Revert "[BPF] Attribute preserve_static_offset for structs"

This reverts commit cb13e92.
Buildbot reports MSAN failures in tests added in this commit:
https://lab.llvm.org/buildbot/#/builders/5/builds/38806

Failing tests:
  LLVM :: CodeGen/BPF/preserve-static-offset/load-arr-pai.ll
  LLVM :: CodeGen/BPF/preserve-static-offset/load-ptr-pai.ll
  LLVM :: CodeGen/BPF/preserve-static-offset/load-struct-pai.ll
  LLVM :: CodeGen/BPF/preserve-static-offset/load-union-pai.ll
  LLVM :: CodeGen/BPF/preserve-static-offset/store-pai.ll

Author: eddyz87

clang/include/clang/Basic/Attr.td

@@ -2024,14 +2024,6 @@ def BPFPreserveAccessIndex : InheritableAttr,
   let LangOpts = [COnly];
 }
 
-def BPFPreserveStaticOffset : InheritableAttr,
-                              TargetSpecificAttr<TargetBPF>  {
-  let Spellings = [Clang<"preserve_static_offset">];
-  let Subjects = SubjectList<[Record], ErrorDiag>;
-  let Documentation = [BPFPreserveStaticOffsetDocs];
-  let LangOpts = [COnly];
-}
-
 def BTFDeclTag : InheritableAttr {
   let Spellings = [Clang<"btf_decl_tag">];
   let Args = [StringArgument<"BTFDeclTag">];

clang/include/clang/Basic/AttrDocs.td

@@ -2199,43 +2199,6 @@ preserving struct or union member access debuginfo indices of this
 struct or union, similar to clang ``__builtin_preserve_access_index()``.
   }];
 }
-
-def BPFPreserveStaticOffsetDocs : Documentation {
-  let Category = DocCatFunction;
-  let Content = [{
-Clang supports the ``__attribute__((preserve_static_offset))``
-attribute for the BPF target. This attribute may be attached to a
-struct or union declaration. Reading or writing fields of types having
-such annotation is guaranteed to generate LDX/ST/STX instruction with
-offset corresponding to the field.
-
-For example:
-
-.. code-block:: c
-
-  struct foo {
-    int a;
-    int b;
-  };
-
-  struct bar {
-    int a;
-    struct foo b;
-  } __attribute__((preserve_static_offset));
-
-  void buz(struct bar *g) {
-    g->b.a = 42;
-  }
-
-The assignment to ``g``'s field would produce an ST instruction with
-offset 8: ``*(u32)(r1 + 8) = 42;``.
-
-Without this attribute generated instructions might be different,
-depending on optimizations behavior. E.g. the example above could be
-rewritten as ``r1 += 8; *(u32)(r1 + 0) = 42;``.
-  }];
-}
-
 def BTFDeclTagDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

clang/lib/CodeGen/CGExpr.cpp

@@ -3833,33 +3833,6 @@ static QualType getFixedSizeElementType(const ASTContext &ctx,
   return eltType;
 }
 
-static bool hasBPFPreserveStaticOffset(const RecordDecl *D) {
-  return D && D->hasAttr<BPFPreserveStaticOffsetAttr>();
-}
-
-static bool hasBPFPreserveStaticOffset(const Expr *E) {
-  if (!E)
-    return false;
-  QualType PointeeType = E->getType()->getPointeeType();
-  if (PointeeType.isNull())
-    return false;
-  if (const auto *BaseDecl = PointeeType->getAsRecordDecl())
-    return hasBPFPreserveStaticOffset(BaseDecl);
-  return false;
-}
-
-// Wraps Addr with a call to llvm.preserve.static.offset intrinsic.
-static Address wrapWithBPFPreserveStaticOffset(CodeGenFunction &CGF,
-                                               Address &Addr) {
-  if (!CGF.getTarget().getTriple().isBPF())
-    return Addr;
-
-  llvm::Function *Fn =
-      CGF.CGM.getIntrinsic(llvm::Intrinsic::preserve_static_offset);
-  llvm::CallInst *Call = CGF.Builder.CreateCall(Fn, {Addr.getPointer()});
-  return Address(Call, Addr.getElementType(), Addr.getAlignment());
-}
-
 /// Given an array base, check whether its member access belongs to a record
 /// with preserve_access_index attribute or not.
 static bool IsPreserveAIArrayBase(CodeGenFunction &CGF, const Expr *ArrayBase) {
@@ -3921,9 +3894,6 @@ static Address emitArraySubscriptGEP(CodeGenFunction &CGF, Address addr,
   CharUnits eltAlign =
     getArrayElementAlign(addr.getAlignment(), indices.back(), eltSize);
 
-  if (hasBPFPreserveStaticOffset(Base))
-    addr = wrapWithBPFPreserveStaticOffset(CGF, addr);
-
   llvm::Value *eltPtr;
   auto LastIndex = dyn_cast<llvm::ConstantInt>(indices.back());
   if (!LastIndex ||
@@ -4552,8 +4522,6 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
     Address Addr = base.getAddress(*this);
     unsigned Idx = RL.getLLVMFieldNo(field);
     const RecordDecl *rec = field->getParent();
-    if (hasBPFPreserveStaticOffset(rec))
-      Addr = wrapWithBPFPreserveStaticOffset(*this, Addr);
     if (!UseVolatile) {
       if (!IsInPreservedAIRegion &&
           (!getDebugInfo() || !rec->hasAttr<BPFPreserveAccessIndexAttr>())) {
@@ -4626,8 +4594,6 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
   }
 
