Revert "[Clang][Attribute] Introduce maybe_undef attribute for function arguments which accepts undef values"

This reverts commit a35c64ce23.

Reverting this commit as it causes various failures on LE and BE PPC bots.

clang/include/clang/Basic/Attr.td

@@ -2023,13 +2023,6 @@ def NoEscape : Attr {
   let Documentation = [NoEscapeDocs];
 }
 
-def MaybeUndef : InheritableAttr {
-  let Spellings = [Clang<"maybe_undef">];
-  let Subjects = SubjectList<[ParmVar]>;
-  let Documentation = [MaybeUndefDocs];
-  let SimpleHandler = 1;
-}
-
 def AssumeAligned : InheritableAttr {
   let Spellings = [GCC<"assume_aligned">];
   let Subjects = SubjectList<[ObjCMethod, Function]>;

clang/include/clang/Basic/AttrDocs.td

@@ -257,28 +257,6 @@ applies to copies of the block. For example:
   }];
 }
 
-def MaybeUndefDocs : Documentation {
-  let Category = DocCatVariable;
-  let Content = [{
-The ``maybe_undef`` attribute can be placed on a function parameter. It indicates
-that the parameter is allowed to use undef values. It informs the compiler
-to insert a freeze LLVM IR instruction on the function parameter.
-Please note that this is an attribute that is used as an internal
-implementation detail and not intended to be used by external users.
-
-In languages HIP, CUDA etc., some functions have multi-threaded semantics and
-it is enough for only one or some threads to provide defined arguments.
-Depending on semantics, undef arguments in some threads don't produce
-undefined results in the function call. Since, these functions accept undefined
-arguments, ``maybe_undef`` attribute can be placed.
-
-Sample usage:
-.. code-block:: c
-
-  void maybeundeffunc(int __attribute__((maybe_undef))param);
-  }];
-}
-
 def CarriesDependencyDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

clang/lib/CodeGen/CGCall.cpp

@@ -2046,27 +2046,6 @@ static bool DetermineNoUndef(QualType QTy, CodeGenTypes &Types,
   return false;
 }
 
-/// Check if the argument of a function has maybe_undef attribute.
-static bool IsArgumentMaybeUndef(const Decl *TargetDecl,
-                                 unsigned NumRequiredArgs, unsigned ArgNo) {
-  const auto *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl);
-  if (!FD)
-    return false;
-
-  // Assume variadic arguments do not have maybe_undef attribute.
-  if (ArgNo >= NumRequiredArgs)
-    return false;
-
-  // Check if argument has maybe_undef attribute.
-  if (ArgNo < FD->getNumParams()) {
-    const ParmVarDecl *Param = FD->getParamDecl(ArgNo);
-    if (Param && Param->hasAttr<MaybeUndefAttr>())
-      return true;
-  }
-
-  return false;
-}
-
 /// Construct the IR attribute list of a function or call.
 ///
 /// When adding an attribute, please consider where it should be handled:
@@ -4842,9 +4821,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
     unsigned FirstIRArg, NumIRArgs;
     std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);
 
-    bool ArgHasMaybeUndefAttr =
-        IsArgumentMaybeUndef(TargetDecl, CallInfo.getNumRequiredArgs(), ArgNo);
-
     switch (ArgInfo.getKind()) {
     case ABIArgInfo::InAlloca: {
       assert(NumIRArgs == 0);
@@ -4903,11 +4879,7 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
         // Make a temporary alloca to pass the argument.
         Address Addr = CreateMemTempWithoutCast(
             I->Ty, ArgInfo.getIndirectAlign(), "indirect-arg-temp");
-
+        IRCallArgs[FirstIRArg] = Addr.getPointer();
-        llvm::Value *Val = Addr.getPointer();
-        if (ArgHasMaybeUndefAttr)
-          Val = Builder.CreateFreeze(Addr.getPointer());
-        IRCallArgs[FirstIRArg] = Val;
 
         I->copyInto(*this, Addr);
       } else {
@@ -4965,10 +4937,7 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           // Create an aligned temporary, and copy to it.
           Address AI = CreateMemTempWithoutCast(
               I->Ty, ArgInfo.getIndirectAlign(), "byval-temp");
-          llvm::Value *Val = AI.getPointer();
+          IRCallArgs[FirstIRArg] = AI.getPointer();
-          if (ArgHasMaybeUndefAttr)
-            Val = Builder.CreateFreeze(AI.getPointer());
-          IRCallArgs[FirstIRArg] = Val;
 
