[clang] [llvm] [HIPSPV] Add in-tree SPIR-V backend support for chipStar (PR #186972)

[Henry Linjamäki via cfe-commits]

================
@@ -73,10 +77,55 @@ void HIPSPV::Linker::constructLinkAndEmitSpirvCommand(
   tools::constructLLVMLinkCommand(C, *this, JA, Inputs, LinkArgs, Output, Args,
                                   TempFile);
 
-  // Post-link HIP lowering.
+  auto T = getToolChain().getTriple();
+
+  if (T.getOS() == llvm::Triple::ChipStar) {
+    // chipStar: run HipSpvPasses via opt, then use the in-tree SPIR-V backend
+    // for codegen (replaces the external llvm-spirv translator).
+
+    // Run HipSpvPasses plugin via opt (must run on LLVM IR before
+    // the SPIR-V backend lowers to MIR).
+    auto PassPluginPath = findPassPlugin(C.getDriver(), Args);
+    if (!PassPluginPath.empty()) {
+      const char *PassPathCStr = C.getArgs().MakeArgString(PassPluginPath);
+      const char *OptOutput = HIP::getTempFile(C, Name + "-lower", "bc");
+      ArgStringList OptArgs{TempFile,     "-load-pass-plugin",
+                            PassPathCStr, "-passes=hip-post-link-passes",
+                            "-o",         OptOutput};
+      const char *Opt =
+          Args.MakeArgString(getToolChain().GetProgramPath("opt"));
+      C.addCommand(std::make_unique<Command>(JA, *this,
+                                             ResponseFileSupport::None(), Opt,
+                                             OptArgs, Inputs, Output));
+      TempFile = OptOutput;
+    }
 
-  // Run LLVM IR passes to lower/expand/emulate HIP code that does not translate
-  // to SPIR-V (E.g. dynamic shared memory).
+    // Compile processed bitcode to SPIR-V using the in-tree backend.
+    ArgStringList ClangArgs;
+    ClangArgs.push_back("--no-default-config");
+    ClangArgs.push_back("-c");
+    ClangArgs.push_back(C.getArgs().MakeArgString("--target=" + T.getTriple()));
+
+    ClangArgs.push_back("-mllvm");
+    ClangArgs.push_back("-spirv-ext=+SPV_INTEL_function_pointers"
+                        ",+SPV_INTEL_subgroups"
+                        ",+SPV_EXT_relaxed_printf_string_address_space"
+                        ",+SPV_KHR_bit_instructions"
+                        ",+SPV_EXT_shader_atomic_float_add");
+
+    ClangArgs.push_back(TempFile);
+    ClangArgs.push_back("-o");
+    ClangArgs.push_back(Output.getFilename());
+
+    const char *Clang =
+        C.getArgs().MakeArgString(C.getDriver().getClangProgramPath());
----------------
linehill wrote:

Using clang driver for emitting SPIR-V (through SPIR-V BE) seems hazarous - it think it's better to [use cc1 like HIPAMD does](https://github.com/llvm/llvm-project/blob/8341e62c6697ab0bbcaf546eba28d5845577f6ee/clang/lib/Driver/ToolChains/HIPAMD.cpp#L171-L187).

https://github.com/llvm/llvm-project/pull/186972