[Clang] Add builtin_nondeterministic_value

Differential Revision: https://reviews.llvm.org/D142388

clang/docs/LanguageExtensions.rst

@@ -3081,6 +3081,32 @@ Query for this feature with ``__has_builtin(__builtin_debugtrap)``.
 
 Query for this feature with ``__has_builtin(__builtin_trap)``.
 
+``__builtin_nondeterministic_value``
+------------------------------------
+
+``__builtin_nondeterministic_value`` returns a valid nondeterministic value of the same type as the provided argument.
+
+**Syntax**:
+
+.. code-block:: c++
+
+    type __builtin_nondeterministic_value(type x)
+
+**Examples**:
+
+.. code-block:: c++
+
+    int x = __builtin_nondeterministic_value(x);
+    float y = __builtin_nondeterministic_value(y);
+    __m256i a = __builtin_nondeterministic_value(a);
+
+**Description**
+
+Each call to ``__builtin_nondeterministic_value`` returns a valid value of the type given by the argument.
+
+The types currently supported are: integer types, floating-point types, vector types.
+
+Query for this feature with ``__has_builtin(__builtin_nondeterministic_value)``.
 
 ``__builtin_sycl_unique_stable_name``
 -------------------------------------

clang/docs/ReleaseNotes.rst

@@ -79,6 +79,8 @@ Non-comprehensive list of changes in this release
 - Clang now saves the address of ABI-indirect function parameters on the stack,
   improving the debug information available in programs compiled without
   optimizations.
+- Clang now supports ``__builtin_nondeterministic_value`` that returns a
+  nondeterministic value of the same type as the provided argument.
 
 New Compiler Flags
 ------------------

clang/include/clang/Basic/Builtins.def

@@ -655,6 +655,7 @@ BUILTIN(__builtin_alloca_uninitialized, "v*z", "Fn")
 BUILTIN(__builtin_alloca_with_align, "v*zIz", "Fn")
 BUILTIN(__builtin_alloca_with_align_uninitialized, "v*zIz", "Fn")
 BUILTIN(__builtin_call_with_static_chain, "v.", "nt")
+BUILTIN(__builtin_nondeterministic_value, "v.", "nt")
 
 BUILTIN(__builtin_elementwise_abs, "v.", "nct")
 BUILTIN(__builtin_elementwise_max, "v.", "nct")

clang/include/clang/Sema/Sema.h

@@ -13571,6 +13571,8 @@ private:
   bool PrepareBuiltinElementwiseMathOneArgCall(CallExpr *TheCall);
   bool PrepareBuiltinReduceMathOneArgCall(CallExpr *TheCall);
 
+  bool SemaBuiltinNonDeterministicValue(CallExpr *TheCall);
+
   // Matrix builtin handling.
   ExprResult SemaBuiltinMatrixTranspose(CallExpr *TheCall,
                                         ExprResult CallResult);

clang/lib/CodeGen/CGBuiltin.cpp

@@ -3060,6 +3060,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(V);
   }
 
+  case Builtin::BI__builtin_nondeterministic_value: {
+    llvm::Type *Ty = ConvertType(E->getArg(0)->getType());
+
+    Value *Result = PoisonValue::get(Ty);
+    Result = Builder.CreateFreeze(Result);
+
+    return RValue::get(Result);
+  }
+
   case Builtin::BI__builtin_elementwise_abs: {
     Value *Result;
     QualType QT = E->getArg(0)->getType();

clang/lib/Sema/SemaChecking.cpp

@@ -2584,6 +2584,12 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
     break;
   }
 
+  case Builtin::BI__builtin_nondeterministic_value: {
+    if (SemaBuiltinNonDeterministicValue(TheCall))
+      return ExprError();
+    break;
+  }
+
   // __builtin_elementwise_abs restricts the element type to signed integers or
   // floating point types only.
   case Builtin::BI__builtin_elementwise_abs: {
@@ -17858,6 +17864,21 @@ bool Sema::PrepareBuiltinReduceMathOneArgCall(CallExpr *TheCall) {
   return false;
 }
 
