Introduce support of the LLVM SPIR-V Backend to translate LLVM IR to SPIR-V (#3229)

This PR is to introduce support of the LLVM SPIR-V Backend to translate
LLVM IR to SPIR-V. The backend will be preferred over Khronos Translator
only when both conditions are satisfied:
* the SPIR-V Backend is present in the deployment of LLVM,
* there is an environmental variable `TRITON_USE_SPIRV_BACKEND` present
and set to a non-zero integer value.

Khronos Translator remains the default tool to translate LLVM IR to
SPIR-V.

Author: VyacheslavLevytskyy

scripts/compile-triton.sh

@@ -138,7 +138,7 @@ build_llvm() {
     -DCMAKE_BUILD_TYPE=Release \
     -DLLVM_ENABLE_ASSERTIONS=true \
     -DLLVM_ENABLE_PROJECTS="mlir" \
-    -DLLVM_TARGETS_TO_BUILD="X86;NVPTX;AMDGPU" \
+    -DLLVM_TARGETS_TO_BUILD="X86;NVPTX;AMDGPU;SPIRV" \
     -DLLVM_INSTALL_UTILS=true \
     -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
     -DCMAKE_INSTALL_PREFIX=$PACKAGES_DIR/llvm \

third_party/intel/lib/Target/SPIRV/CMakeLists.txt

@@ -1,17 +1,38 @@
 # SPIRV-LLVM-Translator is required.
 find_package(SPIRVToLLVMTranslator)
 
-add_mlir_translation_library(TritonSPIRV
-        SPIRVTranslation.cpp
+# Check if there is the LLVM SPIR-V backend.
+is_llvm_target_library("SPIRV" spirv_present_result INCLUDED_TARGETS)
 
-        LINK_COMPONENTS
-        Core
+if(spirv_present_result)
+  message(STATUS "Found SPIR-V Backend")
+  add_compile_definitions(LLVM_SPIRV_BACKEND_TARGET_PRESENT)
+  add_mlir_translation_library(TritonSPIRV
+    SPIRVTranslation.cpp
 
-        LINK_LIBS PUBLIC
-        TritonLLVMIR
-        # spirv tools
-        LLVMSPIRVLib
-        )
+    LINK_COMPONENTS
+    Core
+    # spirv backend
+    SPIRVCodeGen
+
+    LINK_LIBS PUBLIC
+    TritonLLVMIR
+    # spirv tools
+    LLVMSPIRVLib
+  )
+else()
+  add_mlir_translation_library(TritonSPIRV
+    SPIRVTranslation.cpp
+
+    LINK_COMPONENTS
+    Core
+
+    LINK_LIBS PUBLIC
+    TritonLLVMIR
+    # spirv tools
+    LLVMSPIRVLib
+  )
+endif()
 
 # Add SPIRV-LLVM-Translator include directory.
 target_include_directories(TritonSPIRV PRIVATE ${SPIRVToLLVMTranslator_INCLUDE_DIR})

