Add ability to preserve all function metadata and attributes from LLVM-IR

Initial implementation of function metadata and attribute preservation

In Intel's SYCL compiler, we have a use case where we need to convert to SPIR-V and then back to LLVM-IR and preserve all function metadata and attributes. The metadata and attributes we need to preserve have no value outside an internal stage of Intel's SYCL compiler and are not good fits for SPIR-V extensions. The list of what is needed is very volatile as well.

To implement generic support in the translator, the general approach is to use SPV_KHR_non_semantic_info to add a new nonsemantic EIS, named NonSemantic.AuxData

This new instruction set has two instructions:
NonSemanticAuxDataFunctionMetadata
and
NonSemanticAuxDataFunctionAttribute

Both instructions will be placed outside of the function CFG and take in what function to target as an operand, similar to debuginfo. We do this to support function declarations.

The operands after the function to target are either strings or values describing the metadata or attribute. Specific information can be found in the SPIRVWriter.cpp changes.

I also added a new option, --spirv-preserve-auxdata to preserve these.

If a flag is passed for translation to SPIR-V the respective information will be preserved as described above. The flag is also required for reverse translation. If it not provided, it will be dropped as allowed in the spec.

In order to handle the case of some metadata/attributes being handled manually (maybe we have metadata "foo=bar" in LLVM-IR, but we translate to "foo=oof" for some reason in SPIR-V (and thus reverse translation)), we process these new instructions very late in reverse translation, and if the metadata or attribute already exists, we skip it.

Signed-off-by: Sarnie, Nick <[email protected]>

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@f729c49

Author: sarnex

llvm-spirv/include/LLVMSPIRVOpts.h

@@ -90,7 +90,9 @@ enum class DebugInfoEIS : uint32_t {
 /// \brief Helper class to manage SPIR-V translation
 class TranslatorOpts {
 public:
-  using ExtensionsStatusMap = std::map<ExtensionID, bool>;
+  // Unset optional means not directly specified by user
+  using ExtensionsStatusMap = std::map<ExtensionID, std::optional<bool>>;
+
   using ArgList = llvm::SmallVector<llvm::StringRef, 4>;
 
   TranslatorOpts() = default;
@@ -107,11 +109,14 @@ class TranslatorOpts {
     if (ExtStatusMap.end() == I)
       return false;
 
-    return I->second;
+    return I->second && *I->second;
   }
 
   void setAllowedToUseExtension(ExtensionID Extension, bool Allow = true) {
-    ExtStatusMap[Extension] = Allow;
+    // Only allow using the extension if it has not already been disabled
+    auto I = ExtStatusMap.find(Extension);
+    if (I == ExtStatusMap.end() || !I->second || (*I->second) == true)
+      ExtStatusMap[Extension] = Allow;
   }
 
   VersionNumber getMaxVersion() const { return MaxVersion; }
@@ -122,6 +127,10 @@ class TranslatorOpts {
 
   void setMemToRegEnabled(bool Mem2Reg) { SPIRVMemToReg = Mem2Reg; }
 
+  bool preserveAuxData() const { return PreserveAuxData; }
+
+  void setPreserveAuxData(bool ArgValue) { PreserveAuxData = ArgValue; }
+
   void setGenKernelArgNameMDEnabled(bool ArgNameMD) {
     GenKernelArgNameMD = ArgNameMD;
   }
@@ -230,6 +239,8 @@ class TranslatorOpts {
   // Add a workaround to preserve OpenCL kernel_arg_type and
   // kernel_arg_type_qual metadata through OpString
   bool PreserveOCLKernelArgTypeMetadataThroughString = false;
+
+  bool PreserveAuxData = false;
 };
 
 } // namespace SPIRV

llvm-spirv/lib/SPIRV/SPIRVReader.cpp

@@ -3358,6 +3358,11 @@ bool SPIRVToLLVM::translate() {
 
   DbgTran->addDbgInfoVersion();
   DbgTran->finalize();
+
+  for (SPIRVExtInst *EI : BM->getAuxDataInstVec()) {
+    transAuxDataInst(EI);
+  }
+
   return true;
 }
 