           // Emit lifetime markers for the temporary alloca.
           llvm::TypeSize ByvalTempElementSize =
@@ -4987,13 +4956,9 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           auto *T = llvm::PointerType::getWithSamePointeeType(
               cast<llvm::PointerType>(V->getType()),
               CGM.getDataLayout().getAllocaAddrSpace());
-
+          IRCallArgs[FirstIRArg] = getTargetHooks().performAddrSpaceCast(
-          llvm::Value *Val = getTargetHooks().performAddrSpaceCast(
               *this, V, LangAS::Default, CGM.getASTAllocaAddressSpace(), T,
               true);
-          if (ArgHasMaybeUndefAttr)
-            Val = Builder.CreateFreeze(Val);
-          IRCallArgs[FirstIRArg] = Val;
         }
       }
       break;
@@ -5047,8 +5012,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
             V->getType() != IRFuncTy->getParamType(FirstIRArg))
           V = Builder.CreateBitCast(V, IRFuncTy->getParamType(FirstIRArg));
 
-        if (ArgHasMaybeUndefAttr)
-          V = Builder.CreateFreeze(V);
         IRCallArgs[FirstIRArg] = V;
         break;
       }
@@ -5093,8 +5056,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
         for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
           Address EltPtr = Builder.CreateStructGEP(Src, i);
           llvm::Value *LI = Builder.CreateLoad(EltPtr);
-          if (ArgHasMaybeUndefAttr)
-            LI = Builder.CreateFreeze(LI);
           IRCallArgs[FirstIRArg + i] = LI;
         }
       } else {
@@ -5111,9 +5072,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           if (ATy != nullptr && isa<RecordType>(I->Ty.getCanonicalType()))
             Load = EmitCMSEClearRecord(Load, ATy, I->Ty);
         }
-
-        if (ArgHasMaybeUndefAttr)
-          Load = Builder.CreateFreeze(Load);
         IRCallArgs[FirstIRArg] = Load;
       }
 
@@ -5159,8 +5117,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
         if (ABIArgInfo::isPaddingForCoerceAndExpand(eltType)) continue;
         Address eltAddr = Builder.CreateStructGEP(addr, i);
         llvm::Value *elt = Builder.CreateLoad(eltAddr);
-        if (ArgHasMaybeUndefAttr)
-          elt = Builder.CreateFreeze(elt);
         IRCallArgs[IRArgPos++] = elt;
       }
       assert(IRArgPos == FirstIRArg + NumIRArgs);

clang/lib/Sema/SemaDeclAttr.cpp

@@ -8634,9 +8634,6 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_NoEscape:
     handleNoEscapeAttr(S, D, AL);
     break;
-  case ParsedAttr::AT_MaybeUndef:
-    handleSimpleAttribute<MaybeUndefAttr>(S, D, AL);
-    break;
   case ParsedAttr::AT_AssumeAligned:
     handleAssumeAlignedAttr(S, D, AL);
     break;

clang/test/CodeGen/attr-maybeundef-template.cpp

@@ -1,43 +0,0 @@
-// RUN: %clang_cc1 -no-opaque-pointers -emit-llvm %s -o - | FileCheck %s
-
-// CHECK-LABEL: define{{.*}} void @{{.*}}test4{{.*}}(float
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[TMP2:%.*]] = alloca float, align 4
-// CHECK-NEXT:    store float [[TMP1:%.*]], float* [[TMP2:%.*]], align 4
-// CHECK-NEXT:    ret void
-
-// CHECK-LABEL: define{{.*}} void @{{.*}}test4{{.*}}(i32
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[TMP2:%.*]] = alloca i32, align 4
-// CHECK-NEXT:    store i32 [[TMP1:%.*]], i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:    ret void
-
-// CHECK-LABEL: define{{.*}} void @{{.*}}test{{.*}}(
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[TMP1:%.*]] = alloca i32, align 4
-// CHECK-NEXT:    [[TMP2:%.*]] = alloca float, align 4
-// CHECK-NEXT:    [[TMP3:%.*]] = load i32, i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:    [[TMP4:%.*]] = freeze i32 [[TMP3:%.*]]
-// CHECK-NEXT:    call void @{{.*}}test4{{.*}}(i32 noundef [[TMP4:%.*]])
-// CHECK-NEXT:    [[TMP5:%.*]] = load float, float* [[TMP2:%.*]], align 4
-// CHECK-NEXT:    [[TMP6:%.*]] = freeze float [[TMP5:%.*]]
-// CHECK-NEXT:    call void @{{.*}}test4{{.*}}(float noundef [[TMP6:%.*]])
-// CHECK-NEXT:    ret void
-
-template<class T>
-void test4(T __attribute__((maybe_undef)) arg) {
-  return;
-}
-
-template
-void test4<float>(float arg);
-
-template
-void test4<int>(int arg);
-
-void test() {
-    int Var1;
-    float Var2;
-    test4<int>(Var1);
-    test4<float>(Var2);
-}

