[clang] [clang][bytecode] Move pointers from extern globals to new decls (PR #154273)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/154273.diff


4 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBlock.h (+1) 
- (modified) clang/lib/AST/ByteCode/Pointer.h (+1) 
- (modified) clang/lib/AST/ByteCode/Program.cpp (+21-11) 
- (modified) clang/test/AST/ByteCode/literals.cpp (+7) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBlock.h b/clang/lib/AST/ByteCode/InterpBlock.h
index 1043fa0c55f32..ea9f44c38842e 100644
--- a/clang/lib/AST/ByteCode/InterpBlock.h
+++ b/clang/lib/AST/ByteCode/InterpBlock.h
@@ -149,6 +149,7 @@ class Block final {
   friend class DeadBlock;
   friend class InterpState;
   friend class DynamicAllocator;
+  friend class Program;
 
   Block(unsigned EvalID, const Descriptor *Desc, bool IsExtern, bool IsStatic,
         bool IsWeak, bool IsDummy, bool IsDead)
diff --git a/clang/lib/AST/ByteCode/Pointer.h b/clang/lib/AST/ByteCode/Pointer.h
index 1dcdc0424801d..27659d7eeaf09 100644
--- a/clang/lib/AST/ByteCode/Pointer.h
+++ b/clang/lib/AST/ByteCode/Pointer.h
@@ -804,6 +804,7 @@ class Pointer {
   friend class InterpState;
   friend struct InitMap;
   friend class DynamicAllocator;
+  friend class Program;
 
   /// Returns the embedded descriptor preceding a field.
   InlineDescriptor *getInlineDesc() const {
diff --git a/clang/lib/AST/ByteCode/Program.cpp b/clang/lib/AST/ByteCode/Program.cpp
index 749ae2510612c..af65272819351 100644
--- a/clang/lib/AST/ByteCode/Program.cpp
+++ b/clang/lib/AST/ByteCode/Program.cpp
@@ -213,19 +213,29 @@ std::optional<unsigned> Program::createGlobal(const ValueDecl *VD,
 
   // Register all previous declarations as well. For extern blocks, just replace
   // the index with the new variable.
-  if (auto Idx =
-          createGlobal(VD, VD->getType(), IsStatic, IsExtern, IsWeak, Init)) {
-    for (const Decl *P = VD; P; P = P->getPreviousDecl()) {
-      unsigned &PIdx = GlobalIndices[P];
-      if (P != VD) {
-        if (Globals[PIdx]->block()->isExtern())
-          Globals[PIdx] = Globals[*Idx];
+  std::optional<unsigned> Idx =
+      createGlobal(VD, VD->getType(), IsStatic, IsExtern, IsWeak, Init);
+  if (!Idx)
+    return std::nullopt;
+
+  Global *NewGlobal = Globals[*Idx];
+  for (const Decl *Redecl : VD->redecls()) {
+    unsigned &PIdx = GlobalIndices[Redecl];
+    if (Redecl != VD) {
+      Block *RedeclBlock = Globals[PIdx]->block();
+      if (RedeclBlock->isExtern()) {
+        Globals[PIdx] = NewGlobal;
+        // All pointers pointing to the previous extern decl now point to the
+        // new decl.
+        for (Pointer *Ptr = RedeclBlock->Pointers; Ptr;
+             Ptr = Ptr->PointeeStorage.BS.Next)
+          Ptr->PointeeStorage.BS.Pointee = NewGlobal->block();
       }
-      PIdx = *Idx;
     }
-    return *Idx;
+    PIdx = *Idx;
   }
-  return std::nullopt;
+
+  return *Idx;
 }
 
 std::optional<unsigned> Program::createGlobal(const Expr *E) {
@@ -264,7 +274,7 @@ std::optional<unsigned> Program::createGlobal(const DeclTy &D, QualType Ty,
       Ctx.getEvalID(), getCurrentDecl(), Desc, IsStatic, IsExtern, IsWeak);
   G->block()->invokeCtor();
 
-  // Initialize InlineDescriptor fields.
+  // Initialize GlobalInlineDescriptor fields.
   auto *GD = new (G->block()->rawData()) GlobalInlineDescriptor();
   if (!Init)
     GD->InitState = GlobalInitState::NoInitializer;
diff --git a/clang/test/AST/ByteCode/literals.cpp b/clang/test/AST/ByteCode/literals.cpp
index ddf1d2bebdbd0..54544464c28ea 100644
--- a/clang/test/AST/ByteCode/literals.cpp
+++ b/clang/test/AST/ByteCode/literals.cpp
@@ -1430,3 +1430,10 @@ namespace OnePastEndCmp {
   constexpr const int *q = &s.a + 1;
   static_assert(p != q, "");
 }
+
+namespace ExternRedecl {
+  extern const int a;
+  constexpr const int *p = &a;
+  constexpr int a = 10;
+  static_assert(*p == 10);
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/154273