[clang] [HLSL][NFC] Move packoffset validation to separate function and calculate offsets in bytes (PR #121989)

[Helena Kotas via cfe-commits]

================
@@ -219,33 +223,41 @@ void SemaHLSL::ActOnFinishBuffer(Decl *Dcl, SourceLocation RBrace) {
     }
   }
 
-  if (HasPackOffset && HasNonPackOffset)
-    Diag(BufDecl->getLocation(), diag::warn_hlsl_packoffset_mix);
-
-  if (HasPackOffset) {
-    ASTContext &Context = getASTContext();
-    // Make sure no overlap in packoffset.
-    // Sort PackOffsetVec by offset.
-    std::sort(PackOffsetVec.begin(), PackOffsetVec.end(),
-              [](const std::pair<VarDecl *, HLSLPackOffsetAttr *> &LHS,
-                 const std::pair<VarDecl *, HLSLPackOffsetAttr *> &RHS) {
-                return LHS.second->getOffset() < RHS.second->getOffset();
-              });
-
-    for (unsigned i = 0; i < PackOffsetVec.size() - 1; i++) {
-      VarDecl *Var = PackOffsetVec[i].first;
-      HLSLPackOffsetAttr *Attr = PackOffsetVec[i].second;
-      unsigned Size = calculateLegacyCbufferSize(Context, Var->getType());
-      unsigned Begin = Attr->getOffset() * 32;
-      unsigned End = Begin + Size;
-      unsigned NextBegin = PackOffsetVec[i + 1].second->getOffset() * 32;
-      if (End > NextBegin) {
-        VarDecl *NextVar = PackOffsetVec[i + 1].first;
-        Diag(NextVar->getLocation(), diag::err_hlsl_packoffset_overlap)
-            << NextVar << Var;
-      }
+  if (!HasPackOffset)
+    return;
+
+  if (HasNonPackOffset)
+    S.Diag(BufDecl->getLocation(), diag::warn_hlsl_packoffset_mix);
+
+  // Make sure there is no overlap in packoffset - sort PackOffsetVec by offset
+  // and compare adjacent values.
+  ASTContext &Context = S.getASTContext();
+  std::sort(PackOffsetVec.begin(), PackOffsetVec.end(),
+            [](const std::pair<VarDecl *, HLSLPackOffsetAttr *> &LHS,
+               const std::pair<VarDecl *, HLSLPackOffsetAttr *> &RHS) {
+              return LHS.second->getOffsetInBytes() <
+                     RHS.second->getOffsetInBytes();
+            });
+  for (unsigned i = 0; i < PackOffsetVec.size() - 1; i++) {
+    VarDecl *Var = PackOffsetVec[i].first;
+    HLSLPackOffsetAttr *Attr = PackOffsetVec[i].second;
+    unsigned Size = calculateLegacyCbufferSize(Context, Var->getType());
+    unsigned Begin = Attr->getOffsetInBytes();
----------------
hekota wrote:

See the `Attr.td` comment above.

https://github.com/llvm/llvm-project/pull/121989