[ESIMD] Remove propagation of sycl_explicit_simd to the callees (#3152)

We don't need to mark the ESIMD CFG since all ESIMD-specific passes will work exclusively on the ESIMD code. So, in ESIMD passes we don't have to worry about breaking other SYCL code.

Another important reason why we no longer need sycl_explicit_simd at every function in the call graph is that we decided that callgraph traversal and SYCL-ESIMD split will now be done in sycl-post-link rather than FE.

Author: DenisBakhvalov

clang/include/clang/Sema/Sema.h

@@ -12996,7 +12996,6 @@ class Sema final {
   void checkSYCLDeviceVarDecl(VarDecl *Var);
   void ConstructOpenCLKernel(FunctionDecl *KernelCallerFunc, MangleContext &MC);
   void MarkDevice();
-  void MarkSyclSimd();
 
   /// Emit a diagnostic about the given attribute having a deprecated name, and
   /// also emit a fixit hint to generate the new attribute name.

clang/lib/Sema/Sema.cpp

@@ -1014,8 +1014,6 @@ void Sema::ActOnEndOfTranslationUnitFragment(TUFragmentKind Kind) {
       SyclIntHeader->emit(getLangOpts().SYCLIntHeader);
     MarkDevice();
   }
-  if (getLangOpts().SYCLExplicitSIMD)
-    MarkSyclSimd();
 
   emitDeferredDiags();
 

clang/lib/Sema/SemaSYCL.cpp

@@ -552,12 +552,6 @@ class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
         }
       }
 
-      // Propagate the explicit SIMD attribute through call graph - it is used
-      // to distinguish ESIMD code in ESIMD LLVM passes.
-      if (KernelBody && KernelBody->hasAttr<SYCLSimdAttr>() &&
-          (KernelBody != FD) && !FD->hasAttr<SYCLSimdAttr>())
-        FD->addAttr(SYCLSimdAttr::CreateImplicit(SemaRef.getASTContext()));
-
       // Attribute "loop_fuse" can be applied explicitly on kernel function.
       // Attribute should not be propagated from device functions to kernel.
       if (auto *A = FD->getAttr<SYCLIntelLoopFuseAttr>()) {
@@ -3210,27 +3204,6 @@ void Sema::ConstructOpenCLKernel(FunctionDecl *KernelCallerFunc,
   Visitor.VisitRecordFields(KernelObj, kernel_decl, kernel_body, int_header);
 }
 
-// This function marks all the callees of explicit SIMD kernel
-// with !sycl_explicit_simd. We want to have different semantics
-// for functions that are called from SYCL and E-SIMD contexts.
-// Later, functions marked with !sycl_explicit_simd will be cloned
-// to maintain two different semantics.
-void Sema::MarkSyclSimd() {
-  for (Decl *D : syclDeviceDecls())
-    if (auto SYCLKernel = dyn_cast<FunctionDecl>(D))
-      if (SYCLKernel->hasAttr<SYCLSimdAttr>()) {
-        MarkDeviceFunction Marker(*this);
-        Marker.SYCLCG.addToCallGraph(getASTContext().getTranslationUnitDecl());
-        llvm::SmallPtrSet<FunctionDecl *, 10> VisitedSet;
-        Marker.CollectKernelSet(SYCLKernel, SYCLKernel, VisitedSet);
-        for (const auto &elt : Marker.KernelSet) {
-          if (FunctionDecl *Def = elt->getDefinition())
-            if (!Def->hasAttr<SYCLSimdAttr>())
-              Def->addAttr(SYCLSimdAttr::CreateImplicit(getASTContext()));
-        }
-      }
-}
-
 void Sema::MarkDevice(void) {
   // Create the call graph so we can detect recursion and check the validity
   // of new operator overrides. Add the kernel function itself in case

clang/test/CodeGenSYCL/esimd_metadata2.cpp

@@ -1,10 +1,7 @@
 // RUN: %clang_cc1 -disable-llvm-passes -triple spir64-unknown-unknown-sycldevice -fsycl -fsycl-is-device -fsycl-explicit-simd -S -emit-llvm %s -o - | FileCheck %s --check-prefixes CHECK,CHECK-ESIMD
 
-// In ESIMD mode:
-// 1. Attribute !intel_reqd_sub_group_size !1 is added
-//    for kernels with !sycl_explicit_simd
-// 2. Attribute !sycl_explicit_simd is propagated to all the
-//    callees of ESIMD kernel.
+// This test checks that attribute !intel_reqd_sub_group_size !1
+// is added for kernels with !sycl_explicit_simd
 
 __attribute__((sycl_device)) void shared_func_decl();
 __attribute__((sycl_device)) void shared_func() { shared_func_decl(); }
@@ -13,7 +10,7 @@ __attribute__((sycl_device)) __attribute__((sycl_explicit_simd)) void esimd_func
 
 // CHECK-ESIMD-DAG: define {{.*}}spir_kernel void @{{.*}}kernel_cm() #{{[0-9]+}} !sycl_explicit_simd !{{[0-9]+}} {{.*}} !intel_reqd_sub_group_size ![[SGSIZE1:[0-9]+]] {{.*}}{
 // CHECK-ESIMD-DAG: define {{.*}}spir_func void @{{.*}}esimd_funcv() #{{[0-9]+}} !sycl_explicit_simd !{{[0-9]+}} {
-// CHECK-ESIMD-DAG: define {{.*}}spir_func void @{{.*}}shared_funcv() #{{[0-9]+}} !sycl_explicit_simd !{{[0-9]+}} {
+// CHECK-ESIMD-DAG: define {{.*}}spir_func void @{{.*}}shared_funcv() #{{[0-9]+}} {
 // CHECK-ESIMD-DAG: define linkonce_odr spir_func void @_ZN12ESIMDFunctorclEv({{.*}}) #{{[0-9]+}} {{.*}} !sycl_explicit_simd !{{[0-9]+}} {
 // CHECK-ESIMD-DAG: declare spir_func void @{{.*}}shared_func_declv() #{{[0-9]+}}