@@ -4500,6 +4505,60 @@ Instruction *SPIRVToLLVM::transOCLBuiltinFromExtInst(SPIRVExtInst *BC,
   return CI;
 }
 
+void SPIRVToLLVM::transAuxDataInst(SPIRVExtInst *BC) {
+  assert(BC->getExtSetKind() == SPIRV::SPIRVEIS_NonSemantic_AuxData);
+  if (!BC->getModule()->preserveAuxData())
+    return;
+  auto Args = BC->getArguments();
+  // Args 0 and 1 are common between attributes and metadata.
+  // 0 is the function, 1 is the name of the attribute/metadata as a string
+  auto *SpvFcn = BC->getModule()->getValue(Args[0]);
+  auto *F = static_cast<Function *>(getTranslatedValue(SpvFcn));
+  assert(F && "Function should already have been translated!");
+  auto AttrOrMDName = BC->getModule()->get<SPIRVString>(Args[1])->getStr();
+  switch (BC->getExtOp()) {
+  case NonSemanticAuxData::FunctionAttribute: {
+    assert(Args.size() < 4 && "Unexpected FunctionAttribute Args");
+    // If this attr was specially handled and added elsewhere, skip it.
+    if (F->hasFnAttribute(AttrOrMDName))
+      return;
+    // For attributes, arg 2 is the attribute value as a string, which may not
+    // exist.
+    if (Args.size() == 3) {
+      auto AttrValue = BC->getModule()->get<SPIRVString>(Args[2])->getStr();
+      F->addFnAttr(AttrOrMDName, AttrValue);
+    } else {
+      F->addFnAttr(AttrOrMDName);
+    }
+    break;
+  }
+  case NonSemanticAuxData::FunctionMetadata: {
+    // If this metadata was specially handled and added elsewhere, skip it.
+    if (F->hasMetadata(AttrOrMDName))
+      return;
+    SmallVector<Metadata *> MetadataArgs;
+    // Process the metadata values.
+    for (size_t CurArg = 2; CurArg < Args.size(); CurArg++) {
+      auto *Arg = BC->getModule()->get<SPIRVEntry>(Args[CurArg]);
+      // For metadata, the metadata values can be either values or strings.
+      if (Arg->getOpCode() == OpString) {
+        auto *ArgAsStr = static_cast<SPIRVString *>(Arg);
+        MetadataArgs.push_back(
+            MDString::get(F->getContext(), ArgAsStr->getStr()));
+      } else {
+        auto *ArgAsVal = static_cast<SPIRVValue *>(Arg);
+        auto *TranslatedMD = transValue(ArgAsVal, F, nullptr);
+        MetadataArgs.push_back(ValueAsMetadata::get(TranslatedMD));
+      }
+    }
+    F->setMetadata(AttrOrMDName, MDNode::get(*Context, MetadataArgs));
+    break;
+  }
+  default:
+    llvm_unreachable("Invalid op");
+  }
+}
+
 // SPIR-V only contains language version. Use OpenCL language version as
 // SPIR version.
 void SPIRVToLLVM::transSourceLanguage() {

llvm-spirv/lib/SPIRV/SPIRVReader.h

@@ -100,6 +100,7 @@ class SPIRVToLLVM : private BuiltinCallHelper {
   bool transDecoration(SPIRVValue *, Value *);
   bool transAlign(SPIRVValue *, Value *);
   Instruction *transOCLBuiltinFromExtInst(SPIRVExtInst *BC, BasicBlock *BB);
+  void transAuxDataInst(SPIRVExtInst *BC);
   std::vector<Value *> transValue(const std::vector<SPIRVValue *> &,
                                   Function *F, BasicBlock *);
   Function *transFunction(SPIRVFunction *F);

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -970,6 +970,8 @@ SPIRVFunction *LLVMToSPIRVBase::transFunctionDecl(Function *F) {
 
   transFunctionMetadataAsUserSemanticDecoration(BF, F);
 
