[clang][bytecode] Implement __builtin_assume_aligned (llvm#111968)

Author: tbaederr

clang/lib/AST/ByteCode/InterpBuiltin.cpp

@@ -38,7 +38,6 @@ static T getParam(const InterpFrame *Frame, unsigned Index) {
   return Frame->getParam<T>(Offset);
 }
 
-// static APSInt getAPSIntParam(InterpStack &Stk, size_t Offset = 0) {
 static APSInt getAPSIntParam(const InterpFrame *Frame, unsigned Index) {
   APSInt R;
   unsigned Offset = Frame->getFunction()->getParamOffset(Index);
@@ -1162,6 +1161,71 @@ static bool interp__builtin_is_aligned_up_down(InterpState &S, CodePtr OpPC,
   return false;
 }
 
+/// __builtin_assume_aligned(Ptr, Alignment[, ExtraOffset])
+static bool interp__builtin_assume_aligned(InterpState &S, CodePtr OpPC,
+                                           const InterpFrame *Frame,
+                                           const Function *Func,
+                                           const CallExpr *Call) {
+  assert(Call->getNumArgs() == 2 || Call->getNumArgs() == 3);
+
+  // Might be called with function pointers in C.
+  std::optional<PrimType> PtrT = S.Ctx.classify(Call->getArg(0));
+  if (PtrT != PT_Ptr)
+    return false;
+
+  unsigned ArgSize = callArgSize(S, Call);
+  const Pointer &Ptr = S.Stk.peek<Pointer>(ArgSize);
+  std::optional<APSInt> ExtraOffset;
+  APSInt Alignment;
+  if (Call->getNumArgs() == 2) {
+    Alignment = peekToAPSInt(S.Stk, *S.Ctx.classify(Call->getArg(1)));
+  } else {
+    PrimType AlignmentT = *S.Ctx.classify(Call->getArg(1));
+    PrimType ExtraOffsetT = *S.Ctx.classify(Call->getArg(2));
+    Alignment = peekToAPSInt(S.Stk, *S.Ctx.classify(Call->getArg(1)),
+                             align(primSize(AlignmentT)) +
+                                 align(primSize(ExtraOffsetT)));
+    ExtraOffset = peekToAPSInt(S.Stk, *S.Ctx.classify(Call->getArg(2)));
+  }
+
+  CharUnits Align = CharUnits::fromQuantity(Alignment.getZExtValue());
+
+  // If there is a base object, then it must have the correct alignment.
+  if (Ptr.isBlockPointer()) {
+    CharUnits BaseAlignment;
+    if (const auto *VD = Ptr.getDeclDesc()->asValueDecl())
+      BaseAlignment = S.getASTContext().getDeclAlign(VD);
+    else if (const auto *E = Ptr.getDeclDesc()->asExpr())
+      BaseAlignment = GetAlignOfExpr(S.getASTContext(), E, UETT_AlignOf);
+
+    if (BaseAlignment < Align) {
+      S.CCEDiag(Call->getArg(0),
+                diag::note_constexpr_baa_insufficient_alignment)
+          << 0 << BaseAlignment.getQuantity() << Align.getQuantity();
+      return false;
+    }
+  }
+
+  APValue AV = Ptr.toAPValue(S.getASTContext());
+  CharUnits AVOffset = AV.getLValueOffset();
+  if (ExtraOffset)
+    AVOffset -= CharUnits::fromQuantity(ExtraOffset->getZExtValue());
+  if (AVOffset.alignTo(Align) != AVOffset) {
+    if (Ptr.isBlockPointer())
+      S.CCEDiag(Call->getArg(0),
+                diag::note_constexpr_baa_insufficient_alignment)
+          << 1 << AVOffset.getQuantity() << Align.getQuantity();
+    else
+      S.CCEDiag(Call->getArg(0),
+                diag::note_constexpr_baa_value_insufficient_alignment)
+          << AVOffset.getQuantity() << Align.getQuantity();
+    return false;
+  }
+
+  S.Stk.push<Pointer>(Ptr);
+  return true;
+}
+
 static bool interp__builtin_ia32_bextr(InterpState &S, CodePtr OpPC,
                                        const InterpFrame *Frame,
                                        const Function *Func,
@@ -1905,6 +1969,11 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
       return false;
     break;
 
+  case Builtin::BI__builtin_assume_aligned:
+    if (!interp__builtin_assume_aligned(S, OpPC, Frame, F, Call))
+      return false;
+    break;
+
   case clang::X86::BI__builtin_ia32_bextr_u32:
   case clang::X86::BI__builtin_ia32_bextr_u64:
   case clang::X86::BI__builtin_ia32_bextri_u32:

clang/lib/AST/ExprConstShared.h

@@ -14,12 +14,17 @@
 #ifndef LLVM_CLANG_LIB_AST_EXPRCONSTSHARED_H
 #define LLVM_CLANG_LIB_AST_EXPRCONSTSHARED_H
 
+#include "clang/Basic/TypeTraits.h"
+
 namespace llvm {
 class APFloat;
 }
 namespace clang {
 class QualType;
 class LangOptions;
+class ASTContext;
+class CharUnits;
+class Expr;
 } // namespace clang
 using namespace clang;
 /// Values returned by __builtin_classify_type, chosen to match the values
@@ -66,4 +71,7 @@ void HandleComplexComplexDiv(llvm::APFloat A, llvm::APFloat B, llvm::APFloat C,
                              llvm::APFloat D, llvm::APFloat &ResR,
                              llvm::APFloat &ResI);
 
