OS)
     OS = GetOutputStream(CI, InFile, BA);
 
   if (BA != Backend_EmitNothing && !OS)
     return nullptr;
 
-  VMContext->setOpaquePointers(CI.getCodeGenOpts().OpaquePointers);
-
   // Load bitcode modules to link with, if we need to.
   if (LinkModules.empty())
     for (const CodeGenOptions::BitcodeFileToLink &F :
          CI.getCodeGenOpts().LinkBitcodeFiles) {
       auto BCBuf = CI.getFileManager().getBufferForFile(F.Filename);
       if (!BCBuf) {
         CI.getDiagnostics().Report(diag::err_cannot_open_file)
             << F.Filename << BCBuf.getError().message();
CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   return std::move(Result);
 }
 
 std::unique_ptr<llvm::Module>
 CodeGenAction::loadModule(MemoryBufferRef MBRef) {
   CompilerInstance &CI = getCompilerInstance();
   SourceManager &SM = CI.getSourceManager();
 
-  VMContext->setOpaquePointers(CI.getCodeGenOpts().OpaquePointers);
-
   // For ThinLTO backend invocations, ensure that the context
   // merges types based on ODR identifiers. We also need to read
   // the correct module out of a multi-module bitcode file.
   if (!CI.getCodeGenOpts().ThinLTOIndexFile.empty()) {
     VMContext->enableDebugTypeODRUniquing();
 
     auto DiagErrors = [&](Error E) -> std::unique_ptr<llvm::Module> {
       unsigned DiagID =

clang/test/CodeGen/opaque-pointers-flag.c

-// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
-// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm %s -o - | FileCheck %s -check-prefix=TYPED
-// RUN: %clang_cc1 -opaque-pointers -triple x86_64-unknown-unknown -emit-llvm %s -o - | FileCheck %s -check-prefix=OPAQUE
-
-// TYPED-LABEL: @test(
-// TYPED-NEXT:  entry:
-// TYPED-NEXT:    [[P_ADDR:%.*]] = alloca ptr, align 8
-// TYPED-NEXT:    store ptr [[P:%.*]], ptr [[P_ADDR]], align 8
-// TYPED-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
-// TYPED-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[TMP0]], i64 1
-// TYPED-NEXT:    [[TMP1:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
-// TYPED-NEXT:    ret i32 [[TMP1]]
-//
-// OPAQUE-LABEL: @test(
-// OPAQUE-NEXT:  entry:
-// OPAQUE-NEXT:    [[P_ADDR:%.*]] = alloca ptr, align 8
-// OPAQUE-NEXT:    store ptr [[P:%.*]], ptr [[P_ADDR]], align 8
-// OPAQUE-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
-// OPAQUE-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[TMP0]], i64 1
-// OPAQUE-NEXT:    [[TMP1:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
-// OPAQUE-NEXT:    ret i32 [[TMP1]]
-//
-int test(int *p) {
-  return p[1];
-}

clang/test/CodeGenOpenCL/opaque-ptr-spirv.cl

-// RUN: %clang_cc1 -no-opaque-pointers -emit-llvm -o - -triple spirv64 %s | FileCheck %s
-
-// Check that we have a way to recover pointer
-// types for extern function prototypes (see PR56660).
-extern void foo(global int * ptr);
-kernel void k(global int * ptr) {
-  foo(ptr);
-}
-//CHECK: define spir_kernel void @k(i32 {{.*}}*
-//CHECK: declare spir_func void @foo(i32 {{.*}}*

llvm/docs/OpaquePointers.rst

 
 However, tests are still in the process of being converted to opaque pointers.
 As such, care must be taken when actively removing typed pointer support, to
 avoid breaking remaining tests.
 
 The following typed pointer functionality has already been removed:
 
 * The ``CLANG_ENABLE_OPAQUE_POINTERS`` cmake flag is no longer supported.
+* The ``-no-opaque-pointers`` cc1 clang flag is no longer supported.
+* The ``-plugin-opt=no-opaque-pointers`` LTO flag is no longer supported.
 * C APIs that do not support opaque pointers (like ``LLVMBuildLoad``) are no
   longer supported.
 * Typed pointer IR and bitcode is implicitly upgraded to use opaque pointers,
   unless ``-opaque-pointers=0`` is passed.
 
 The following typed pointer functionality is still to be removed:
 
-* The ``-no-opaque-pointers`` cc1 flag, ``-opaque-pointers=0`` opt flag and
-  ``-plugin-opt=no-opaque-pointers`` lto flag.
+* The ``-opaque-pointers=0`` opt flag.
 * Support for typed pointers in LLVM libraries.