+  transAuxDataInst(BF, F);
+
   SPIRVDBG(dbgs() << "[transFunction] " << *F << " => ";
            spvdbgs() << *BF << '\n';)
   return BF;
@@ -1137,6 +1139,72 @@ void LLVMToSPIRVBase::transFunctionMetadataAsUserSemanticDecoration(
   }
 }
 
+void LLVMToSPIRVBase::transAuxDataInst(SPIRVFunction *BF, Function *F) {
+  auto *BM = BF->getModule();
+  if (!BM->preserveAuxData())
+    return;
+  BM->addExtension(SPIRV::ExtensionID::SPV_KHR_non_semantic_info);
+  const auto &FnAttrs = F->getAttributes().getFnAttrs();
+  for (const auto &Attr : FnAttrs) {
+    std::vector<SPIRVWord> Ops;
+    Ops.push_back(BF->getId());
+    if (Attr.isStringAttribute()) {
+      // Format for String attributes is:
+      // NonSemanticAuxDataFunctionAttribute Fcn AttrName AttrValue
+      // or, if no value:
+      // NonSemanticAuxDataFunctionAttribute Fcn AttrName
+      //
+      // AttrName and AttrValue are always Strings
+      StringRef AttrKind = Attr.getKindAsString();
+      StringRef AttrValue = Attr.getValueAsString();
+      auto *KindSpvString = BM->getString(AttrKind.str());
+      Ops.push_back(KindSpvString->getId());
+      if (!AttrValue.empty()) {
+        auto *ValueSpvString = BM->getString(AttrValue.str());
+        Ops.push_back(ValueSpvString->getId());
+      }
+    } else {
+      // Format for other types is:
+      // NonSemanticAuxDataFunctionAttribute Fcn AttrStr
+      // AttrStr is always a String.
+      std::string AttrStr = Attr.getAsString();
+      auto *AttrSpvString = BM->getString(AttrStr);
+      Ops.push_back(AttrSpvString->getId());
+    }
+    BM->addAuxData(NonSemanticAuxData::FunctionAttribute,
+                   transType(Type::getVoidTy(F->getContext())), Ops);
+  }
+  SmallVector<std::pair<unsigned, MDNode *>> AllMD;
+  SmallVector<StringRef> MDNames;
+  F->getContext().getMDKindNames(MDNames);
+  F->getAllMetadata(AllMD);
+  for (auto MD : AllMD) {
+    // Format for metadata is:
+    // NonSemanticAuxDataFunctionMetadata Fcn MDName MDVals...
+    // MDName is always a String, MDVals have different types as explained
+    // below. Also note this instruction has a variable number of operands
+    std::vector<SPIRVWord> Ops;
+    Ops.push_back(BF->getId());
+    Ops.push_back(BM->getString(MDNames[MD.first].str())->getId());
+    for (unsigned int OpIdx = 0; OpIdx < MD.second->getNumOperands(); OpIdx++) {
+      const auto &CurOp = MD.second->getOperand(OpIdx);
+      if (auto *MDStr = dyn_cast<MDString>(CurOp)) {
+        // For MDString, MDVal is String
+        auto *SPIRVStr = BM->getString(MDStr->getString().str());
+        Ops.push_back(SPIRVStr->getId());
+      } else if (auto *ValueAsMeta = dyn_cast<ValueAsMetadata>(CurOp)) {
+        // For Value metadata, MDVal is a SPIRVValue
+        auto *SPIRVVal = transValue(ValueAsMeta->getValue(), nullptr);
+        Ops.push_back(SPIRVVal->getId());
+      } else {
+        assert(false && "Unsupported metadata type");
+      }
+    }
+    BM->addAuxData(NonSemanticAuxData::FunctionMetadata,
+                   transType(Type::getVoidTy(F->getContext())), Ops);
+  }
+}
+
 SPIRVValue *LLVMToSPIRVBase::transConstantUse(Constant *C) {
   // Constant expressions expect their pointer types to be i8* in opaque pointer
   // mode, but the value may have a different "natural" type. If that is the
@@ -2828,6 +2896,11 @@ bool LLVMToSPIRVBase::transBuiltinSet() {
             SPIRVBuiltinSetNameMap::map(BM->getDebugInfoEIS()), &EISId))
       return false;
   }
+  if (BM->preserveAuxData()) {
+    if (!BM->importBuiltinSet(
+            SPIRVBuiltinSetNameMap::map(SPIRVEIS_NonSemantic_AuxData), &EISId))
+      return false;
+  }
   return true;
 }
 

