Skip function declarations in the SLM resolution pass

Function declarations have no basic blocks and instructions, so they
should be skipped in the SLM resolution pass.

Author: vmustya

IGC/VectorCompiler/lib/GenXCodeGen/GenXSLMResolution.cpp

@@ -279,9 +279,12 @@ bool GenXSLMResolution::runOnModule(Module &M) {
 
   auto SLMVars = collectSLMVariables(M);
   if (!SLMVars.empty())
-    for (auto &F : M.functions())
+    for (auto &F : M.functions()) {
+      if (F.isDeclaration())
+        continue;
       Modified |=
           vc::breakConstantExprs(&F, vc::LegalizationStage::NotLegalized);
+    }
 
   for (auto &F : M.functions())
     if (vc::isKernel(&F))

IGC/VectorCompiler/test/GenXSLMResolution/simple.ll

@@ -30,13 +30,20 @@ define dllexport spir_kernel void @kernel() #0 {
   ; CHECK-OPAQUE-PTRS: %load_struct_i64i8 = load { i64, i8 }, ptr addrspace(3) inttoptr (i32 8 to ptr addrspace(3))
   %load_struct_i64i8 = load { i64, i8 }, { i64, i8 } addrspace(3)* @slm_struct_i64i8
 
+  ; CHECK-TYPED-PTRS: call void @llvm.genx.barrier()
+  ; CHECK-OPAQUE-PTRS: call void @llvm.genx.barrier()
+  call void @llvm.genx.barrier()
+
   ; CHECK-TYPED-PTRS: %load_struct_align = load { i1 }, { i1 } addrspace(3)* inttoptr (i32 268435456 to { i1 } addrspace(3)*)
   ; CHECK-OPAQUE-PTRS: %load_struct_align = load { i1 }, ptr addrspace(3) inttoptr (i32 268435456 to ptr addrspace(3))
   %load_struct_align = load { i1 }, { i1 } addrspace(3)* @slm_struct_align
   ret void
 }
 
+declare void @llvm.genx.barrier() #1
+
 attributes #0 = { noinline nounwind "CMGenxMain" }
+attributes #1 = { nounwind convergent }
 
 !genx.kernels = !{!0}
 !genx.kernel.internal = !{!3}