third_party/intel/lib/Target/SPIRV/SPIRVTranslation.cpp

@@ -11,6 +11,85 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/TargetParser/Triple.h"
+
+#if defined(LLVM_SPIRV_BACKEND_TARGET_PRESENT)
+namespace llvm {
+
+using namespace llvm;
+using namespace SPIRV;
+
+// The LLVM SPIR-V backend exposes an API call that translates LLVM module to
+// SPIR-V and writes results into a string as binary SPIR-V output, providing
+// diagnostics on fail and means of configuring translation.
+extern "C" bool SPIRVTranslate(Module *M, std::string &SpirvObj,
+                               std::string &ErrMsg,
+                               const std::vector<std::string> &AllowExtNames,
+                               llvm::CodeGenOptLevel OLevel,
+                               Triple TargetTriple);
+
+static inline Triple::SubArchType
+spirvVersionToSubArch(SPIRV::VersionNumber VN) {
+  switch (VN) {
+  case SPIRV::VersionNumber::SPIRV_1_0:
+    return Triple::SPIRVSubArch_v10;
+  case VersionNumber::SPIRV_1_1:
+    return Triple::SPIRVSubArch_v11;
+  case VersionNumber::SPIRV_1_2:
+    return Triple::SPIRVSubArch_v12;
+  case VersionNumber::SPIRV_1_3:
+    return Triple::SPIRVSubArch_v13;
+  case VersionNumber::SPIRV_1_4:
+    return Triple::SPIRVSubArch_v14;
+  case VersionNumber::SPIRV_1_5:
+    return Triple::SPIRVSubArch_v15;
+  case VersionNumber::SPIRV_1_6:
+    return Triple::SPIRVSubArch_v16;
+  }
+  return Triple::NoSubArch;
+}
+
+bool runSpirvBackend(Module *M, std::string &Result, std::string &ErrMsg,
+                     const SPIRV::TranslatorOpts &TranslatorOpts) {
+  static const std::string DefaultTriple = "spirv64v1.6-unknown-unknown";
+  static const std::vector<std::string> AllowExtNames{"all"};
+
+  // Correct the Triple value if needed
+  Triple TargetTriple(M->getTargetTriple());
+  if (TargetTriple.isSPIR()) {
+    TargetTriple.setArch(TargetTriple.getArch() == Triple::spir64
+                             ? Triple::spirv64
+                             : Triple::spirv32,
+                         TargetTriple.getSubArch());
+    M->setTargetTriple(TargetTriple.str());
+    // We need to reset Data Layout to conform with the TargetMachine
+    M->setDataLayout("");
+  }
+  if (TargetTriple.getTriple().empty())
+    TargetTriple.setTriple(DefaultTriple);
+  if (TranslatorOpts.getMaxVersion() != VersionNumber::MaximumVersion) {
+    TargetTriple.setArch(TargetTriple.getArch(),
+                         spirvVersionToSubArch(TranslatorOpts.getMaxVersion()));
+    M->setTargetTriple(TargetTriple.str());
+  }
+
+  // Translate the Module into SPIR-V
+  return SPIRVTranslate(M, Result, ErrMsg, AllowExtNames,
+                        CodeGenOptLevel::Aggressive, TargetTriple);
+}
+
+bool runSpirvBackend(Module *M, std::ostream &OS, std::string &ErrMsg,
+                     const SPIRV::TranslatorOpts &TranslatorOpts) {
+  std::string Result;
+  bool Status = runSpirvBackend(M, Result, ErrMsg, TranslatorOpts);
+  if (Status)
+    OS << Result;
+  return Status;
+}
+
+} // namespace llvm
+
+#endif // LLVM_SPIRV_BACKEND_TARGET_PRESENT
 
 namespace triton {
 
@@ -63,7 +142,17 @@ std::string translateLLVMIRToSPIRV(llvm::Module &module) {
   SPIRVOpts.setPreserveOCLKernelArgTypeMetadataThroughString(true);
   SPIRVOpts.setPreserveAuxData(false);
   SPIRVOpts.setSPIRVAllowUnknownIntrinsics({"llvm.genx.GenISA."});
+
+#if defined(LLVM_SPIRV_BACKEND_TARGET_PRESENT)
+  int SpvTranslateMode = 0;
+  if (const char *EnvIsBackend = std::getenv("TRITON_USE_SPIRV_BACKEND"))
+    llvm::StringRef(EnvIsBackend).getAsInteger(10, SpvTranslateMode);
+  auto success = SpvTranslateMode
+                     ? llvm::runSpirvBackend(&module, OS, Err, SPIRVOpts)
+                     : llvm::writeSpirv(&module, SPIRVOpts, OS, Err);
+#else
   auto success = llvm::writeSpirv(&module, SPIRVOpts, OS, Err);
+#endif // LLVM_SPIRV_BACKEND_TARGET_PRESENT
 
   if (!success) {
     llvm::errs() << "SPIRVTranslation: SPIRV translation failed with"