Add semantic::Struct::SizeNoPadding

This is the size of the structure without the trailing alignment
padding. This is what the Dawn needs from the Inspector.

Fixed: tint:653
Change-Id: Iaa01ba949e114973e4a33e084fc10ef9e111016c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/45120
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/semantic/sem_struct.cc

@@ -23,8 +23,13 @@ namespace semantic {
 Struct::Struct(type::Struct* type,
                StructMemberList members,
                uint32_t align,
-               uint32_t size)
-    : type_(type), members_(std::move(members)), align_(align), size_(size) {}
+               uint32_t size,
+               uint32_t size_no_padding)
+    : type_(type),
+      members_(std::move(members)),
+      align_(align),
+      size_(size),
+      size_no_padding_(size_no_padding) {}
 
 Struct::~Struct() = default;
 

src/semantic/struct.h

@@ -46,10 +46,13 @@ class Struct : public Castable<Struct, Node> {
   /// @param members the structure members
   /// @param align the byte alignment of the structure
   /// @param size the byte size of the structure
+  /// @param size_no_padding size of the members without the end of structure
+  /// alignment padding
   Struct(type::Struct* type,
          StructMemberList members,
          uint32_t align,
-         uint32_t size);
+         uint32_t size,
+         uint32_t size_no_padding);
 
   /// Destructor
   ~Struct() override;
@@ -72,11 +75,16 @@ class Struct : public Castable<Struct, Node> {
   /// decoration.
   uint32_t Size() const { return size_; }
 
+  /// @returns the byte size of the members without the end of structure
+  /// alignment padding
+  uint32_t SizeNoPadding() const { return size_no_padding_; }
+
  private:
   type::Struct* const type_;
   StructMemberList const members_;
   uint32_t const align_;
   uint32_t const size_;
+  uint32_t const size_no_padding_;
 };
 
 /// StructMember holds the semantic information for structure members.