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Merged
merged 1 commit into from
Jul 9, 2025

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@tbaederr tbaederr commented Jul 8, 2025

Instead, return the new Pointer. This was weird before because some callers had to get the value from the stack again to perform further operations.

Instead, return the new Pointer. This was weird before because some
callers had to get the value from the stack again to perform further
operations.
@llvmbot llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" clang:bytecode Issues for the clang bytecode constexpr interpreter labels Jul 8, 2025
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llvmbot commented Jul 8, 2025

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

Instead, return the new Pointer. This was weird before because some callers had to get the value from the stack again to perform further operations.


Full diff: https://github.com/llvm/llvm-project/pull/147550.diff

1 Files Affected:

  • (modified) clang/lib/AST/ByteCode/Interp.h (+60-45)
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 85a07abb5ed01..9d17f96c97c85 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -2066,34 +2066,32 @@ inline bool CastMemberPtrPtr(InterpState &S, CodePtr OpPC) {
 //===----------------------------------------------------------------------===//
 
 template <class T, ArithOp Op>
-bool OffsetHelper(InterpState &S, CodePtr OpPC, const T &Offset,
-                  const Pointer &Ptr, bool IsPointerArith = false) {
+std::optional<Pointer> OffsetHelper(InterpState &S, CodePtr OpPC,
+                                    const T &Offset, const Pointer &Ptr,
+                                    bool IsPointerArith = false) {
   // A zero offset does not change the pointer.
-  if (Offset.isZero()) {
-    S.Stk.push<Pointer>(Ptr);
-    return true;
-  }
+  if (Offset.isZero())
+    return Ptr;
 
   if (IsPointerArith && !CheckNull(S, OpPC, Ptr, CSK_ArrayIndex)) {
     // The CheckNull will have emitted a note already, but we only
     // abort in C++, since this is fine in C.
     if (S.getLangOpts().CPlusPlus)
-      return false;
+      return std::nullopt;
   }
 
   // Arrays of unknown bounds cannot have pointers into them.
   if (!CheckArray(S, OpPC, Ptr))
-    return false;
+    return std::nullopt;
 
   // This is much simpler for integral pointers, so handle them first.
   if (Ptr.isIntegralPointer()) {
     uint64_t V = Ptr.getIntegerRepresentation();
     uint64_t O = static_cast<uint64_t>(Offset) * Ptr.elemSize();
     if constexpr (Op == ArithOp::Add)
-      S.Stk.push<Pointer>(V + O, Ptr.asIntPointer().Desc);
+      return Pointer(V + O, Ptr.asIntPointer().Desc);
     else
-      S.Stk.push<Pointer>(V - O, Ptr.asIntPointer().Desc);
-    return true;
+      return Pointer(V - O, Ptr.asIntPointer().Desc);
   } else if (Ptr.isFunctionPointer()) {
     uint64_t O = static_cast<uint64_t>(Offset);
     uint64_t N;
@@ -2105,8 +2103,7 @@ bool OffsetHelper(InterpState &S, CodePtr OpPC, const T &Offset,
     if (N > 1)
       S.CCEDiag(S.Current->getSource(OpPC), diag::note_constexpr_array_index)
           << N << /*non-array*/ true << 0;
-    S.Stk.push<Pointer>(Ptr.asFunctionPointer().getFunction(), N);
-    return true;
+    return Pointer(Ptr.asFunctionPointer().getFunction(), N);
   }
 
   assert(Ptr.isBlockPointer());
@@ -2156,7 +2153,7 @@ bool OffsetHelper(InterpState &S, CodePtr OpPC, const T &Offset,
   }
 
   if (Invalid && S.getLangOpts().CPlusPlus)
-    return false;
+    return std::nullopt;
 
   // Offset is valid - compute it on unsigned.
   int64_t WideIndex = static_cast<int64_t>(Index);
@@ -2172,15 +2169,11 @@ bool OffsetHelper(InterpState &S, CodePtr OpPC, const T &Offset,
   // we don't get here.
   if (Result == 0 && Ptr.isOnePastEnd()) {
     if (Ptr.getFieldDesc()->isArray())
-      S.Stk.push<Pointer>(Ptr.atIndex(0));
-    else
-      S.Stk.push<Pointer>(Ptr.asBlockPointer().Pointee,
-                          Ptr.asBlockPointer().Base);
-    return true;
+      return Ptr.atIndex(0);
+    return Pointer(Ptr.asBlockPointer().Pointee, Ptr.asBlockPointer().Base);
   }
 
