Support UserSemantic decoration on functions (#666)

Added support of SPIR-V -> LLVM IR translation for UserSemantic
decoration applied to functions. Having that decoration on functions
is against SPIR-V spec, but it is useful for prototyping different features:
you can easily propagate custom annotation string through SPIR-V
to see if your idea works or not without adding new code
to the translator

Signed-off-by: amochalo <anastasiya.mochalova@intel.com>

llvm-spirv/lib/SPIRV/SPIRVReader.cpp

@@ -3244,7 +3244,6 @@ bool SPIRVToLLVM::translate() {
     if (BV->getStorageClass() != StorageClassFunction)
       transValue(BV, nullptr, nullptr);
   }
-  transGlobalAnnotations();
 
   // Compile unit might be needed during translation of debug intrinsics.
   for (SPIRVExtInst *EI : BM->getDebugInstVec()) {
@@ -3263,8 +3262,11 @@ bool SPIRVToLLVM::translate() {
 
   for (unsigned I = 0, E = BM->getNumFunctions(); I != E; ++I) {
     transFunction(BM->getFunction(I));
+    transUserSemantic(BM->getFunction(I));
   }
 
+  transGlobalAnnotations();
+
   if (!transMetadata())
     return false;
   if (!transFPContractMetadata())
@@ -3528,6 +3530,38 @@ void SPIRVToLLVM::transIntelFPGADecorations(SPIRVValue *BV, Value *V) {
   }
 }
 
+// Having UserSemantic decoration on Function is against the spec, but we allow
+// this for various purposes (like prototyping new features when we need to
+// attach some information on function and propagate that through SPIR-V and
+// ect.)
+void SPIRVToLLVM::transUserSemantic(SPIRV::SPIRVFunction *Fun) {
+  auto TransFun = transFunction(Fun);
+  for (auto UsSem : Fun->getDecorationStringLiteral(DecorationUserSemantic)) {
+    auto V = cast<Value>(TransFun);
+    Constant *StrConstant =
+        ConstantDataArray::getString(*Context, StringRef(UsSem));
+    auto *GS = new GlobalVariable(
+        *TransFun->getParent(), StrConstant->getType(),
+        /*IsConstant*/ true, GlobalValue::PrivateLinkage, StrConstant, "");
+
+    GS->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
+    GS->setSection("llvm.metadata");
+
+    Type *ResType = PointerType::getInt8PtrTy(
+        V->getContext(), V->getType()->getPointerAddressSpace());
+    Constant *C =
+        ConstantExpr::getPointerBitCastOrAddrSpaceCast(TransFun, ResType);
+
+    Type *Int8PtrTyPrivate = Type::getInt8PtrTy(*Context, SPIRAS_Private);
+    IntegerType *Int32Ty = Type::getInt32Ty(*Context);
+
+    llvm::Constant *Fields[4] = {
+        C, ConstantExpr::getBitCast(GS, Int8PtrTyPrivate),
+        UndefValue::get(Int8PtrTyPrivate), UndefValue::get(Int32Ty)};
+    GlobalAnnotations.push_back(ConstantStruct::getAnon(Fields));
+  }
+}
+
 void SPIRVToLLVM::transGlobalAnnotations() {
   if (!GlobalAnnotations.empty()) {
     Constant *Array =

llvm-spirv/lib/SPIRV/SPIRVReader.h

@@ -267,6 +267,7 @@ class SPIRVToLLVM {
   Instruction *transOCLAllAny(SPIRVInstruction *BI, BasicBlock *BB);
   Instruction *transOCLRelational(SPIRVInstruction *BI, BasicBlock *BB);
 
+  void transUserSemantic(SPIRV::SPIRVFunction *Fun);
   void transGlobalAnnotations();
   void transIntelFPGADecorations(SPIRVValue *BV, Value *V);
 }; // class SPIRVToLLVM

llvm-spirv/test/transcoding/GlobalFunAnnotate.ll

@@ -0,0 +1,37 @@
+;RUN: llvm-as %s -o %t.bc
+;RUN: llvm-spirv %t.bc -o %t.spv
+;RUN: llvm-spirv %t.spv -to-text -o - | FileCheck %s --check-prefix=CHECK-SPIRV
+;RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+;RUN: llvm-dis %t.rev.bc -o - | FileCheck %s --check-prefix=CHECK-LLVM
+
+;CHECK-SPIRV: Decorate {{[0-9]+}} UserSemantic "annotation_on_function"
+
+;CHECK-LLVM: @0 = private unnamed_addr constant [23 x i8] c"annotation_on_function\00", section "llvm.metadata"
+;CHECK-LLVM: @llvm.global.annotations = appending global [1 x { i8*, i8*, i8*, i32 }] [{ i8*, i8*, i8*, i32 } { i8* bitcast (void ()* @foo to i8*), i8* getelementptr inbounds ([23 x i8], [23 x i8]* @0, i32 0, i32 0), i8* undef, i32 undef }], section "llvm.metadata"
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+target triple = "spir64-unknown-linux-sycldevice"
+
+@.str = private unnamed_addr constant [23 x i8] c"annotation_on_function\00", section "llvm.metadata"
+@.str.1 = private unnamed_addr constant [6 x i8] c"an.cl\00", section "llvm.metadata"
+@llvm.global.annotations = appending global [1 x { i8*, i8*, i8*, i32 }] [{ i8*, i8*, i8*, i32 } { i8* bitcast (void ()* @foo to i8*), i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.1, i32 0, i32 0), i32 2 }], section "llvm.metadata"
+
+; Function Attrs: convergent norecurse nounwind
+define dso_local spir_func void @foo() #0 {
+entry:
+  ret void
+}
+
+attributes #0 = { convergent norecurse nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0}
+!opencl.ocl.version = !{!1}
+!opencl.spir.version = !{!2, !2}
+!spirv.Source = !{!3}
+!llvm.ident = !{!4}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 1, i32 0}
+!2 = !{i32 1, i32 2}
+!3 = !{i32 4, i32 100000}
+!4 = !{!"clang version 12.0.0 (https://github.com/c199914007/llvm.git 074e97d48896b959dfc832e2f1dd806796cde390)"}