Fix global ctor/dtor translation from SPIRV to LLVM IR

Translate global variable if its storage is StorageClassFunction and its
name is either llvm.global_ctors or llvm.global_dtors. Apply appending
linkage to the global variable.
SPV_INTEL_function_pointers extension is required for the translation.

Author: wenju-he

llvm-spirv/lib/SPIRV/SPIRVReader.cpp

@@ -3309,6 +3309,8 @@ bool SPIRVToLLVM::translate() {
     auto BV = BM->getVariable(I);
     if (BV->getStorageClass() != StorageClassFunction)
       transValue(BV, nullptr, nullptr);
+    else
+      transGlobalCtorDtors(BV);
   }
 
   // Compile unit might be needed during translation of debug intrinsics.
@@ -3651,6 +3653,15 @@ bool SPIRVToLLVM::transDecoration(SPIRVValue *BV, Value *V) {
   return true;
 }
 
+void SPIRVToLLVM::transGlobalCtorDtors(SPIRVVariable *BV) {
+  if (BV->getName() != "llvm.global_ctors" &&
+      BV->getName() != "llvm.global_dtors")
+    return;
+
+  Value *V = transValue(BV, nullptr, nullptr);
+  cast<GlobalValue>(V)->setLinkage(GlobalValue::AppendingLinkage);
+}
+
 bool SPIRVToLLVM::transFPContractMetadata() {
   bool ContractOff = false;
   for (unsigned I = 0, E = BM->getNumFunctions(); I != E; ++I) {

llvm-spirv/lib/SPIRV/SPIRVReader.h

@@ -270,6 +270,7 @@ class SPIRVToLLVM {
 
   void transUserSemantic(SPIRV::SPIRVFunction *Fun);
   void transGlobalAnnotations();
+  void transGlobalCtorDtors(SPIRVVariable *BV);
   void transIntelFPGADecorations(SPIRVValue *BV, Value *V);
 }; // class SPIRVToLLVM
 

llvm-spirv/test/transcoding/SPV_INTEL_function_pointers/global_ctor_dtor.ll

@@ -0,0 +1,74 @@
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc --spirv-ext=+SPV_INTEL_function_pointers -spirv-text -o - | FileCheck %s
+; RUN: llvm-spirv %t.bc --spirv-ext=+SPV_INTEL_function_pointers -o %t.spv
+; RUN: llvm-spirv -r %t.spv
+
+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-unknown"
+
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_test.cpp.ctor, i8* null }]
+@llvm.global_dtors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_test.cpp.dtor, i8* null }]
+@_ZL15DIVERGENCE = internal addrspace(1) global i32 0, align 4
+
+; CHECK: Name [[NameCtor:[0-9]+]] "_GLOBAL__sub_I_test.cpp.ctor"
+; CHECK: Name [[Name1:[0-9]+]] "llvm.global_ctors"
+; CHECK: Name [[NameDtor:[0-9]+]] "_GLOBAL__sub_I_test.cpp.dtor"
+; CHECK: Name [[Name2:[0-9]+]] "llvm.global_dtors"
+; CHECK: Name [[NameInit:[0-9]+]] "__cxx_global_var_init"
+
+; CHECK: LinkageAttributes "llvm.global_ctors" Export
+; CHECK: LinkageAttributes "llvm.global_dtors" Export
+
+; CHECK: TypeFunction {{[0-9]+}} [[TF:[0-9]+]]
+
+; CHECK: TypePointer [[TP:[0-9]+]]
+; CHECK: ConstFunctionPointerINTEL [[TP]] [[FPCtor:[0-9]+]] [[NameCtor]]
+; CHECK: ConstantComposite {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} [[FPCtor]]
+; CHECK: ConstFunctionPointerINTEL [[TP]] [[FPDtor:[0-9]+]] [[NameDtor]]
+; CHECK: ConstantComposite {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} [[FPDtor]]
+
+; CHECK: 5 Function [[TF]] [[NameCtor]] 0
+; CHECK-EMPTY:
+; CHECK-NEXT: Label {{[0-9]+}}
+; CHECK-NEXT: FunctionCall {{[0-9]+}} {{[0-9]+}} [[NameInit]]
+; CHECK-NEXT: Return
+; CHECK-EMPTY:
+; CHECK-NEXT: FunctionEnd
+
+; Function Attrs: nounwind sspstrong
+define internal void @_GLOBAL__sub_I_test.cpp.ctor() #0 {
+  call void @__cxx_global_var_init()
+  ret void
+}
+
+; Function Attrs: nounwind sspstrong
+define internal void @__cxx_global_var_init() #0 {
+  store i32 0, i32 addrspace(4)* addrspacecast (i32 addrspace(1)* @_ZL15DIVERGENCE to i32 addrspace(4)*), align 4
+  ret void
+}
+
+; CHECK: 5 Function [[TF]] [[NameDtor]] 0
+; CHECK-EMPTY:
+; CHECK-NEXT: Label {{[0-9]+}}
+; CHECK-NEXT: Return
+; CHECK-EMPTY:
+; CHECK-NEXT: FunctionEnd
+
+; Function Attrs: nounwind sspstrong
+define internal void @_GLOBAL__sub_I_test.cpp.dtor() #0 {
+  ret void
+}
+
+; Ctor/dtor functions should not be serialized twice.
+; CHECK-NOT: 5 Function [[TF]] [[NameCtor]] 0
+; CHECK-NOT: 5 Function [[TF]] [[NameDtor]] 0
+
+attributes #0 = { nounwind sspstrong "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" }
+
+!opencl.spir.version = !{!0}
+!opencl.used.extensions = !{!1}
+!opencl.used.optional.core.features = !{!1}
+!opencl.compiler.options = !{!1}
+
+!0 = !{i32 1, i32 2}
+!1 = !{}