clang/test/CodeGen/attr-maybeundef.c

@@ -1,109 +0,0 @@
-// RUN: %clang_cc1 -no-opaque-pointers -emit-llvm %s -o - | FileCheck %s
-
-#define __maybe_undef __attribute__((maybe_undef))
-
-// CHECK:      define{{.*}} void @t1(i32 noundef [[TMP1:%.*]], i32 noundef [[TMP2:%.*]], i32 noundef [[TMP3:%.*]])
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP4:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP5:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP6:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   store i32 [[TMP1:%.*]], i32* [[TMP4:%.*]], align 4
-// CHECK-NEXT:   store i32 [[TMP2:%.*]], i32* [[TMP5:%.*]], align 4
-// CHECK-NEXT:   store i32 [[TMP3:%.*]], i32* [[TMP6:%.*]], align 4
-// CHECK-NEXT:   ret void
-
-// CHECK:      define{{.*}} void @t2(i32 noundef [[TMP1:%.*]], i32 noundef [[TMP2:%.*]], i32 noundef [[TMP3:%.*]])
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP4:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP5:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP6:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   store i32 [[TMP1:%.*]], i32* [[TMP4:%.*]], align 4
-// CHECK-NEXT:   store i32 [[TMP2:%.*]], i32* [[TMP5:%.*]], align 4
-// CHECK-NEXT:   store i32 [[TMP3:%.*]], i32* [[TMP6:%.*]], align 4
-// CHECK-NEXT:   [[TMP7:%.*]] = load i32, i32* [[TMP4:%.*]], align 4
-// CHECK-NEXT:   [[TMP8:%.*]] = load i32, i32* [[TMP5:%.*]], align 4
-// CHECK-NEXT:   [[TMP9:%.*]] = load i32, i32* [[TMP6:%.*]], align 4
-// CHECK-NEXT:   [[TMP10:%.*]] = freeze i32 [[TMP8:%.*]]
-// CHECK-NEXT:   call void @t1(i32 noundef [[TMP7:%.*]], i32 noundef [[TMP10:%.*]], i32 noundef [[TMP9:%.*]])
-// CHECK-NEXT:   ret void
-
-void t1(int param1, int __maybe_undef param2, int param3) {}
-
-void t2(int param1, int param2, int param3) {
-    t1(param1, param2, param3);
-}
-
-// CHECK:      define{{.*}} void @TestVariadicFunction(i32 noundef [[TMP0:%.*]], ...)
-// CHECK-NEXT: entry:
-// CHECK-NEXT:  [[TMP1:%.*]] = alloca i32, align 4
-// CHECK-NEXT:  [[TMP2:%.*]] = alloca i32, align 4
-// CHECK-NEXT:  store i32 [[TMP0:%.*]], i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:  [[TMP3:%.*]] = load i32, i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:  [[TMP4:%.*]] = load i32, i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:  [[TMP5:%.*]] = load i32, i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:  [[TMP5:%.*]] = freeze i32 [[TMP2:%.*]]
-// CHECK-NEXT:  call void (i32, ...) @VariadicFunction(i32 noundef [[TMP6:%.*]], i32 noundef [[TMP4:%.*]], i32 noundef [[TMP5:%.*]])
-// CHECK-NEXT:  ret void
-
-// CHECK: declare{{.*}} void @VariadicFunction(i32 noundef, ...)
-
-void VariadicFunction(int __maybe_undef x, ...);
-void TestVariadicFunction(int x, ...) {
-  int Var;
-  return VariadicFunction(x, Var, Var);
-}
-
-// CHECK:      define{{.*}} void @other()
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP1:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP2:%.*]] = load i32, i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:   call void @func(i32 noundef [[TMP2:%.*]])
-// CHECK-NEXT:   [[TMP3:%.*]] = load i32, i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:   [[TMP4:%.*]] = freeze i32 [[TMP3:%.*]]
-// CHECK-NEXT:   call void @func1(i32 noundef [[TMP4:%.*]])
-// CHECK-NEXT:   ret void
-
-// CHECK:      define{{.*}} void @func(i32 noundef [[TMP1:%.*]])
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP2:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   store i32 [[TMP1:%.*]], i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:   ret void
-
-// CHECK:      define{{.*}} void @func1(i32 noundef [[TMP1:%.*]])
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP2:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   store i32 [[TMP1:%.*]], i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:   ret void
-
-void func(int param);
-void func1(int __maybe_undef param);
-
-void other() {
-  int Var;
-  func(Var);
-  func1(Var);
-}
-
-void func(__maybe_undef int param) {}
-void func1(int param) {}
-
-// CHECK:      define{{.*}} void @foo(i32 noundef [[TMP1:%.*]])
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP2:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   store i32 [[TMP1:%.*]], i32* [[TMP2:%.*]], align 4
-// CHECK-NEXT:   ret void
-
-// CHECK:      define{{.*}} void @bar()
-// CHECK-NEXT: entry:
-// CHECK-NEXT:   [[TMP1:%.*]] = alloca i32, align 4
-// CHECK-NEXT:   [[TMP2:%.*]] = load i32, i32* [[TMP1:%.*]], align 4
-// CHECK-NEXT:   call void @foo(i32 noundef [[TMP2:%.*]])
-// CHECK-NEXT:   ret void
-
-void foo(__maybe_undef int param);
-void foo(int param) {}
-
-void bar() {
-  int Var;
-  foo(Var);
-}

