[DirectX][HLSL] Add /Qsource_in_debug_module to llc and Clang DXC driver

dx.source metadata nodes contain shader source code information, such as source
files content, macro definitions used to compile shader, and compiler
arguments.

PR for Clang to produce them is currently on review llvm/llvm-project#199689.

Original DXC has two modes to handle these nodes:
1. If /Qsource_in_debug_module is not specified, Source Info part (SRCI)
   is created inside shader's debug PDB file, and dx.source metadata
   nodes are replaced with empty nodes.
2. If /Qsource_in_debug_module is specified, dx.source nodes are
   preserved in debug bitcode module, for debug info consumers to
   use them directly.

This patch reimplements the behavior described in item 2.

/Qsource_in_debug_module is added to Clang DXC driver, and the
corresponding flag is added to llc. In DXILWriterPass, this flag
is used to determine how dx.source metadata nodes should be handled.

Author: dzhidzhoev

clang/include/clang/Options/Options.td

@@ -9624,6 +9624,11 @@ def dxc_Fc : DXCJoinedOrSeparate<"Fc">,
   HelpText<"Output assembly listing file">;
 def dxc_Frs : DXCJoinedOrSeparate<"Frs">,
   HelpText<"Output additional root signature object file">;
+def dxc_source_in_debug_module
+    : Option<["/", "-"], "Qsource_in_debug_module", KIND_FLAG>,
+      Group<dxc_Group>,
+      Visibility<[DXCOption]>,
+      HelpText<"Embed source code into debug module on DirectX target">;
 def dxil_validator_version : Option<["/", "-"], "validator-version", KIND_SEPARATE>,
   Group<dxc_Group>, Flags<[HelpHidden]>,
   Visibility<[DXCOption, ClangOption, CC1Option]>,

clang/lib/Driver/ToolChains/Clang.cpp

@@ -3832,6 +3832,11 @@ static void RenderHLSLOptions(const ArgList &Args, ArgStringList &CmdArgs,
   if (!Args.hasArg(options::OPT_dxc_no_stdinc) &&
       !Args.hasArg(options::OPT_nostdinc))
     CmdArgs.push_back("-finclude-default-header");
+
+  if (Args.hasArg(options::OPT_dxc_source_in_debug_module)) {
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("--dx-source-in-debug-module");
+  }
 }
 
 static void RenderOpenACCOptions(const Driver &D, const ArgList &Args,

clang/test/Driver/dxc_source_in_debug_module.hlsl

@@ -0,0 +1,6 @@
+// RUN: %clang_dxc -Tlib_6_7 -### /Zi /Qsource_in_debug_module %s 2>&1 | FileCheck %s
+// RUN: %clang_dxc -Tlib_6_7 -### /Zi -Qsource_in_debug_module %s 2>&1 | FileCheck %s
+// RUN: %clang_dxc -Tlib_6_7 -### /Zi %s 2>&1 | FileCheck %s --check-prefix=NOFLAG
+
+// CHECK: "-mllvm" "--dx-source-in-debug-module"
+// NOFLAG-NOT: --dx-source-in-debug-module

llvm/lib/Target/DirectX/DXILTranslateMetadata.cpp

@@ -514,15 +514,18 @@ static void cleanModuleFlags(Module &M) {
     M.addModuleFlag(Flag.Behavior, Flag.Key->getString(), Flag.Val);
 }
 
-using GlobalMDList = std::array<StringLiteral, 7>;
+using GlobalMDList = std::array<StringLiteral, 11>;
 
 // The following are compatible with DXIL but not emit with clang, they can
 // be added when applicable:
 // dx.typeAnnotations, dx.viewIDState, dx.dxrPayloadAnnotations
 static GlobalMDList CompatibleNamedModuleMDs = {
-    "llvm.ident",     "llvm.module.flags", "dx.resources",   "dx.valver",
-    "dx.shaderModel", "dx.version",        "dx.entryPoints",
-};
+    "llvm.ident",        "llvm.module.flags",
+    "dx.resources",      "dx.valver",
+    "dx.shaderModel",    "dx.version",
+    "dx.entryPoints",    "dx.source.contents",
+    "dx.source.defines", "dx.source.mainFileName",
+    "dx.source.args"};
 
 static void translateGlobalMetadata(Module &M, DXILResourceMap &DRM,
                                     DXILResourceTypeMap &DRTM,

llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp

@@ -28,11 +28,17 @@
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Alignment.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 
 using namespace llvm;
 using namespace llvm::dxil;
 
+static cl::opt<bool> SourceInDebugModule(
+    "dx-source-in-debug-module",
+    cl::desc("Embed source code into debug module on DirectX target"),
+    cl::init(false));
+
 namespace {
 class WriteDXILPass : public llvm::ModulePass {
   raw_ostream &OS; // raw_ostream to print on
@@ -138,6 +144,16 @@ static void removeLifetimeIntrinsics(Module &M) {
   }
 }
 
+static void replaceNamedMetadataArray(Module &M, StringRef Name,
+                                      ArrayRef<Metadata *> NewOps) {
+  NamedMDNode *NMD = M.getNamedMetadata(Name);
+  if (!NMD)
+    return;
+  NMD->eraseFromParent();
+  M.getOrInsertNamedMetadata(Name)->addOperand(
+      MDTuple::get(M.getContext(), NewOps));
+}
+
 class EmbedDXILPass : public llvm::ModulePass {
 public:
   static char ID; // Pass identification, replacement for typeid
@@ -155,6 +171,16 @@ class EmbedDXILPass : public llvm::ModulePass {
     // fail the Module Verifier if performed in an earlier pass
     legalizeLifetimeIntrinsics(M);
 
