[HIP][SPIRV] Enable the SPIRV backend instead of the translator through an experimental flag.

clang/include/clang/Driver/Options.td

@@ -1421,6 +1421,18 @@ def fhip_emit_relocatable : Flag<["-"], "fhip-emit-relocatable">,
   HelpText<"Compile HIP source to relocatable">;
 def fno_hip_emit_relocatable : Flag<["-"], "fno-hip-emit-relocatable">,
   HelpText<"Do not override toolchain to compile HIP source to relocatable">;
+def hip_use_experimental_spirv_backend
+    : Flag<["-"], "hip-use-experimental-spirv-backend">,
+      Group<hip_Group>,
+      Flags<[HelpHidden]>,
+      HelpText<"Use experimental SPIRV backend for HIP compilation (HIP "
+               "only)">;
+def no_hip_use_experimental_spirv_backend
+    : Flag<["-"], "no-hip-use-experimental-spirv-backend">,
+      Group<hip_Group>,
+      Flags<[HelpHidden]>,
+      HelpText<"Do not use experimental SPIRV backend for HIP compilation "
+               "(HIP only)">;
 }
 
 // Clang specific/exclusive options for OpenACC.

clang/lib/Driver/ToolChains/HIPAMD.cpp

@@ -175,15 +175,33 @@ void AMDGCN::Linker::constructLinkAndEmitSpirvCommand(
 
   constructLlvmLinkCommand(C, JA, Inputs, LinkedBCFile, Args);
 
-  // Emit SPIR-V binary.
-  llvm::opt::ArgStringList TrArgs{
-      "--spirv-max-version=1.6",
-      "--spirv-ext=+all",
-      "--spirv-allow-unknown-intrinsics",
-      "--spirv-lower-const-expr",
-      "--spirv-preserve-auxdata",
-      "--spirv-debug-info-version=nonsemantic-shader-200"};
-  SPIRV::constructTranslateCommand(C, *this, JA, Output, LinkedBCFile, TrArgs);
+  bool UseSPIRVBackend = Args.hasFlag(
+      options::OPT_hip_use_experimental_spirv_backend,
+      options::OPT_no_hip_use_experimental_spirv_backend, /*Default=*/false);
+
+  // Emit SPIR-V binary either using the SPIRV backend or the translator.
+  if (UseSPIRVBackend) {
+    llvm::opt::ArgStringList CmdArgs;
+    const char *Triple =
+        C.getArgs().MakeArgString("-triple=spirv64-amd-amdhsa");
+    CmdArgs.append({"-cc1", Triple, "-emit-obj", LinkedBCFile.getFilename(),
+                    "-o", Output.getFilename()});
+    const char *Exec = getToolChain().getDriver().getClangProgramPath();
+    C.addCommand(std::make_unique<Command>(JA, *this,
+                                           ResponseFileSupport::None(), Exec,
+                                           CmdArgs, LinkedBCFile, Output));
+  } else {
+    // Use the SPIRV translator for code gen.
+    llvm::opt::ArgStringList TrArgs{
+        "--spirv-max-version=1.6",
+        "--spirv-ext=+all",
+        "--spirv-allow-unknown-intrinsics",
+        "--spirv-lower-const-expr",
+        "--spirv-preserve-auxdata",
+        "--spirv-debug-info-version=nonsemantic-shader-200"};
+    SPIRV::constructTranslateCommand(C, *this, JA, Output, LinkedBCFile,
+                                     TrArgs);
+  }
 }
 
 // For amdgcn the inputs of the linker job are device bitcode and output is

clang/test/Driver/hip-spirv-backend-opt.c

@@ -0,0 +1,12 @@
+// COM: This test case validates the behavior of -hip-use-experimental-spirv-backend
+
+// COM: Test that -hip-use-experimental-spirv-backend calls clang -cc1 with the SPIRV triple.
+// RUN: %clang -x hip %s --cuda-device-only --offload-arch=amdgcnspirv -hip-use-experimental-spirv-backend -nogpuinc -nogpulib -### 2>&1 | FileCheck %s --check-prefix=CHECK-SPIRV-BACKEND
+// CHECK-SPIRV-BACKEND: "{{.*}}clang{{.*}}" "-cc1" "{{.*-triple=spirv64-amd-amdhsa}}"
+
+// COM: Test that -no-hip-use-experimental-spirv-backend calls the SPIRV translator
+// RUN: %clang -x hip %s --cuda-device-only --offload-arch=amdgcnspirv -no-hip-use-experimental-spirv-backend -nogpuinc -nogpulib -### 2>&1 | FileCheck %s --check-prefix=CHECK-SPIRV-TRANSLATOR
+// CHECK-SPIRV-TRANSLATOR: "{{.*llvm-spirv.*}}" "{{--spirv-max-version=[0-9]+\.[0-9]}}"
+
+// COM: Test that by default we use the translator
+// RUN: %clang -x hip %s --cuda-device-only --offload-arch=amdgcnspirv -nogpuinc -nogpulib -### 2>&1 | FileCheck %s --check-prefix=CHECK-SPIRV-TRANSLATOR