add support for the SPV_KHR_linkonce_odr extension (#81512)

This PR adds support for the SPV_KHR_linkonce_odr extension and modifies
existing negative test with a positive check for the extension and
proper linkage type in case when the extension is enabled.

SPV_KHR_linkonce_odr adds a "LinkOnceODR" linkage type, allowing proper
translation of, for example, C++ templates classes merging during
linking from different modules and supporting any other cases when a
global variable/function must be merged with equivalent global
variable(s)/function(s) from other modules during the linking process.

Author: VyacheslavLevytskyy

llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp

@@ -332,6 +332,10 @@ bool SPIRVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   if (F.hasName())
     buildOpName(FuncVReg, F.getName(), MIRBuilder);
 
+  // Get access to information about available extensions
+  const auto *ST =
+      static_cast<const SPIRVSubtarget *>(&MIRBuilder.getMF().getSubtarget());
+
   // Handle entry points and function linkage.
   if (isEntryPoint(F)) {
     const auto &STI = MIRBuilder.getMF().getSubtarget<SPIRVSubtarget>();
@@ -342,15 +346,19 @@ bool SPIRVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
     addStringImm(F.getName(), MIB);
   } else if (F.getLinkage() == GlobalValue::LinkageTypes::ExternalLinkage ||
              F.getLinkage() == GlobalValue::LinkOnceODRLinkage) {
-    auto LnkTy = F.isDeclaration() ? SPIRV::LinkageType::Import
-                                   : SPIRV::LinkageType::Export;
+    SPIRV::LinkageType::LinkageType LnkTy =
+        F.isDeclaration()
+            ? SPIRV::LinkageType::Import
+            : (F.getLinkage() == GlobalValue::LinkOnceODRLinkage &&
+                       ST->canUseExtension(
+                           SPIRV::Extension::SPV_KHR_linkonce_odr)
+                   ? SPIRV::LinkageType::LinkOnceODR
+                   : SPIRV::LinkageType::Export);
     buildOpDecorate(FuncVReg, MIRBuilder, SPIRV::Decoration::LinkageAttributes,
                     {static_cast<uint32_t>(LnkTy)}, F.getGlobalIdentifier());
   }
 
   // Handle function pointers decoration
-  const auto *ST =
-      static_cast<const SPIRVSubtarget *>(&MIRBuilder.getMF().getSubtarget());
   bool hasFunctionPointers =
       ST->canUseExtension(SPIRV::Extension::SPV_INTEL_function_pointers);
   if (hasFunctionPointers) {
@@ -393,7 +401,7 @@ void SPIRVCallLowering::produceIndirectPtrTypes(
     // SPIR-V pointer to function type:
     SPIRVType *IndirectFuncPtrTy = GR->getOrCreateSPIRVPointerType(
         SpirvFuncTy, MIRBuilder, SPIRV::StorageClass::Function);
-    // Correct the Calee type
+    // Correct the Callee type
     GR->assignSPIRVTypeToVReg(IndirectFuncPtrTy, IC.Callee, MF);
   }
 }

llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp

@@ -1601,7 +1601,10 @@ bool SPIRVInstructionSelector::selectGlobalValue(
   SPIRV::LinkageType::LinkageType LnkType =
       (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
           ? SPIRV::LinkageType::Import
-          : SPIRV::LinkageType::Export;
+          : (GV->getLinkage() == GlobalValue::LinkOnceODRLinkage &&
+                     STI.canUseExtension(SPIRV::Extension::SPV_KHR_linkonce_odr)
+                 ? SPIRV::LinkageType::LinkOnceODR
+                 : SPIRV::LinkageType::Export);
 
   Register Reg = GR.buildGlobalVariable(ResVReg, ResType, GlobalIdent, GV,
                                         Storage, Init, GlobalVar->isConstant(),

llvm/lib/Target/SPIRV/SPIRVModuleAnalysis.cpp

@@ -679,6 +679,12 @@ static void addOpDecorateReqs(const MachineInstr &MI, unsigned DecIndex,
     auto BuiltIn = static_cast<SPIRV::BuiltIn::BuiltIn>(BuiltInOp);
     Reqs.addRequirements(getSymbolicOperandRequirements(
         SPIRV::OperandCategory::BuiltInOperand, BuiltIn, ST, Reqs));
+  } else if (Dec == SPIRV::Decoration::LinkageAttributes) {
+    int64_t LinkageOp = MI.getOperand(MI.getNumOperands() - 1).getImm();
+    SPIRV::LinkageType::LinkageType LnkType =
+        static_cast<SPIRV::LinkageType::LinkageType>(LinkageOp);
+    if (LnkType == SPIRV::LinkageType::LinkOnceODR)
+      Reqs.addExtension(SPIRV::Extension::SPV_KHR_linkonce_odr);
   }
 }
 

