[codeview] Expose -gcodeview-ghash for global type hashing

Summary:
Experience has shown that the functionality is useful. It makes linking
optimized clang with debug info for me a lot faster, 20s to 13s. The
type merging phase of PDB writing goes from 10s to 3s.

This removes the LLVM cl::opt and replaces it with a metadata flag.

After this change, users can do the following to use ghash:
- add -gcodeview-ghash to compiler flags
- replace /DEBUG with /DEBUG:GHASH in linker flags

Reviewers: zturner, hans, thakis, takuto.ikuta

Subscribers: aprantl, hiraditya, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D54370

llvm-svn: 347072

clang/include/clang/Driver/Options.td

@@ -1818,9 +1818,15 @@ def gdwarf_4 : Flag<["-"], "gdwarf-4">, Group<g_Group>,
   HelpText<"Generate source-level debug information with dwarf version 4">;
 def gdwarf_5 : Flag<["-"], "gdwarf-5">, Group<g_Group>,
   HelpText<"Generate source-level debug information with dwarf version 5">;
+
 def gcodeview : Flag<["-"], "gcodeview">,
   HelpText<"Generate CodeView debug information">,
   Flags<[CC1Option, CC1AsOption, CoreOption]>;
+def gcodeview_ghash : Flag<["-"], "gcodeview-ghash">,
+  HelpText<"Emit type record hashes in a .debug$H section">,
+  Flags<[CC1Option, CoreOption]>;
+def gno_codeview_ghash : Flag<["-"], "gno-codeview-ghash">, Flags<[CoreOption]>;
+
 // Equivalent to our default dwarf version. Forces usual dwarf emission when
 // CodeView is enabled.
 def gdwarf : Flag<["-"], "gdwarf">, Alias<gdwarf_4>, Flags<[CoreOption]>;

clang/include/clang/Frontend/CodeGenOptions.def

@@ -297,6 +297,9 @@ VALUE_CODEGENOPT(DwarfVersion, 3, 0)
 /// CodeView and DWARF into the same object.
 CODEGENOPT(EmitCodeView, 1, 0)
 
+/// Whether to emit the .debug$H section containing hashes of CodeView types.
+CODEGENOPT(CodeViewGHash, 1, 0)
+
 /// The kind of inlining to perform.
 ENUM_CODEGENOPT(Inlining, InliningMethod, 2, NormalInlining)
 

clang/lib/CodeGen/CodeGenModule.cpp

@@ -458,6 +458,9 @@ void CodeGenModule::Release() {
     // Indicate that we want CodeView in the metadata.
     getModule().addModuleFlag(llvm::Module::Warning, "CodeView", 1);
   }
+  if (CodeGenOpts.CodeViewGHash) {
+    getModule().addModuleFlag(llvm::Module::Warning, "CodeViewGHash", 1);
+  }
   if (CodeGenOpts.ControlFlowGuard) {
     // We want function ID tables for Control Flow Guard.
     getModule().addModuleFlag(llvm::Module::Warning, "cfguardtable", 1);

clang/lib/Driver/ToolChains/Clang.cpp

@@ -3198,9 +3198,16 @@ static void RenderDebugOptions(const ToolChain &TC, const Driver &D,
       CmdArgs.push_back("-gembed-source");
   }
 
-  if (EmitCodeView)
+  if (EmitCodeView) {
     CmdArgs.push_back("-gcodeview");
 
+    // Emit codeview type hashes if requested.
+    if (Args.hasFlag(options::OPT_gcodeview_ghash,
+                     options::OPT_gno_codeview_ghash, false)) {
+      CmdArgs.push_back("-gcodeview-ghash");
+    }
+  }
+
   RenderDebugEnablingArgs(Args, CmdArgs, DebugInfoKind, DWARFVersion,
                           DebuggerTuning);
 

clang/lib/Frontend/CompilerInvocation.cpp

@@ -593,6 +593,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.DwarfVersion = getLastArgIntValue(Args, OPT_dwarf_version_EQ, 0, Diags);
   Opts.DebugColumnInfo = Args.hasArg(OPT_dwarf_column_info);
   Opts.EmitCodeView = Args.hasArg(OPT_gcodeview);
+  Opts.CodeViewGHash = Args.hasArg(OPT_gcodeview_ghash);
   Opts.MacroDebugInfo = Args.hasArg(OPT_debug_info_macro);
   Opts.WholeProgramVTables = Args.hasArg(OPT_fwhole_program_vtables);
   Opts.LTOVisibilityPublicStd = Args.hasArg(OPT_flto_visibility_public_std);

clang/test/CodeGenCXX/debug-info-ms-abi.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -triple=i686-pc-windows-msvc -debug-info-kind=limited -gcodeview -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -triple=i686-pc-windows-msvc -debug-info-kind=limited -gcodeview -gcodeview-ghash -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,GHASH
 
