[clang] [HLSL] Add the `Frs` `DXC` driver option (PR #157690)

[Finn Plummer via cfe-commits]

https://github.com/inbelic created https://github.com/llvm/llvm-project/pull/157690

This pr adds the `Frs` as a DXC driver option.

It is done by invoking `llvm-objcopy` with the `extract-section=RTS0`
argument specified to output the separate `DXContainer`.

This resolves: https://github.com/llvm/llvm-project/issues/150277.

>From 0831e99798973a6d8c47ef6b257046640298142c Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Tue, 9 Sep 2025 15:09:28 +0000
Subject: [PATCH 1/2] [HLSL] Add the `Frs` driver option

This pr adds the `Frs` as a DXC driver option.

It is done by invoking `llvm-objcopy` with the `extract-section=RTS0`
argument specified to output the separate `DXContainer`.

This resolves: .
---
 clang/include/clang/Driver/Options.td |  2 ++
 clang/lib/Driver/ToolChains/HLSL.cpp  |  9 ++++++++-
 clang/test/Driver/dxc_frs.hlsl        | 10 ++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/Driver/dxc_frs.hlsl

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index ea5a94f840470..123caa9d35520 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -9418,6 +9418,8 @@ def dxc_Fo : DXCJoinedOrSeparate<"Fo">,
   HelpText<"Output object file">;
 def dxc_Fc : DXCJoinedOrSeparate<"Fc">,
   HelpText<"Output assembly listing file">;
+def dxc_Frs : DXCJoinedOrSeparate<"Frs">,
+  HelpText<"Output additional root signature object file">;
 def dxil_validator_version : Option<["/", "-"], "validator-version", KIND_SEPARATE>,
   Group<dxc_Group>, Flags<[HelpHidden]>,
   Visibility<[DXCOption, ClangOption, CC1Option]>,
diff --git a/clang/lib/Driver/ToolChains/HLSL.cpp b/clang/lib/Driver/ToolChains/HLSL.cpp
index 559af32dc3808..179d7fc31ade9 100644
--- a/clang/lib/Driver/ToolChains/HLSL.cpp
+++ b/clang/lib/Driver/ToolChains/HLSL.cpp
@@ -317,6 +317,12 @@ void tools::hlsl::LLVMObjcopy::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(Frs);
   }
 
+  if (Arg *Arg = Args.getLastArg(options::OPT_dxc_Frs)) {
+    const char *Frs =
+        Args.MakeArgString("--extract-section=RTS0=" + Twine(Arg->getValue()));
+    CmdArgs.push_back(Frs);
+  }
+
   assert(CmdArgs.size() > 2 && "Unnecessary invocation of objcopy.");
 
   C.addCommand(std::make_unique<Command>(JA, *this, ResponseFileSupport::None(),
@@ -493,7 +499,8 @@ bool HLSLToolChain::requiresBinaryTranslation(DerivedArgList &Args) const {
 
 bool HLSLToolChain::requiresObjcopy(DerivedArgList &Args) const {
   return Args.hasArg(options::OPT_dxc_Fo) &&
-         Args.hasArg(options::OPT_dxc_strip_rootsignature);
+         (Args.hasArg(options::OPT_dxc_strip_rootsignature) ||
+          Args.hasArg(options::OPT_dxc_Frs));
 }
 
 bool HLSLToolChain::isLastJob(DerivedArgList &Args,
diff --git a/clang/test/Driver/dxc_frs.hlsl b/clang/test/Driver/dxc_frs.hlsl
new file mode 100644
index 0000000000000..7f7034f6fef89
--- /dev/null
+++ b/clang/test/Driver/dxc_frs.hlsl
@@ -0,0 +1,10 @@
+// RUN: %clang_dxc -T cs_6_0 /Fo %t.dxo /Frs %t.rs.dxo -### %s 2>&1 | FileCheck %s
+
+// Test to demonstrate that extracting the root signature to the specified
+// output file with /Frs.
+
+// CHECK: "{{.*}}llvm-objcopy{{(.exe)?}}" "{{.*}}.obj" "{{.*}}.dxo" "--extract-section=RTS0={{.*}}.rs.dxo"
+
+[shader("compute"), RootSignature("")]
+[numthreads(1,1,1)]
+void EmptyEntry() {}

>From 11c141f2c386cc78f9daa4d473ac9a35194cb0b7 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Tue, 9 Sep 2025 15:11:37 +0000
Subject: [PATCH 2/2] self-review: update old arg name

---
 clang/lib/Driver/ToolChains/HLSL.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/HLSL.cpp b/clang/lib/Driver/ToolChains/HLSL.cpp
index 179d7fc31ade9..1bb7aa02188f9 100644
--- a/clang/lib/Driver/ToolChains/HLSL.cpp
+++ b/clang/lib/Driver/ToolChains/HLSL.cpp
@@ -313,8 +313,8 @@ void tools::hlsl::LLVMObjcopy::ConstructJob(Compilation &C, const JobAction &JA,
   CmdArgs.push_back(Output.getFilename());
 
   if (Args.hasArg(options::OPT_dxc_strip_rootsignature)) {
-    const char *Frs = Args.MakeArgString("--remove-section=RTS0");
-    CmdArgs.push_back(Frs);
+    const char *StripRS = Args.MakeArgString("--remove-section=RTS0");
+    CmdArgs.push_back(StripRS);
   }
 
   if (Arg *Arg = Args.getLastArg(options::OPT_dxc_Frs)) {