[clang] [Clang][Sema] placement new initializes typedef array with correct size (PR #83124)

[via cfe-commits]

https://github.com/mahtohappy updated https://github.com/llvm/llvm-project/pull/83124

>From 7f6bbd2a9e5ab162b0efb5c6dcca91e1d83a0bce Mon Sep 17 00:00:00 2001
From: mahtohappy <Happy.Kumar at windriver.com>
Date: Tue, 27 Feb 2024 03:13:51 -0800
Subject: [PATCH] [Clang][Sema] placement new initializes typedef array with
 correct size

---
 clang/lib/Sema/TreeTransform.h                | 14 +++++++++++++-
 .../X86/instantiate-new-placement-size.cpp    | 19 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/X86/instantiate-new-placement-size.cpp

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 7389a48fe56fcc..0cda78650fcc83 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -12669,6 +12669,19 @@ TreeTransform<Derived>::TransformCXXNewExpr(CXXNewExpr *E) {
     ArraySize = NewArraySize.get();
   }
 
+  // Per C++0x [expr.new]p5, the type being constructed may be a
+  // typedef of an array type.
+  QualType AllocType = AllocTypeInfo->getType();
+  if (ArraySize) {
+    if (const ConstantArrayType *Array =
+            SemaRef.Context.getAsConstantArrayType(AllocType)) {
+      ArraySize = IntegerLiteral::Create(SemaRef.Context, Array->getSize(),
+                                         SemaRef.Context.getSizeType(),
+                                         E->getBeginLoc());
+      AllocType = Array->getElementType();
+    }
+  }
+
   // Transform the placement arguments (if any).
   bool ArgumentChanged = false;
   SmallVector<Expr*, 8> PlacementArgs;
@@ -12730,7 +12743,6 @@ TreeTransform<Derived>::TransformCXXNewExpr(CXXNewExpr *E) {
     return E;
   }
 
-  QualType AllocType = AllocTypeInfo->getType();
   if (!ArraySize) {
     // If no array size was specified, but the new expression was
     // instantiated with an array type (e.g., "new T" where T is
diff --git a/clang/test/CodeGen/X86/instantiate-new-placement-size.cpp b/clang/test/CodeGen/X86/instantiate-new-placement-size.cpp
new file mode 100644
index 00000000000000..042554272a9bf6
--- /dev/null
+++ b/clang/test/CodeGen/X86/instantiate-new-placement-size.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang -S -Xclang -triple=x86_64-unknown-linux-gnu -fno-discard-value-names -emit-llvm -o - %s | FileCheck %s
+#include <new>
+
+// CHECK: call void @llvm.memset.p0.i64(ptr align 1 %x, i8 0, i64 8, i1 false)
+// CHECK: call void @llvm.memset.p0.i64(ptr align 16 %x, i8 0, i64 32, i1 false)
+template <typename TYPE>
+void f()
+{
+    typedef TYPE TArray[8];
+
+    TArray x;
+    new(&x) TArray();
+}
+
+int main()
+{
+    f<char>();
+    f<int>();
+}