   Address addr = base.getAddress(*this);
-  if (hasBPFPreserveStaticOffset(rec))
-    addr = wrapWithBPFPreserveStaticOffset(*this, addr);
   if (auto *ClassDef = dyn_cast<CXXRecordDecl>(rec)) {
     if (CGM.getCodeGenOpts().StrictVTablePointers &&
         ClassDef->isDynamicClass()) {

clang/lib/Sema/SemaDeclAttr.cpp

@@ -9036,9 +9036,6 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_BPFPreserveAccessIndex:
     handleBPFPreserveAccessIndexAttr(S, D, AL);
     break;
-  case ParsedAttr::AT_BPFPreserveStaticOffset:
-    handleSimpleAttribute<BPFPreserveStaticOffsetAttr>(S, D, AL);
-    break;
   case ParsedAttr::AT_BTFDeclTag:
     handleBTFDeclTagAttr(S, D, AL);
     break;

clang/test/CodeGen/bpf-preserve-static-offset-arr.c

@@ -23,7 +23,6 @@
 // CHECK-NEXT: Availability ((SubjectMatchRule_record, SubjectMatchRule_enum, SubjectMatchRule_enum_constant, SubjectMatchRule_field, SubjectMatchRule_function, SubjectMatchRule_namespace, SubjectMatchRule_objc_category, SubjectMatchRule_objc_implementation, SubjectMatchRule_objc_interface, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_objc_protocol, SubjectMatchRule_record, SubjectMatchRule_type_alias, SubjectMatchRule_variable))
 // CHECK-NEXT: AvailableOnlyInDefaultEvalMethod (SubjectMatchRule_type_alias)
 // CHECK-NEXT: BPFPreserveAccessIndex (SubjectMatchRule_record)
-// CHECK-NEXT: BPFPreserveStaticOffset (SubjectMatchRule_record)
 // CHECK-NEXT: BTFDeclTag (SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_record, SubjectMatchRule_field, SubjectMatchRule_type_alias)
 // CHECK-NEXT: BuiltinAlias (SubjectMatchRule_function)
 // CHECK-NEXT: CFAuditedTransfer (SubjectMatchRule_function)

clang/test/CodeGen/bpf-preserve-static-offset-bitfield.c

@@ -2469,10 +2469,6 @@ def int_preserve_struct_access_index : DefaultAttrsIntrinsic<[llvm_anyptr_ty],
                                                  [IntrNoMem,
                                                   ImmArg<ArgIndex<1>>,
                                                   ImmArg<ArgIndex<2>>]>;
-def int_preserve_static_offset : DefaultAttrsIntrinsic<[llvm_ptr_ty],
-                                                       [llvm_ptr_ty],
-                                                       [IntrNoMem, IntrSpeculatable,
-                                                        ReadNone <ArgIndex<0>>]>;
 
 //===------------ Intrinsics to perform common vector shuffles ------------===//
 

clang/test/CodeGen/bpf-preserve-static-offset-lvalue.c

@@ -37,43 +37,4 @@ let TargetPrefix = "bpf" in {  // All intrinsics start with "llvm.bpf."
   def int_bpf_compare : ClangBuiltin<"__builtin_bpf_compare">,
               Intrinsic<[llvm_i1_ty], [llvm_i32_ty, llvm_anyint_ty, llvm_anyint_ty],
               [IntrNoMem]>;
-  def int_bpf_getelementptr_and_load : ClangBuiltin<"__builtin_bpf_getelementptr_and_load">,
-              Intrinsic<[llvm_any_ty],
-                        [llvm_ptr_ty,     // base ptr for getelementptr
-                         llvm_i1_ty,      // volatile
-                         llvm_i8_ty,      // atomic order
-                         llvm_i8_ty,      // synscope id
-                         llvm_i8_ty,      // alignment
-                         llvm_i1_ty,      // inbounds
-                         llvm_vararg_ty], // indices for getelementptr insn
-                        [IntrNoCallback,
-                         IntrNoFree,
-                         IntrWillReturn,
-                         NoCapture <ArgIndex<0>>,
-                         ImmArg    <ArgIndex<1>>, // volatile
-                         ImmArg    <ArgIndex<2>>, // atomic order
-                         ImmArg    <ArgIndex<3>>, // synscope id
-                         ImmArg    <ArgIndex<4>>, // alignment
-                         ImmArg    <ArgIndex<5>>, // inbounds
-                        ]>;
-  def int_bpf_getelementptr_and_store : ClangBuiltin<"__builtin_bpf_getelementptr_and_store">,
-              Intrinsic<[],
-                        [llvm_any_ty,     // value to store
-                         llvm_ptr_ty,     // base ptr for getelementptr
-                         llvm_i1_ty,      // volatile
-                         llvm_i8_ty,      // atomic order
-                         llvm_i8_ty,      // syncscope id
-                         llvm_i8_ty,      // alignment
-                         llvm_i1_ty,      // inbounds
-                         llvm_vararg_ty], // indexes for getelementptr insn
-                        [IntrNoCallback,
-                         IntrNoFree,
-                         IntrWillReturn,
-                         NoCapture <ArgIndex<1>>,
-                         ImmArg    <ArgIndex<2>>, // volatile
-                         ImmArg    <ArgIndex<3>>, // atomic order
-                         ImmArg    <ArgIndex<4>>, // syncscope id
-                         ImmArg    <ArgIndex<5>>, // alignment
-                         ImmArg    <ArgIndex<6>>, // inbounds
-                        ]>;
 }