Replace llc with clang -cc1 for invoking the SPIRV backend.

Author: mgcarrasco

clang/lib/Driver/ToolChains/HIPAMD.cpp

@@ -179,20 +179,19 @@ void AMDGCN::Linker::constructLinkAndEmitSpirvCommand(
       options::OPT_amdgpu_use_experimental_spirv_backend,
       options::OPT_no_amdgpu_use_experimental_spirv_backend, /*Default=*/false);
 
+  // Emit SPIR-V binary either using the SPIRV backend or the translator.
   if (UseSPIRVBackend) {
     llvm::opt::ArgStringList CmdArgs;
-    CmdArgs.push_back(LinkedBCFile.getFilename());
-    CmdArgs.append({"-o", Output.getFilename()});
-    const char *Exec =
-        C.getArgs().MakeArgString(getToolChain().GetProgramPath("llc"));
     const char *Triple =
-        C.getArgs().MakeArgString("-mtriple=" + getSpirvBackendTriple());
-    CmdArgs.push_back(Triple);
+        C.getArgs().MakeArgString("-triple=" + getSpirvBackendTriple());
+    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 {
-    // Emit SPIR-V binary.
+    // Use the SPIRV translator for code gen.
     llvm::opt::ArgStringList TrArgs{
         "--spirv-max-version=1.6",
         "--spirv-ext=+all",

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

@@ -1,8 +1,8 @@
 // COM: This test case validates the behavior of -amdgpu-use-experimental-spirv-backend
 
-// COM: Test that -amdgpu-use-experimental-spirv-backend calls llc with the SPIRV triple.
+// COM: Test that -amdgpu-use-experimental-spirv-backend calls clang -cc1 with the SPIRV triple.
 // RUN: %clang -x hip %s --cuda-device-only --offload-arch=amdgcnspirv -amdgpu-use-experimental-spirv-backend -nogpuinc -nogpulib -### 2>&1 | FileCheck %s --check-prefix=CHECK-SPIRV-BACKEND
-// CHECK-SPIRV-BACKEND: "{{.*}}llc{{.*}}" "{{-mtriple=spirv64v[0-9]+\.[0-9]+-amd-amdhsa}}"
+// CHECK-SPIRV-BACKEND: "{{.*}}clang{{.*}}" "-cc1" "{{.*-triple=spirv64v[0-9]+\.[0-9]+-amd-amdhsa}}"
 
 // COM: Test that -no-amdgpu-use-experimental-spirv-backend calls the SPIRV translator
 // RUN: %clang -x hip %s --cuda-device-only --offload-arch=amdgcnspirv -no-amdgpu-use-experimental-spirv-backend -nogpuinc -nogpulib -### 2>&1 | FileCheck %s --check-prefix=CHECK-SPIRV-TRANSLATOR