clang/test/CodeGenHIP/maybe_undef-attr-verify.hip

@@ -1,44 +0,0 @@
-// RUN: %clang_cc1 -no-opaque-pointers -triple amdgcn-amd-amdhsa -target-cpu gfx906 -x hip -fcuda-is-device -emit-llvm  %s \
-// RUN:   -o - | FileCheck %s
-
-// CHECK: define dso_local amdgpu_kernel void @_Z13shufflekernelv()
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[TMP1:%.*]] = alloca i32, align 4, addrspace(5)
-// CHECK-NEXT:    [[TMP2:%.*]] = alloca i32, align 4, addrspace(5)
-// CHECK-NEXT:    [[TMP3:%.*]] = addrspacecast i32 addrspace(5)* [[TMP1:%.*]] to i32*
-// CHECK-NEXT:    [[TMP4:%.*]] = addrspacecast i32 addrspace(5)* [[TMP2:%.*]] to i32*
-// CHECK-NEXT:    [[TMP5:%.*]] = load i32, i32* [[TMP3:%.*]], align 4
-// CHECK-NEXT:    [[TMP6:%.*]] = freeze i32 [[TMP5:%.*]]
-// CHECK-NEXT:    %call = call noundef i32 @_Z11__shfl_synciii(i32 noundef [[TMP6:%.*]], i32 noundef 64, i32 noundef 0) #4
-// CHECK-NEXT:    store i32 %call, i32* [[TMP4:%.*]], align 4
-// CHECK-NEXT:  ret void
-
-// CHECK: define linkonce_odr noundef i32 @_Z11__shfl_synciii(i32 noundef [[TMP1:%.*]], i32 noundef [[TMP2:%.*]], i32 noundef [[TMP3:%.*]])
-
-#define __global__ __attribute__((global))
-#define __device__ __attribute__((device))
-#define __maybe_undef __attribute__((maybe_undef))
-#define WARP_SIZE 64
-
-static constexpr int warpSize = __AMDGCN_WAVEFRONT_SIZE;
-
-__device__ static inline unsigned int __lane_id() {
-    return  __builtin_amdgcn_mbcnt_hi(
-        -1, __builtin_amdgcn_mbcnt_lo(-1, 0));
-}
-
-__device__
-inline
-int __shfl_sync(int __maybe_undef var, int src_lane, int width = warpSize) {
-    int self = __lane_id();
-    int index = src_lane + (self & ~(width-1));
-    return __builtin_amdgcn_ds_bpermute(index<<2, var);
-}
-
-__global__ void
-shufflekernel()
-{
-    int t;
-    int res;
-    res = __shfl_sync(t, WARP_SIZE, 0);
-}

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -83,7 +83,6 @@
 // CHECK-NEXT: Lockable (SubjectMatchRule_record)
 // CHECK-NEXT: MIGServerRoutine (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_block)
 // CHECK-NEXT: MSStruct (SubjectMatchRule_record)
-// CHECK-NEXT: MaybeUndef (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: MicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: MinSize (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: MinVectorWidth (SubjectMatchRule_function)

clang/test/Sema/attr-maybeundef.c

@@ -1,15 +0,0 @@
-// RUN: %clang_cc1  -fsyntax-only -verify %s
-
-// Decl annotations.
-void f(int __attribute__((maybe_undef)) *a);
-void (*fp)(int __attribute__((maybe_undef)) handle);
-__attribute__((maybe_undef)) int i(); // expected-warning {{'maybe_undef' attribute only applies to parameters}}
-int __attribute__((maybe_undef)) a; // expected-warning {{'maybe_undef' attribute only applies to parameters}}
-int (* __attribute__((maybe_undef)) fpt)(char *); // expected-warning {{'maybe_undef' attribute only applies to parameters}}
-void h(int *a __attribute__((maybe_undef("RandomString")))); // expected-error {{'maybe_undef' attribute takes no arguments}}
-
-// Type annotations.
-int __attribute__((maybe_undef)) ta; // expected-warning {{'maybe_undef' attribute only applies to parameters}}
-
-// Typedefs.
-typedef int callback(char *) __attribute__((maybe_undef)); // expected-warning {{'maybe_undef' attribute only applies to parameters}}