-  S.Stk.push<Pointer>(Ptr.atIndex(static_cast<uint64_t>(Result)));
-  return true;
+  return Ptr.atIndex(static_cast<uint64_t>(Result));
 }
 
 template <PrimType Name, class T = typename PrimConv<Name>::T>
@@ -2189,16 +2182,26 @@ bool AddOffset(InterpState &S, CodePtr OpPC) {
   Pointer Ptr = S.Stk.pop<Pointer>();
   if (Ptr.isBlockPointer())
     Ptr = Ptr.expand();
-  return OffsetHelper<T, ArithOp::Add>(S, OpPC, Offset, Ptr,
-                                       /*IsPointerArith=*/true);
+
+  if (std::optional<Pointer> Result = OffsetHelper<T, ArithOp::Add>(
+          S, OpPC, Offset, Ptr, /*IsPointerArith=*/true)) {
+    S.Stk.push<Pointer>(*Result);
+    return true;
+  }
+  return false;
 }
 
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool SubOffset(InterpState &S, CodePtr OpPC) {
   const T &Offset = S.Stk.pop<T>();
   const Pointer &Ptr = S.Stk.pop<Pointer>();
-  return OffsetHelper<T, ArithOp::Sub>(S, OpPC, Offset, Ptr,
-                                       /*IsPointerArith=*/true);
+
+  if (std::optional<Pointer> Result = OffsetHelper<T, ArithOp::Sub>(
+          S, OpPC, Offset, Ptr, /*IsPointerArith=*/true)) {
+    S.Stk.push<Pointer>(*Result);
+    return true;
+  }
+  return false;
 }
 
 template <ArithOp Op>
@@ -2218,12 +2221,13 @@ static inline bool IncDecPtrHelper(InterpState &S, CodePtr OpPC,
 
   // Now the current Ptr again and a constant 1.
   OneT One = OneT::from(1);
-  if (!OffsetHelper<OneT, Op>(S, OpPC, One, P, /*IsPointerArith=*/true))
-    return false;
-
-  // Store the new value.
-  Ptr.deref<Pointer>() = S.Stk.pop<Pointer>();
-  return true;
+  if (std::optional<Pointer> Result =
+          OffsetHelper<OneT, Op>(S, OpPC, One, P, /*IsPointerArith=*/true)) {
+    // Store the new value.
+    Ptr.deref<Pointer>() = *Result;
+    return true;
+  }
+  return false;
 }
 
 static inline bool IncPtr(InterpState &S, CodePtr OpPC) {
@@ -2925,16 +2929,22 @@ inline bool ArrayElemPtr(InterpState &S, CodePtr OpPC) {
 
   if (Offset.isZero()) {
     if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) {
-      S.Stk.push<Pointer>(Ptr.atIndex(0));
-    } else {
-      S.Stk.push<Pointer>(Ptr);
+      S.Stk.push<Pointer>(Ptr.atIndex(0).narrow());
+      return true;
     }
-  } else {
-    if (!OffsetHelper<T, ArithOp::Add>(S, OpPC, Offset, Ptr))
-      return false;
+    S.Stk.push<Pointer>(Ptr);
+    return true;
+  }
+
+  assert(!Offset.isZero());
+
+  if (std::optional<Pointer> Result =
+          OffsetHelper<T, ArithOp::Add>(S, OpPC, Offset, Ptr)) {
+    S.Stk.push<Pointer>(Result->narrow());
+    return true;
   }
 
-  return NarrowPtr(S, OpPC);
+  return false;
 }
 
 template <PrimType Name, class T = typename PrimConv<Name>::T>
@@ -2949,16 +2959,21 @@ inline bool ArrayElemPtrPop(InterpState &S, CodePtr OpPC) {
 
   if (Offset.isZero()) {
     if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) {
-      S.Stk.push<Pointer>(Ptr.atIndex(0));
-    } else {
-      S.Stk.push<Pointer>(Ptr);
+      S.Stk.push<Pointer>(Ptr.atIndex(0).narrow());
+      return true;
     }
-  } else {
-    if (!OffsetHelper<T, ArithOp::Add>(S, OpPC, Offset, Ptr))
-      return false;
+    S.Stk.push<Pointer>(Ptr);
+    return true;
   }
 
-  return NarrowPtr(S, OpPC);
+  assert(!Offset.isZero());
+
+  if (std::optional<Pointer> Result =
+          OffsetHelper<T, ArithOp::Add>(S, OpPC, Offset, Ptr)) {
+    S.Stk.push<Pointer>(Result->narrow());
+    return true;
+  }
+  return false;
 }
 
 template <PrimType Name, class T = typename PrimConv<Name>::T>

@tbaederr tbaederr merged commit 4581e5a into llvm:main Jul 9, 2025
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