llvm-spirv/lib/SPIRV/SPIRVWriter.h

@@ -124,6 +124,8 @@ class LLVMToSPIRVBase : protected BuiltinCallHelper {
   void transFPGAFunctionMetadata(SPIRVFunction *BF, Function *F);
   void transFunctionMetadataAsUserSemanticDecoration(SPIRVFunction *BF,
                                                      Function *F);
+  void transAuxDataInst(SPIRVFunction *BF, Function *F);
+
   bool transGlobalVariables();
 
   Op transBoolOpCode(SPIRVValue *Opn, Op OC);

llvm-spirv/lib/SPIRV/libSPIRV/NonSemantic.AuxData.h

@@ -0,0 +1,33 @@
+/*
+** Copyright (c) 2023 The Khronos Group Inc.
+**
+** Permission is hereby granted, free of charge, to any person obtaining a copy
+** of this software and/or associated documentation files (the "Materials"),
+** to deal in the Materials without restriction, including without limitation
+** the rights to use, copy, modify, merge, publish, distribute, sublicense,
+** and/or sell copies of the Materials, and to permit persons to whom the
+** Materials are furnished to do so, subject to the following conditions:
+**
+** The above copyright notice and this permission notice shall be included in
+** all copies or substantial portions of the Materials.
+**
+** MODIFICATIONS TO THIS FILE MAY MEAN IT NO LONGER ACCURATELY REFLECTS KHRONOS
+** STANDARDS. THE UNMODIFIED, NORMATIVE VERSIONS OF KHRONOS SPECIFICATIONS AND
+** HEADER INFORMATION ARE LOCATED AT https://www.khronos.org/registry/
+**
+** THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+** OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+** FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+** THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+** LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+** FROM,OUT OF OR IN CONNECTION WITH THE MATERIALS OR THE USE OR OTHER DEALINGS
+** IN THE MATERIALS.
+*/
+
+namespace NonSemanticAuxData {
+enum Instruction {
+  FunctionMetadata = 0,
+  FunctionAttribute = 1,
+  PreserveCount = 2
+};
+} // namespace NonSemanticAuxData

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVEnum.h

@@ -80,6 +80,7 @@ enum SPIRVExtInstSetKind {
   SPIRVEIS_OpenCL_DebugInfo_100,
   SPIRVEIS_NonSemantic_Shader_DebugInfo_100,
   SPIRVEIS_NonSemantic_Shader_DebugInfo_200,
+  SPIRVEIS_NonSemantic_AuxData,
   SPIRVEIS_Count,
 };
 
@@ -135,6 +136,7 @@ template <> inline void SPIRVMap<SPIRVExtInstSetKind, std::string>::init() {
       "NonSemantic.Shader.DebugInfo.100");
   add(SPIRVEIS_NonSemantic_Shader_DebugInfo_200,
       "NonSemantic.Shader.DebugInfo.200");
+  add(SPIRVEIS_NonSemantic_AuxData, "NonSemantic.AuxData");
 }
 typedef SPIRVMap<SPIRVExtInstSetKind, std::string> SPIRVBuiltinSetNameMap;
 

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVExtInst.h

@@ -40,6 +40,7 @@
 #ifndef SPIRV_LIBSPIRV_SPIRVEXTINST_H
 #define SPIRV_LIBSPIRV_SPIRVEXTINST_H
 
+#include "NonSemantic.AuxData.h"
 #include "OpenCL.std.h"
 #include "SPIRV.debug.h"
 #include "SPIRVEnum.h"
@@ -263,6 +264,16 @@ template <> inline void SPIRVMap<SPIRVDebugExtOpKind, std::string>::init() {
 }
 SPIRV_DEF_NAMEMAP(SPIRVDebugExtOpKind, SPIRVDebugExtOpMap)
 