+bool Sema::SemaBuiltinNonDeterministicValue(CallExpr *TheCall) {
+  if (checkArgCount(*this, TheCall, 1))
+    return true;
+
+  ExprResult Arg = TheCall->getArg(0);
+  QualType TyArg = Arg.get()->getType();
+
+  if (!TyArg->isBuiltinType() && !TyArg->isVectorType())
+    return Diag(TheCall->getArg(0)->getBeginLoc(), diag::err_builtin_invalid_arg_type)
+           << 1 << /*vector, integer or floating point ty*/ 0 << TyArg;
+
+  TheCall->setType(TyArg);
+  return false;
+}
+
 ExprResult Sema::SemaBuiltinMatrixTranspose(CallExpr *TheCall,
                                             ExprResult CallResult) {
   if (checkArgCount(*this, TheCall, 1))

clang/test/CodeGen/builtins-nondeterministic-value.c

@@ -0,0 +1,60 @@
+// RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s
+
+typedef float float4 __attribute__((ext_vector_type(4)));
+typedef _Bool bool4 __attribute__((ext_vector_type(4)));
+
+int clang_nondet_i( int x ) {
+// CHECK-LABEL: entry
+// CHECK: [[A:%.*]] = alloca i32, align 4
+// CHECK: store i32 [[X:%.*]], ptr [[A]], align 4
+// CHECK: [[R:%.*]] = freeze i32 poison
+// CHECK: ret i32 [[R]]
+  return __builtin_nondeterministic_value(x);
+}
+
+float clang_nondet_f( float x ) {
+// CHECK-LABEL: entry
+// CHECK: [[A:%.*]] = alloca float, align 4
+// CHECK: store float [[X:%.*]], ptr [[A]], align 4
+// CHECK: [[R:%.*]] = freeze float poison
+// CHECK: ret float [[R]]
+  return __builtin_nondeterministic_value(x);
+}
+
+double clang_nondet_d( double x ) {
+// CHECK-LABEL: entry
+// CHECK: [[A:%.*]] = alloca double, align 8
+// CHECK: store double [[X:%.*]], ptr [[A]], align 8
+// CHECK: [[R:%.*]] = freeze double poison
+// CHECK: ret double [[R]]
+  return __builtin_nondeterministic_value(x);
+}
+
+_Bool clang_nondet_b( _Bool x) {
+// CHECK-LABEL: entry
+// CHECK: [[A:%.*]] = alloca i8, align 1
+// CHECK: [[B:%.*]] = zext i1 %x to i8
+// CHECK: store i8 [[B]], ptr [[A]], align 1
+// CHECK: [[R:%.*]] = freeze i1 poison
+// CHECK: ret i1 [[R]]
+  return __builtin_nondeterministic_value(x);
+}
+
+void clang_nondet_fv( ) {
+// CHECK-LABEL: entry
+// CHECK: [[A:%.*]] = alloca <4 x float>, align 16
+// CHECK: [[R:%.*]] = freeze <4 x float> poison
+// CHECK: store <4 x float> [[R]], ptr [[A]], align 16
+// CHECK: ret void
+  float4 x = __builtin_nondeterministic_value(x);
+}
+
+void clang_nondet_bv( ) {
+// CHECK: [[A:%.*]] = alloca i8, align 1
+// CHECK: [[V:%.*]] = freeze <4 x i1> poison
+// CHECK: [[SV:%.*]] = shufflevector <4 x i1> [[V]], <4 x i1> poison, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
+// CHECK: [[BC:%.*]] = bitcast <8 x i1> [[SV]] to i8
+// CHECK: store i8 [[BC]], ptr [[A]], align 1
+// CHECK: ret void
+  bool4 x = __builtin_nondeterministic_value(x);
+}