[SYCL] Don't run SYCLOptimizeBarriersPass with O0 (#20037)

Signed-off-by: Sidorov, Dmitry <[email protected]>

Author: MrSidims

clang/lib/CodeGen/BackendUtil.cpp

@@ -1093,8 +1093,9 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
              ThinOrFullLTOPhase) {
             MPM.addPass(createModuleToFunctionPassAdaptor(
                 InferAddressSpacesPass(clang::targets::SPIR_GENERIC_AS)));
-            MPM.addPass(
-                createModuleToFunctionPassAdaptor(SYCLOptimizeBarriersPass()));
+            if (Level != OptimizationLevel::O0)
+              MPM.addPass(createModuleToFunctionPassAdaptor(
+                  SYCLOptimizeBarriersPass()));
           });
     }
 

clang/test/CodeGenSYCL/kernel-early-optimization-pipeline.cpp

@@ -12,6 +12,7 @@
 // CHECK: InferFunctionAttrsPass
 // CHECK: AlwaysInlinerPass
 // CHECK: ModuleInlinerWrapperPass
+// CHECK: SYCLOptimizeBarriersPass
 // CHECK: ConstantMergePass
 // CHECK: SYCLMutatePrintfAddrspacePass
 // CHECK: SYCLPropagateAspectsUsagePass
@@ -22,4 +23,13 @@
 //
 // RUN: %clang_cc1 -O2 -fsycl-is-device -triple spir64-unknown-unknown %s -mdebug-pass Structure -emit-llvm -fno-sycl-early-optimizations -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-NOEARLYOPT
 // CHECK-NOEARLYOPT-NOT: ConstantMergePass1
+// CHECK-NOEARLYOPT-NOT: SYCLOptimizeBarriersPass
 // CHECK-NOEARLYOPT: SYCLMutatePrintfAddrspacePass
+
+// RUN: %clang_cc1 -O0 -fsycl-is-device -triple spir64-unknown-unknown %s -mdebug-pass Structure -emit-llvm -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O0
+// CHECK-O0-NOT: SYCLOptimizeBarriersPass
+
+// Passes registered via registerOptimizerLastEPCallback don't run on empty
+// code
+__attribute__((sycl_device)) void bar() {
+}