[PATCH] D132111: [clang][Interp] Implement pointer (de)ref operations and DeclRefExprs

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 453610.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132111/new/

https://reviews.llvm.org/D132111

Files:
  clang/lib/AST/Interp/ByteCodeExprGen.cpp
  clang/lib/AST/Interp/ByteCodeExprGen.h
  clang/test/AST/Interp/cxx20.cpp
  clang/test/AST/Interp/literals.cpp


Index: clang/test/AST/Interp/literals.cpp
===================================================================
--- clang/test/AST/Interp/literals.cpp
+++ clang/test/AST/Interp/literals.cpp
@@ -32,3 +32,12 @@
 static_assert(!0, "");
 static_assert(-true, "");
 static_assert(-false, ""); //expected-error{{failed}}
+
+constexpr int m = 10;
+constexpr const int *p = &m;
+static_assert(p != nullptr, "");
+static_assert(*p == 10, "");
+
+constexpr const int* getIntPointer() {
+  return &m;
+}
Index: clang/test/AST/Interp/cxx20.cpp
===================================================================
--- /dev/null
+++ clang/test/AST/Interp/cxx20.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -std=c++20 -verify %s
+// RUN: %clang_cc1 -std=c++20 -verify %s -DREFERENCE
+
+
+// expected-no-diagnostics
+constexpr int getMinus5() {
+  int a = 10;
+  a = -5;
+  int *p = &a;
+  return *p;
+}
+
+constexpr int pointerAssign() {
+  int m = 10;
+  int *p = &m;
+
+  *p = 12; // modifies m
+
+  return m;
+}
+//static_assert(pointerAssign() == 12, "");  TODO
+
+constexpr int pointerDeref() {
+  int m = 12;
+  int *p = &m;
+
+  return *p;
+}
+//static_assert(pointerDeref() == 12, ""); TODO
Index: clang/lib/AST/Interp/ByteCodeExprGen.h
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.h
+++ clang/lib/AST/Interp/ByteCodeExprGen.h
@@ -72,6 +72,7 @@
   bool VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E);
   bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E);
   bool VisitUnaryOperator(const UnaryOperator *E);
+  bool VisitDeclRefExpr(const DeclRefExpr *E);
 
 protected:
   bool visitExpr(const Expr *E) override;
Index: clang/lib/AST/Interp/ByteCodeExprGen.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -103,6 +103,7 @@
           if (!this->emitLoadPop(T, CE))
             return false;
           return DiscardResult ? this->emitPop(T, CE) : true;
+          return true;
         });
   }
 
@@ -209,6 +210,12 @@
       return Discard(this->emitAdd(*T, BO));
     case BO_Mul:
       return Discard(this->emitMul(*T, BO));
+    case BO_Assign:
+      if (!this->emitStore(*T, BO))
+        return false;
+      // TODO: Assignments return the assigned value, so the pop() here
+      //   should proably just go away.
+      return this->emitPopPtr(BO);
     default:
       return this->bail(BO);
     }
@@ -596,8 +603,7 @@
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
-  if (!this->Visit(E->getSubExpr()))
-    return false;
+  const Expr *SubExpr = E->getSubExpr();
 
   switch (E->getOpcode()) {
   case UO_PostInc: // x++
@@ -607,16 +613,32 @@
     return false;
 
   case UO_LNot: // !x
+    if (!this->Visit(SubExpr))
+      return false;
     return this->emitInvBool(E);
   case UO_Minus: // -x
+    if (!this->Visit(SubExpr))
+      return false;
     if (Optional<PrimType> T = classify(E->getType()))
       return this->emitNeg(*T, E);
     return false;
   case UO_Plus:  // +x
-    return true; // noop
+    return this->Visit(SubExpr); // noop
 
   case UO_AddrOf: // &x
+    // We should already have a pointer when we get here.
+    return this->Visit(SubExpr);
+
   case UO_Deref:  // *x
+    return dereference(
+        SubExpr, DerefKind::Read,
+        [](PrimType) {
+          llvm_unreachable("Dereferencing requires a pointer");
+          return false;
+        },
+        [this, E](PrimType T) {
+          return DiscardResult ? this->emitPop(T, E) : true;
+        });
   case UO_Not:    // ~x
   case UO_Real:   // __real x
   case UO_Imag:   // __imag x
@@ -628,6 +650,24 @@
   return false;
 }
 
+template <class Emitter>
+bool ByteCodeExprGen<Emitter>::VisitDeclRefExpr(const DeclRefExpr *E) {
+  if (auto It = Locals.find(E->getDecl()); It != Locals.end()) {
+    const unsigned Offset = It->second.Offset;
+    return this->emitGetPtrLocal(Offset, E);
+  } else if (auto GlobalIndex = P.getGlobal(E->getDecl())) {
+    return this->emitGetPtrGlobal(*GlobalIndex, E);
+  } else if (isa<ParmVarDecl>(E->getDecl())) {
+    // I'm pretty sure we should do something here, BUT
+    // when we're in evaluateAsRValue(), we don't have any parameters,
+    // so we can't actually use this->Params. This happens when
+    // a parameter is used in a return statement.
+    return false;
+  }
+
+  return false;
+}
+
 template <class Emitter>
 void ByteCodeExprGen<Emitter>::emitCleanup() {
   for (VariableScope<Emitter> *C = VarScope; C; C = C->getParent())

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