[SYCL] Update aspect propagation logic for virtual functions

Author: jzc

llvm/lib/SYCLLowerIR/SYCLPropagateAspectsUsage.cpp

@@ -665,6 +665,24 @@ void processDeclaredVirtualFunctionSets(
     StringMap<SmallVector<Function *, 4>> &VirtualFunctionSets) {
   if (!F->hasFnAttribute("calls-indirectly"))
     return;
+
+  // "Construction" kernels which reference vtables but do not actually
+  // perform any virtual calls have the calls-indirectly attribute
+  // attached by SYCLVirtualFunctionAnalysis pass. We do not want to
+  // attach sycl_used_aspects metadata to such kernels.
+  bool hasVirtualCall = false;
+  for (const Instruction &I : instructions(F)) {
+    const auto *CI = dyn_cast<CallInst>(&I);
+    if (!CI)
+      continue;
+    if (CI->isIndirectCall() && CI->hasFnAttr("virtual-call")) {
+      hasVirtualCall = true;
+      break;
+    }
+  }
+  if (!hasVirtualCall)
+    return;
+
   Attribute CallsIndirectlyAttr = F->getFnAttribute("calls-indirectly");
   SmallVector<StringRef, 4> DeclaredVirtualFunctionSetNames;
   CallsIndirectlyAttr.getValueAsString().split(DeclaredVirtualFunctionSetNames,

llvm/test/SYCLLowerIR/PropagateAspectsUsage/VirtualFunctions/virtual-functions-1.ll

@@ -6,15 +6,17 @@ define spir_func void @vfn() #0 {
   ret void
 }
 
-; CHECK: @foo() #1 !sycl_used_aspects ![[#aspects]]
-define spir_kernel void @foo() #1 {
+; CHECK: @foo({{.*}}) #1 !sycl_used_aspects ![[#aspects]]
+define spir_kernel void @foo(ptr %f) #1 {
+  call void %f() #2
   ret void
 }
 
 ; CHECK: ![[#aspects]] = !{i32 6}
 
 attributes #0 = { "indirectly-callable"="_ZTSv" }
 attributes #1 = { "calls-indirectly"="_ZTSv" }
+attributes #2 = { "virtual-call" }
 
 !sycl_aspects = !{!0}
 !0 = !{!"fp64", i32 6}

llvm/test/SYCLLowerIR/PropagateAspectsUsage/VirtualFunctions/virtual-functions-2.ll

@@ -15,8 +15,9 @@ define spir_func void @vfnBar() #1 {
   ret void
 }
 
-; CHECK: @kernel() #2 !sycl_used_aspects ![[#aspectsKernel:]]
-define spir_kernel void @kernel() #2 {
+; CHECK: @kernel({{.*}}) #2 !sycl_used_aspects ![[#aspectsKernel:]]
+define spir_kernel void @kernel(ptr %f) #2 {
+  call void %f() #3
   ret void
 }
 
@@ -27,6 +28,7 @@ define spir_kernel void @kernel() #2 {
 attributes #0 = { "indirectly-callable"="setFoo" }
 attributes #1 = { "indirectly-callable"="setBar" }
 attributes #2 = { "calls-indirectly"="setFoo,setBar" }
+attributes #3 = { "virtual-call" }
 
 !sycl_aspects = !{!0}
 !0 = !{!"fp64", i32 6}

llvm/test/SYCLLowerIR/PropagateAspectsUsage/VirtualFunctions/virtual-functions-3.ll

@@ -25,13 +25,15 @@ define spir_func void @subBar() {
   ret void
 }
 
-; CHECK: @kernelA() #2 !sycl_used_aspects ![[#aspectsFoo]]
-define spir_kernel void @kernelA() #2 {
+; CHECK: @kernelA({{.*}}) #2 !sycl_used_aspects ![[#aspectsFoo]]
+define spir_kernel void @kernelA(ptr %f) #2 {
+  call void %f() #4
   ret void
 }
 
-; CHECK: @kernelB() #3 !sycl_used_aspects ![[#aspectsBar]]
-define spir_kernel void @kernelB() #3 {
+; CHECK: @kernelB({{.*}}) #3 !sycl_used_aspects ![[#aspectsBar]]
+define spir_kernel void @kernelB(ptr %f) #3 {
+  call void %f() #4
   ret void
 }
 
@@ -42,6 +44,7 @@ attributes #0 = { "indirectly-callable"="setFoo" }
 attributes #1 = { "indirectly-callable"="setBar" }
 attributes #2 = { "calls-indirectly"="setFoo" }
 attributes #3 = { "calls-indirectly"="setBar" }
+attributes #4 = { "virtual-call" }
 
 !sycl_aspects = !{!0}
 !0 = !{!"fp64", i32 6}

llvm/test/SYCLLowerIR/PropagateAspectsUsage/VirtualFunctions/virtual-functions-4.ll

@@ -11,16 +11,29 @@ entry:
   ret void
 }
 
+; "Construction" kernels which reference vtables but do not actually
+; perform any virtual calls should not have aspects propagated to them.
 ; CHECK-NOT: @construct({{.*}}){{.*}}!sycl_used_aspects
 define weak_odr dso_local spir_kernel void @construct(ptr addrspace(1) noundef align 8 %_arg_StorageAcc) {
 entry:
   store ptr addrspace(1) getelementptr inbounds inrange(-16, 8) (i8, ptr addrspace(1) @vtable, i64 16), ptr addrspace(1) %_arg_StorageAcc, align 8
   ret void
 }
 
+; Note: after SYCLVirtualFunctionAnalysis pass, the construction kernels will have 
+; "calls-indirectly" attribute, but even so they should not have aspects propagated 
+; to them (as the construction kernels have no virtual calls).
+; CHECK-NOT: @construct2({{.*}}){{.*}}!sycl_used_aspects
+define weak_odr dso_local spir_kernel void @construct2(ptr addrspace(1) noundef align 8 %_arg_StorageAcc) #1 {
+entry:
+  store ptr addrspace(1) getelementptr inbounds inrange(-16, 8) (i8, ptr addrspace(1) @vtable, i64 16), ptr addrspace(1) %_arg_StorageAcc, align 8
+  ret void
+}
+
 ; CHECK: ![[#aspects]] = !{i32 6}
 
 attributes #0 = { "indirectly-callable"="set-foo" }
+attributes #1 = { "calls-indirectly"="set-foo" }
 
 !sycl_aspects = !{!0}
 !0 = !{!"fp64", i32 6}