[NFC][hlsl][Sema] Simplify CBuffer Legacy Size Calculation Control Flow (#127921)

NFC: Small refactor to `calculateLegacyCbufferSize()`'s control flow to
make each branch easier to flow/more visually distinct from each other

Author: V-FEXrt

clang/lib/Sema/SemaHLSL.cpp

@@ -176,9 +176,9 @@ Decl *SemaHLSL::ActOnStartBuffer(Scope *BufferScope, bool CBuffer,
 // https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-packing-rules
 static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
                                            QualType T) {
-  unsigned Size = 0;
   constexpr unsigned CBufferAlign = 16;
   if (const RecordType *RT = T->getAs<RecordType>()) {
+    unsigned Size = 0;
     const RecordDecl *RD = RT->getDecl();
     for (const FieldDecl *Field : RD->fields()) {
       QualType Ty = Field->getType();
@@ -191,22 +191,28 @@ static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
       Size = llvm::alignTo(Size, FieldAlign);
       Size += FieldSize;
     }
-  } else if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
-    if (unsigned ElementCount = AT->getSize().getZExtValue()) {
-      unsigned ElementSize =
-          calculateLegacyCbufferSize(Context, AT->getElementType());
-      unsigned AlignedElementSize = llvm::alignTo(ElementSize, CBufferAlign);
-      Size = AlignedElementSize * (ElementCount - 1) + ElementSize;
-    }
-  } else if (const VectorType *VT = T->getAs<VectorType>()) {
+    return Size;
+  }
+
+  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) {
+    unsigned ElementCount = AT->getSize().getZExtValue();
+    if (ElementCount == 0)
+      return 0;
+
+    unsigned ElementSize =
+        calculateLegacyCbufferSize(Context, AT->getElementType());
+    unsigned AlignedElementSize = llvm::alignTo(ElementSize, CBufferAlign);
+    return AlignedElementSize * (ElementCount - 1) + ElementSize;
+  }
+
+  if (const VectorType *VT = T->getAs<VectorType>()) {
     unsigned ElementCount = VT->getNumElements();
     unsigned ElementSize =
         calculateLegacyCbufferSize(Context, VT->getElementType());
-    Size = ElementSize * ElementCount;
-  } else {
-    Size = Context.getTypeSize(T) / 8;
+    return ElementSize * ElementCount;
   }
-  return Size;
+
+  return Context.getTypeSize(T) / 8;
 }
 
 // Validate packoffset: