Revert "[lldb] Remove "dwarf dynamic register size expressions" from RegisterInfo"

This reverts commit 00e704b.

This commit should should have updated
llvm/llvm-project/lldb/source/Plugins/ABI/ARC/ABISysV_arc.cpp like the other
architectures.

Author: MForster

lldb/include/lldb/Target/DynamicRegisterInfo.h

@@ -108,6 +108,7 @@ class DynamicRegisterInfo {
   name_collection m_set_names;
   reg_to_regs_map m_value_regs_map;
   reg_to_regs_map m_invalidate_regs_map;
+  dynamic_reg_size_map m_dynamic_reg_size_map;
   size_t m_reg_data_byte_size = 0u; // The number of bytes required to store
                                     // all registers
   bool m_finalized = false;

lldb/include/lldb/Target/RegisterContext.h

@@ -31,6 +31,10 @@ class RegisterContext : public std::enable_shared_from_this<RegisterContext>,
 
   virtual const RegisterInfo *GetRegisterInfoAtIndex(size_t reg) = 0;
 
+  // Detect the register size dynamically.
+  uint32_t UpdateDynamicRegisterSize(const lldb_private::ArchSpec &arch,
+                                     RegisterInfo *reg_info);
+
   virtual size_t GetRegisterSetCount() = 0;
 
   virtual const RegisterSet *GetRegisterSet(size_t reg_set) = 0;

lldb/include/lldb/lldb-private-types.h

@@ -58,6 +58,12 @@ struct RegisterInfo {
   /// this register changes. For example, the invalidate list for eax would be
   /// rax ax, ah, and al.
   uint32_t *invalidate_regs;
+  /// A DWARF expression that when evaluated gives the byte size of this
+  /// register.
+  const uint8_t *dynamic_size_dwarf_expr_bytes;
+  /// The length of the DWARF expression in bytes in the
+  /// dynamic_size_dwarf_expr_bytes member.
+  size_t dynamic_size_dwarf_len;
 
   llvm::ArrayRef<uint8_t> data(const uint8_t *context_base) const {
     return llvm::ArrayRef<uint8_t>(context_base + byte_offset, byte_size);