llvm/lib/Target/SPIRV/SPIRVSubtarget.cpp

@@ -54,6 +54,11 @@ cl::list<SPIRV::Extension::Extension> Extensions(
                    "SPV_KHR_bit_instructions",
                    "This enables bit instructions to be used by SPIR-V modules "
                    "without requiring the Shader capability"),
+        clEnumValN(
+            SPIRV::Extension::SPV_KHR_linkonce_odr, "SPV_KHR_linkonce_odr",
+            "Allows to use the LinkOnceODR linkage type that is to let "
+            "a function or global variable to be merged with other functions "
+            "or global variables of the same name when linkage occurs."),
         clEnumValN(SPIRV::Extension::SPV_INTEL_function_pointers,
                    "SPV_INTEL_function_pointers",
                    "Allows translation of function pointers")));

llvm/lib/Target/SPIRV/SPIRVSymbolicOperands.td

@@ -1040,6 +1040,7 @@ multiclass LinkageTypeOperand<bits<32> value, list<Capability> reqCapabilities>
 
 defm Export : LinkageTypeOperand<0, [Linkage]>;
 defm Import : LinkageTypeOperand<1, [Linkage]>;
+defm LinkOnceODR : LinkageTypeOperand<2, [Linkage]>;
 
 //===----------------------------------------------------------------------===//
 // Multiclass used to define AccessQualifier enum values and at the same time

llvm/test/CodeGen/SPIRV/LinkOnceODR.ll

@@ -1,5 +1,14 @@
-;; No extension -> no LinkOnceODR
+; RUN: llc -O0 -mtriple=spirv32-unknown-unknown --spirv-extensions=SPV_KHR_linkonce_odr %s -o - | FileCheck %s --check-prefix=CHECK-SPIRV-EXT
+; TODO: %if spirv-tools %{ llc -O0 -mtriple=spirv32-unknown-unknown --spirv-extensions=SPV_KHR_linkonce_odr %s -o - -filetype=obj | spirv-val %}
+
+; CHECK-SPIRV-EXT: Capability Linkage
+; CHECK-SPIRV-EXT: Extension "SPV_KHR_linkonce_odr"
+; CHECK-SPIRV-EXT-DAG: OpDecorate %[[#]] LinkageAttributes "GV" LinkOnceODR
+; CHECK-SPIRV-EXT-DAG: OpDecorate %[[#]] LinkageAttributes "square" LinkOnceODR
+
+; No extension -> no LinkOnceODR
 ; RUN: llc -O0 -mtriple=spirv32-unknown-unknown %s -o - | FileCheck %s --check-prefix=CHECK-SPIRV
+; TODO: %if spirv-tools %{ llc -O0 -mtriple=spirv32-unknown-unknown %s -o - -filetype=obj | spirv-val %}
 
 ; CHECK-SPIRV-NOT: OpExtension "SPV_KHR_linkonce_odr"
 ; CHECK-SPIRV-NOT: OpDecorate %[[#]] LinkageAttributes "GV" LinkOnceODR 

llvm/test/CodeGen/SPIRV/LinkOnceODRFun.ll

@@ -0,0 +1,17 @@
+; RUN: llc -O0 -mtriple=spirv32-unknown-unknown --spirv-extensions=SPV_KHR_linkonce_odr %s -o - | FileCheck %s --check-prefix=CHECK-SPIRV-EXT
+; TODO: %if spirv-tools %{ llc -O0 -mtriple=spirv32-unknown-unknown --spirv-extensions=SPV_KHR_linkonce_odr %s -o - -filetype=obj | spirv-val %}
+
+; CHECK-SPIRV-EXT: Capability Linkage
+; CHECK-SPIRV-EXT: Extension "SPV_KHR_linkonce_odr"
+; CHECK-SPIRV-EXT-DAG: OpDecorate %[[#]] LinkageAttributes "square" LinkOnceODR
+
+define spir_kernel void @k() {
+entry:
+  %call = call spir_func i32 @square(i32 2)
+  ret void
+}
+
+define linkonce_odr dso_local spir_func i32 @square(i32 %in) {
+entry:
+  ret i32 %in
+}