+typedef NonSemanticAuxData::Instruction NonSemanticAuxDataOpKind;
+template <>
+inline void SPIRVMap<NonSemanticAuxDataOpKind, std::string>::init() {
+  add(NonSemanticAuxData::FunctionMetadata,
+      "NonSemanticAuxDataFunctionMetadata");
+  add(NonSemanticAuxData::FunctionAttribute,
+      "NonSemanticAuxDataFunctionAttribute");
+}
+SPIRV_DEF_NAMEMAP(NonSemanticAuxDataOpKind, NonSemanticAuxDataOpMap)
+
 } // namespace SPIRV
 
 #endif // SPIRV_LIBSPIRV_SPIRVEXTINST_H

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVInstruction.h

@@ -42,6 +42,7 @@
 
 #include "SPIRVBasicBlock.h"
 #include "SPIRVEnum.h"
+#include "SPIRVFunction.h"
 #include "SPIRVIsValidEnum.h"
 #include "SPIRVOpCode.h"
 #include "SPIRVStream.h"
@@ -1763,7 +1764,8 @@ class SPIRVExtInst : public SPIRVFunctionCallGeneric<OpExtInst, 5> {
     assert((ExtSetKind == SPIRVEIS_OpenCL || ExtSetKind == SPIRVEIS_Debug ||
             ExtSetKind == SPIRVEIS_OpenCL_DebugInfo_100 ||
             ExtSetKind == SPIRVEIS_NonSemantic_Shader_DebugInfo_100 ||
-            ExtSetKind == SPIRVEIS_NonSemantic_Shader_DebugInfo_200) &&
+            ExtSetKind == SPIRVEIS_NonSemantic_Shader_DebugInfo_200 ||
+            ExtSetKind == SPIRVEIS_NonSemantic_AuxData) &&
            "not supported");
   }
   void encode(spv_ostream &O) const override {
@@ -1778,6 +1780,9 @@ class SPIRVExtInst : public SPIRVFunctionCallGeneric<OpExtInst, 5> {
     case SPIRVEIS_NonSemantic_Shader_DebugInfo_200:
       getEncoder(O) << ExtOpDebug;
       break;
+    case SPIRVEIS_NonSemantic_AuxData:
+      getEncoder(O) << ExtOpNonSemanticAuxData;
+      break;
     default:
       assert(0 && "not supported");
       getEncoder(O) << ExtOp;
@@ -1797,6 +1802,9 @@ class SPIRVExtInst : public SPIRVFunctionCallGeneric<OpExtInst, 5> {
     case SPIRVEIS_NonSemantic_Shader_DebugInfo_200:
       getDecoder(I) >> ExtOpDebug;
       break;
+    case SPIRVEIS_NonSemantic_AuxData:
+      getDecoder(I) >> ExtOpNonSemanticAuxData;
+      break;
     default:
       assert(0 && "not supported");
       getDecoder(I) >> ExtOp;
@@ -1842,13 +1850,20 @@ class SPIRVExtInst : public SPIRVFunctionCallGeneric<OpExtInst, 5> {
     return ArgTypes;
   }
 
+  std::optional<ExtensionID> getRequiredExtension() const override {
+    if (SPIRVBuiltinSetNameMap::map(ExtSetKind).find("NonSemantic.") == 0)
+      return ExtensionID::SPV_KHR_non_semantic_info;
+    return {};
+  }
+
 protected:
   SPIRVExtInstSetKind ExtSetKind;
   SPIRVId ExtSetId;
   union {
     SPIRVWord ExtOp;
     OCLExtOpKind ExtOpOCL;
     SPIRVDebugExtOpKind ExtOpDebug;
+    NonSemanticAuxDataOpKind ExtOpNonSemanticAuxData;
   };
 };