+    // Replace dx.source metadata nodes with stubs.
+    if (!SourceInDebugModule) {
+      LLVMContext &Ctx = M.getContext();
+      MDString *EmptyString = MDString::get(Ctx, "");
+      replaceNamedMetadataArray(M, "dx.source.contents",
+                                {EmptyString, EmptyString});
+      replaceNamedMetadataArray(M, "dx.source.defines", {});
+      replaceNamedMetadataArray(M, "dx.source.mainFileName", {EmptyString});
+      replaceNamedMetadataArray(M, "dx.source.args", {});
+    }
     const auto DIMap = DXILDebugInfoPass::run(M);
     WriteDXILToFile(M, OS, DIMap);
 

llvm/test/CodeGen/DirectX/ContainerData/SourceInfo-Strip.ll

@@ -0,0 +1,56 @@
+; Compare source info emission with and without --dx-source-in-debug-module flag.
+
+; RUN: llc %s --filetype=obj -o %t.dxbc
+; RUN: llvm-objcopy --dump-section=DXIL=%t.dxil.bc %t.dxbc
+; RUN: llvm-dis %t.dxil.bc -o - | FileCheck %s --check-prefix=ILDB-DIS
+
+; RUN: llc %s --filetype=obj -o %t.dxbc --dx-source-in-debug-module
+; RUN: llvm-objcopy --dump-section=DXIL=%t.dxil.bc %t.dxbc
+; RUN: llvm-dis %t.dxil.bc -o - | FileCheck %s --check-prefix=ILDB-SOURCE-DIS
+
+; Without the flag, dx.source should be replaced with dummy metadata.
+; ILDB-DIS: !dx.source.contents = !{![[CONTENTS:[0-9]+]]}
+; ILDB-DIS: !dx.source.defines = !{![[EMPTY_ARR:[0-9]+]]}
+; ILDB-DIS: !dx.source.mainFileName = !{![[MAIN:[0-9]+]]}
+; ILDB-DIS: !dx.source.args = !{![[EMPTY_ARR]]}
+; ILDB-DIS: ![[CONTENTS]] = !{!"", !""}
+; ILDB-DIS: ![[EMPTY_ARR]] = !{}
+; ILDB-DIS: ![[MAIN]] = !{!""}
+
+; With the flag, dx.source should be be preserved.
+; ILDB-SOURCE-DIS: !dx.source.args = !{![[ARGS:[0-9]+]]}
+; ILDB-SOURCE-DIS: !dx.source.contents = !{![[FILE1:[0-9]+]], ![[FILE2:[0-9]+]], ![[FILE3:[0-9]+]]}
+; ILDB-SOURCE-DIS: !dx.source.mainFileName = !{![[MAIN:[0-9]+]]}
+; ILDB-SOURCE-DIS: !dx.source.defines = !{![[DEFINES:[0-9]+]]}
+; ILDB-SOURCE-DIS: ![[FILE1]] = !{!"C:\\dx-source-metadata.hlsl",
+; ILDB-SOURCE-DIS: ![[FILE2]] = !{!"C:\\a.hlsl"
+; ILDB-SOURCE-DIS: ![[FILE3]] = !{!"C:\\b.hlsl"
+; ILDB-SOURCE-DIS: ![[MAIN]] = !{!"C:\\dx-source-metadata.hlsl"}
+; ILDB-SOURCE-DIS: ![[DEFINES]] = !{!"USER_DEF0=42", !"USER_DEF1=43"}
+
+target triple = "dxilv1.3-pc-shadermodel6.3-library"
+
+define float @_Z3fooff(float %a, float %b) {
+entry:
+  %add = fadd float %a, %b
+  ret float %add
+}
+
+!llvm.dbg.cu = !{!4}
+!llvm.module.flags = !{!6, !7}
+
+!dx.source.args = !{!0}
+!dx.source.contents = !{!1, !2, !3}
+!dx.source.mainFileName = !{!8}
+!dx.source.defines = !{!9}
+
+!0 = !{!"-g", !"-Tlib_6_3", !"-DUSER_DEF0=42", !"-DUSER_DEF1=43", !"C:\\\\dx-source-metadata.hlsl"}
+!1 = !{!"C:\\dx-source-metadata.hlsl", !"#include \22a.hlsl\22\0A#include \22b.hlsl\22\0A\0Afloat foo(float a, float b) {\0A  return a + b;\0A}\0A"}
+!2 = !{!"C:\\a.hlsl", !"#include \22b.hlsl\22\0A"}
+!3 = !{!"C:\\b.hlsl", !"#include <c.hlsl>\0A"}
+!4 = distinct !DICompileUnit(language: DW_LANG_C99, file: !5, emissionKind: FullDebug)
+!5 = !DIFile(filename: "dx-source-metadata.hlsl", directory: "C:\\")
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{!"C:\\dx-source-metadata.hlsl"}
+!9 = !{!"USER_DEF0=42", !"USER_DEF1=43"}