Address some review feedback

Author: mmha

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -2252,6 +2252,14 @@ def CIR_ArrayCtor : CIR_ArrayInitDestroy<"array.ctor"> {
     Initialize each array element using the same C++ constructor. This
     operation has one region, with one single block. The block has an
     incoming argument for the current array index to initialize.
+
+    ```mlir
+    cir.array.ctor(%0 : !cir.ptr<!cir.array<!rec_S x 42>>) {
+      ^bb0(%arg0: !cir.ptr<!rec_S>):
+        cir.call @_ZN1SC1Ev(%arg0) : (!cir.ptr<!rec_S>) -> ()
+        cir.yield
+    }
+    ```
   }];
 }
 

clang/include/clang/CIR/MissingFeatures.h

@@ -255,6 +255,7 @@ struct MissingFeatures {
   static bool completeDtors() { return false; }
   static bool vtableInitialization() { return false; }
   static bool msvcBuiltins() { return false; }
+  static bool vlas() { return false; }
 
   // Missing types
   static bool dataMemberType() { return false; }

clang/lib/CIR/CodeGen/CIRGenClass.cpp

@@ -355,8 +355,8 @@ void CIRGenFunction::emitCXXAggrConstructorCall(
     // Just skip out if the constant count is zero.
     if (constIntAttr && constIntAttr.getUInt() == 0)
       return;
-    // Otherwise, emit the check.
   } else {
+    // Otherwise, emit the check.
     cgm.errorNYI(e->getSourceRange(), "dynamic-length array expression");
   }
 
@@ -399,7 +399,8 @@ void CIRGenFunction::emitCXXAggrConstructorCall(
     }
 
     // Emit the constructor call that will execute for every array element.
-    mlir::Value arrayOp = builder.createPtrBitcast(arrayBase.getPointer(), arrayTy);
+    mlir::Value arrayOp =
+        builder.createPtrBitcast(arrayBase.getPointer(), arrayTy);
     builder.create<cir::ArrayCtor>(
         *currSrcLoc, arrayOp, [&](mlir::OpBuilder &b, mlir::Location loc) {
           auto arg = b.getInsertionBlock()->addArgument(ptrToElmType, loc);

clang/lib/CIR/CodeGen/CIRGenFunction.cpp

@@ -815,6 +815,7 @@ CIRGenFunction::emitArrayLength(const clang::ArrayType *origArrayType,
   // If it's a VLA, we have to load the stored size.  Note that
   // this is the size of the VLA in bytes, not its size in elements.
   if (isa<VariableArrayType>(arrayType)) {
+    assert(cir::MissingFeatures::vlas());
     cgm.errorNYI(*currSrcLoc, "VLAs");
     return builder.getConstInt(*currSrcLoc, SizeTy, 0);
   }

clang/lib/CIR/Dialect/Transforms/LoweringPrepare.cpp

@@ -12,6 +12,7 @@
 #include "clang/CIR/Dialect/Builder/CIRBaseBuilder.h"
 #include "clang/CIR/Dialect/IR/CIRDialect.h"
 #include "clang/CIR/Dialect/Passes.h"
+#include "clang/CIR/MissingFeatures.h"
 
 #include <memory>
 
@@ -109,6 +110,7 @@ void LoweringPreparePass::lowerArrayCtor(cir::ArrayCtor op) {
   builder.setInsertionPointAfter(op.getOperation());
 
   mlir::Type eltTy = op->getRegion(0).getArgument(0).getType();
+  assert(!cir::MissingFeatures::vlas());
   auto arrayLen =
       mlir::cast<cir::ArrayType>(op.getAddr().getType().getPointee()).getSize();
   lowerArrayDtorCtorIntoLoop(builder, astCtx, op, eltTy, op.getAddr(),

clang/test/CIR/CodeGen/array-ctor.cpp

@@ -68,3 +68,11 @@ void foo() {
 // OGCG: br i1 %[[DONE]], label %[[EXIT:.*]], label %[[LOOP]]
 // OGCG: [[EXIT]]:
 // OGCG: ret void
+
+void zero_sized() {
+    int s[0];
+}
+
+// CIR:     cir.func dso_local @_Z10zero_sizedv()
+// CIR-NOT:   cir.do
+// CIR:       cir.return