clang: Handle deleting pointers to incomplete array types (#150359)

CodeGenFunction::EmitCXXDeleteExpr contains logic to go from a pointer
to an array to a pointer to the first element of the array using a
getelementptr LLVM IR instruction. This was done for pointers that were
not variable length arrays, as pointers to variable length arrays never
existed in LLVM IR, but rather than checking for arrays that were not
variable length arrays, it checked for arrays that had a constant bound.
This caused incomplete arrays to be inadvertently omitted.

This getelementptr was necessary back when LLVM IR used typed pointers,
but they have been gone for a while, a gep with a constant zero offset
does nothing now, so we can simplify the code by removing that.

1 files changed, 3 insertions, 24 deletions

diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 359e30c..b8238a4 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -2146,30 +2146,9 @@ void CodeGenFunction::EmitCXXDeleteExpr(const CXXDeleteExpr *E) {
     return;
   }
 
-  // We might be deleting a pointer to array.  If so, GEP down to the
-  // first non-array element.
-  // (this assumes that A(*)[3][7] is converted to [3 x [7 x %A]]*)
-  if (DeleteTy->isConstantArrayType()) {
-    llvm::Value *Zero = Builder.getInt32(0);
-    SmallVector<llvm::Value*,8> GEP;
-
-    GEP.push_back(Zero); // point at the outermost array
-
-    // For each layer of array type we're pointing at:
-    while (const ConstantArrayType *Arr
-             = getContext().getAsConstantArrayType(DeleteTy)) {
-      // 1. Unpeel the array type.
-      DeleteTy = Arr->getElementType();
-
-      // 2. GEP to the first element of the array.
-      GEP.push_back(Zero);
-    }
-
-    Ptr = Builder.CreateInBoundsGEP(Ptr, GEP, ConvertTypeForMem(DeleteTy),
-                                    Ptr.getAlignment(), "del.first");
-  }
-
-  assert(ConvertTypeForMem(DeleteTy) == Ptr.getElementType());
+  // We might be deleting a pointer to array.
+  DeleteTy = getContext().getBaseElementType(DeleteTy);
+  Ptr = Ptr.withElementType(ConvertTypeForMem(DeleteTy));
 
   if (E->isArrayForm()) {
     EmitArrayDelete(*this, E, Ptr, DeleteTy);