+CharUnits GetAlignOfExpr(const ASTContext &Ctx, const Expr *E,
+                         UnaryExprOrTypeTrait ExprKind);
+
 #endif

clang/lib/AST/ExprConstant.cpp

@@ -9620,7 +9620,7 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
   return ExprEvaluatorBaseTy::VisitCastExpr(E);
 }
 
-static CharUnits GetAlignOfType(EvalInfo &Info, QualType T,
+static CharUnits GetAlignOfType(const ASTContext &Ctx, QualType T,
                                 UnaryExprOrTypeTrait ExprKind) {
   // C++ [expr.alignof]p3:
   //     When alignof is applied to a reference type, the result is the
@@ -9631,23 +9631,22 @@ static CharUnits GetAlignOfType(EvalInfo &Info, QualType T,
     return CharUnits::One();
 
   const bool AlignOfReturnsPreferred =
-      Info.Ctx.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver7;
+      Ctx.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver7;
 
   // __alignof is defined to return the preferred alignment.
   // Before 8, clang returned the preferred alignment for alignof and _Alignof
   // as well.
   if (ExprKind == UETT_PreferredAlignOf || AlignOfReturnsPreferred)
-    return Info.Ctx.toCharUnitsFromBits(
-      Info.Ctx.getPreferredTypeAlign(T.getTypePtr()));
+    return Ctx.toCharUnitsFromBits(Ctx.getPreferredTypeAlign(T.getTypePtr()));
   // alignof and _Alignof are defined to return the ABI alignment.
   else if (ExprKind == UETT_AlignOf)
-    return Info.Ctx.getTypeAlignInChars(T.getTypePtr());
+    return Ctx.getTypeAlignInChars(T.getTypePtr());
   else
     llvm_unreachable("GetAlignOfType on a non-alignment ExprKind");
 }
 
-static CharUnits GetAlignOfExpr(EvalInfo &Info, const Expr *E,
-                                UnaryExprOrTypeTrait ExprKind) {
+CharUnits GetAlignOfExpr(const ASTContext &Ctx, const Expr *E,
+                         UnaryExprOrTypeTrait ExprKind) {
   E = E->IgnoreParens();
 
   // The kinds of expressions that we have special-case logic here for
@@ -9657,22 +9656,22 @@ static CharUnits GetAlignOfExpr(EvalInfo &Info, const Expr *E,
   // alignof decl is always accepted, even if it doesn't make sense: we default
   // to 1 in those cases.
   if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
-    return Info.Ctx.getDeclAlign(DRE->getDecl(),
-                                 /*RefAsPointee*/true);
+    return Ctx.getDeclAlign(DRE->getDecl(),
+                            /*RefAsPointee*/ true);
 
   if (const MemberExpr *ME = dyn_cast<MemberExpr>(E))
-    return Info.Ctx.getDeclAlign(ME->getMemberDecl(),
-                                 /*RefAsPointee*/true);
+    return Ctx.getDeclAlign(ME->getMemberDecl(),
+                            /*RefAsPointee*/ true);
 
-  return GetAlignOfType(Info, E->getType(), ExprKind);
+  return GetAlignOfType(Ctx, E->getType(), ExprKind);
 }
 
 static CharUnits getBaseAlignment(EvalInfo &Info, const LValue &Value) {
   if (const auto *VD = Value.Base.dyn_cast<const ValueDecl *>())
     return Info.Ctx.getDeclAlign(VD);
   if (const auto *E = Value.Base.dyn_cast<const Expr *>())
-    return GetAlignOfExpr(Info, E, UETT_AlignOf);
-  return GetAlignOfType(Info, Value.Base.getTypeInfoType(), UETT_AlignOf);
+    return GetAlignOfExpr(Info.Ctx, E, UETT_AlignOf);
+  return GetAlignOfType(Info.Ctx, Value.Base.getTypeInfoType(), UETT_AlignOf);
 }
 
 /// Evaluate the value of the alignment argument to __builtin_align_{up,down},
@@ -14475,11 +14474,11 @@ bool IntExprEvaluator::VisitUnaryExprOrTypeTraitExpr(
   case UETT_PreferredAlignOf:
   case UETT_AlignOf: {
     if (E->isArgumentType())
-      return Success(GetAlignOfType(Info, E->getArgumentType(), E->getKind()),
-                     E);
+      return Success(
+          GetAlignOfType(Info.Ctx, E->getArgumentType(), E->getKind()), E);
     else
-      return Success(GetAlignOfExpr(Info, E->getArgumentExpr(), E->getKind()),
-                     E);
+      return Success(
+          GetAlignOfExpr(Info.Ctx, E->getArgumentExpr(), E->getKind()), E);
   }
 
   case UETT_PtrAuthTypeDiscriminator: {

clang/test/Sema/builtin-assume-aligned.c

@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 -DSIZE_T_64 -fsyntax-only -Wno-strict-prototypes -triple x86_64-linux -verify %s
 // RUN: %clang_cc1 -fsyntax-only -Wno-strict-prototypes -triple i386-freebsd -verify %s
+// RUN: %clang_cc1 -DSIZE_T_64 -fsyntax-only -Wno-strict-prototypes -triple x86_64-linux -verify %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -fsyntax-only -Wno-strict-prototypes -triple i386-freebsd -verify %s -fexperimental-new-constant-interpreter
 
 // __builtin_assume_aligned's second parameter is size_t, which may be 32 bits,
 // so test differently when size_t is 32 bits and when it is 64 bits.

clang/test/SemaCXX/builtin-assume-aligned.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -triple x86_64-linux-gnu %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -triple x86_64-linux-gnu %s -fexperimental-new-constant-interpreter
 
 int n;
 constexpr int *p = 0;