[CUDA] Increment VTable index for device thunks

Currently, the clang frontend incorrectly emits
the callee instead of the thunk for the callee
in the VTable. This is the case because the
thunk index is not incremented when their
callees cannot be emitted. This patch fixes
this bug.

Author: gandhi56

clang/lib/CodeGen/CGVTables.cpp

@@ -771,6 +771,10 @@ void CodeGenVTables::addVTableComponent(ConstantArrayBuilder &builder,
   case VTableComponent::CK_DeletingDtorPointer: {
     GlobalDecl GD = component.getGlobalDecl();
 
+    const bool IsThunk =
+        nextVTableThunkIndex < layout.vtable_thunks().size() &&
+        layout.vtable_thunks()[nextVTableThunkIndex].first == componentIndex;
+
     if (CGM.getLangOpts().CUDA) {
       // Emit NULL for methods we can't codegen on this
       // side. Otherwise we'd end up with vtable with unresolved
@@ -782,9 +786,12 @@ void CodeGenVTables::addVTableComponent(ConstantArrayBuilder &builder,
           CGM.getLangOpts().CUDAIsDevice
               ? MD->hasAttr<CUDADeviceAttr>()
               : (MD->hasAttr<CUDAHostAttr>() || !MD->hasAttr<CUDADeviceAttr>());
-      if (!CanEmitMethod)
+      if (!CanEmitMethod) {
+        if (IsThunk)
+          nextVTableThunkIndex++;
         return builder.add(
             llvm::ConstantExpr::getNullValue(CGM.GlobalsInt8PtrTy));
+      }
       // Method is acceptable, continue processing as usual.
     }
 
@@ -830,9 +837,7 @@ void CodeGenVTables::addVTableComponent(ConstantArrayBuilder &builder,
       fnPtr = DeletedVirtualFn;
 
     // Thunks.
-    } else if (nextVTableThunkIndex < layout.vtable_thunks().size() &&
-               layout.vtable_thunks()[nextVTableThunkIndex].first ==
-                   componentIndex) {
+    } else if (IsThunk) {
       auto &thunkInfo = layout.vtable_thunks()[nextVTableThunkIndex].second;
 
       nextVTableThunkIndex++;

clang/test/CodeGenCUDA/increment-index-for-thunks.cu

@@ -3,10 +3,10 @@
 // RUN: %clang_cc1 -fcuda-is-device -triple spirv64-amd-amdhsa \
 // RUN:   -emit-llvm -xhip %s -o - | FileCheck %s --check-prefix=SPIRV
 
-// GCN: @_ZTV1C = linkonce_odr unnamed_addr addrspace(1) constant { [5 x ptr addrspace(1)], [4 x ptr addrspace(1)] } { [5 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1B2f2Ev to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1C2f1Ev to ptr addrspace(1))], [4 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 -8 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1C2f1Ev to ptr addrspace(1))] }, comdat, align 8
+// GCN: @_ZTV1C = linkonce_odr unnamed_addr addrspace(1) constant { [5 x ptr addrspace(1)], [4 x ptr addrspace(1)] } { [5 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1B2f2Ev to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1C2f1Ev to ptr addrspace(1))], [4 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 -8 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZThn8_N1C2f1Ev to ptr addrspace(1))] }, comdat, align 8
 // GCN: @_ZTV1B = linkonce_odr unnamed_addr addrspace(1) constant { [3 x ptr addrspace(1)] } { [3 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @_ZN1B2f2Ev to ptr addrspace(1))] }, comdat, align 8
 // GCN: @_ZTV1A = linkonce_odr unnamed_addr addrspace(1) constant { [4 x ptr addrspace(1)] } { [4 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr @__cxa_pure_virtual to ptr addrspace(1))] }, comdat, align 8
-// SPIRV: @_ZTV1C = linkonce_odr unnamed_addr addrspace(1) constant { [5 x ptr addrspace(1)], [4 x ptr addrspace(1)] } { [5 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1B2f2Ev to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1C2f1Ev to ptr addrspace(1))], [4 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 -8 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1C2f1Ev to ptr addrspace(1))] }, comdat, align 8
+// SPIRV: @_ZTV1C = linkonce_odr unnamed_addr addrspace(1) constant { [5 x ptr addrspace(1)], [4 x ptr addrspace(1)] } { [5 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1B2f2Ev to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1C2f1Ev to ptr addrspace(1))], [4 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 -8 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZThn8_N1C2f1Ev to ptr addrspace(1))] }, comdat, align 8
 // SPIRV: @_ZTV1B = linkonce_odr unnamed_addr addrspace(1) constant { [3 x ptr addrspace(1)] } { [3 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @_ZN1B2f2Ev to ptr addrspace(1))] }, comdat, align 8
 // SPIRV: @_ZTV1A = linkonce_odr unnamed_addr addrspace(1) constant { [4 x ptr addrspace(1)] } { [4 x ptr addrspace(1)] [ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) addrspacecast (ptr addrspace(4) @__cxa_pure_virtual to ptr addrspace(1))] }, comdat, align 8