 // Tests that certain miscellaneous features work in the MS ABI.
 
@@ -45,3 +46,6 @@ Foo::Nested n;
 // CHECK-NEXT: ![[dummy:[0-9]+]] = !DISubroutineType(types: ![[Signature:[0-9]+]])
 // CHECK: ![[Signature]] = !{null, ![[BasicInt:[0-9]+]], ![[BasicInt]]}
 // CHECK: ![[BasicInt]] = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+
+// CHECK: !{{[0-9]+}} = !{i32 2, !"CodeView", i32 1}
+// GHASH: !{{[0-9]+}} = !{i32 2, !"CodeViewGHash", i32 1}

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

@@ -92,9 +92,6 @@
 using namespace llvm;
 using namespace llvm::codeview;
 
-static cl::opt<bool> EmitDebugGlobalHashes("emit-codeview-ghash-section",
-                                           cl::ReallyHidden, cl::init(false));
-
 static CPUType mapArchToCVCPUType(Triple::ArchType Type) {
   switch (Type) {
   case Triple::ArchType::x86:
@@ -125,6 +122,11 @@ CodeViewDebug::CodeViewDebug(AsmPrinter *AP)
 
   TheCPU =
       mapArchToCVCPUType(Triple(MMI->getModule()->getTargetTriple()).getArch());
+
+  // Check if we should emit type record hashes.
+  ConstantInt *GH = mdconst::extract_or_null<ConstantInt>(
+      MMI->getModule()->getModuleFlag("CodeViewGHash"));
+  EmitDebugGlobalHashes = GH && !GH->isZero();
 }
 
 StringRef CodeViewDebug::getFullFilepath(const DIFile *File) {

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h

@@ -54,6 +54,9 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   BumpPtrAllocator Allocator;
   codeview::GlobalTypeTableBuilder TypeTable;
 
+  /// Whether to emit type record hashes into .debug$H.
+  bool EmitDebugGlobalHashes = false;
+
   /// The codeview CPU type used by the translation unit.
   codeview::CPUType TheCPU;
 

llvm/test/DebugInfo/COFF/global-type-hashes.ll

@@ -1,7 +1,6 @@
-; RUN: llc -filetype=obj -emit-codeview-ghash-section < %s > %t.obj
+; RUN: llc -filetype=obj < %s > %t.obj
 ; RUN: obj2yaml %t.obj | FileCheck %s --check-prefix=YAML
-; RUN: llc -filetype=asm -emit-codeview-ghash-section < %s \
-; RUN:   | FileCheck %s --check-prefix=ASM
+; RUN: llc -filetype=asm < %s | FileCheck %s --check-prefix=ASM
 
 ; C++ source to regenerate:
 ; $ cat t.cpp
@@ -96,14 +95,16 @@ attributes #1 = { nounwind readnone speculatable }
 attributes #2 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-features"="+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
 !llvm.dbg.cu = !{!0}
-!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.module.flags = !{!3, !4, !5, !6, !100}
 !llvm.ident = !{!7}
 
+
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
 !1 = !DIFile(filename: "<stdin>", directory: "D:\5Csrc\5Cllvmbuild\5Cclang\5CDebug\5Cx86", checksumkind: CSK_MD5, checksum: "6279449503d9075c38e615e8387667c3")
 !2 = !{}
 !3 = !{i32 1, !"NumRegisterParameters", i32 0}
 !4 = !{i32 2, !"CodeView", i32 1}
+!100 = !{i32 2, !"CodeViewGHash", i32 1}
 !5 = !{i32 2, !"Debug Info Version", i32 3}
 !6 = !{i32 1, !"wchar_size", i32 2}
 !7 = !{!"clang version 6.0.0 "}