[llvm] [NFC] Refactoring MCDXBC to support out of order storage of root parameters (PR #137284)

[Justin Bogner via llvm-commits]

================
@@ -78,27 +78,31 @@ void RootSignatureDesc::write(raw_ostream &OS) const {
   assert(NumParameters == ParamsOffsets.size());
   for (size_t I = 0; I < NumParameters; ++I) {
     rewriteOffsetToCurrentByte(BOS, ParamsOffsets[I]);
-    const mcdxbc::RootParameter &P = Parameters[I];
-
-    switch (P.Header.ParameterType) {
-    case llvm::to_underlying(dxbc::RootParameterType::Constants32Bit):
-      support::endian::write(BOS, P.Constants.ShaderRegister,
+    const auto &[Type, Loc] = ParametersContainer.getTypeAndLocForParameter(I);
+    switch (Type) {
+    case llvm::to_underlying(dxbc::RootParameterType::Constants32Bit): {
+      const dxbc::RootConstants &Constants =
+          ParametersContainer.getConstant(Loc);
+      support::endian::write(BOS, Constants.ShaderRegister,
                              llvm::endianness::little);
-      support::endian::write(BOS, P.Constants.RegisterSpace,
+      support::endian::write(BOS, Constants.RegisterSpace,
                              llvm::endianness::little);
-      support::endian::write(BOS, P.Constants.Num32BitValues,
+      support::endian::write(BOS, Constants.Num32BitValues,
                              llvm::endianness::little);
-      break;
+    } break;
----------------
bogner wrote:

The break statement should be inside the block here.
```suggestion
      break;
    }
```

https://github.com/llvm/llvm-project/pull/137284