[CodeGen] Add core machine type primitives

Introduce an independent 64-bit extended LLT representation that preserves exact floating-point semantics and supports fixed and scalable vectors. Add opaque physical and virtual registers, strongly typed monotonic stable IDs, and atomic MachineFunctionProperties transitions.

Export the primitives through RCCBackend::CodeGen, cover their boundary and failure cases, record the frozen invariants, and normalize the architecture document permissions.

1 files changed, 56 insertions, 0 deletions

diff --git a/backend/lib/CodeGen/Register.cpp b/backend/lib/CodeGen/Register.cpp
new file mode 100644
index 0000000..0af26c7
--- /dev/null
+++ b/backend/lib/CodeGen/Register.cpp
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/Register.h"
+
+#include <string>
+
+namespace rcc {
+namespace {
+
+constexpr std::uint64_t MaximumRegisterIndex = (std::uint64_t{1} << 31) - 1;
+
+} // namespace
+
+Expected<PhysicalRegister> PhysicalRegister::create(std::uint64_t Number) {
+  if (Number == 0 || Number > MaximumRegisterIndex) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "physical register number must be in the range [1, 2147483647]");
+  }
+  return PhysicalRegister(static_cast<std::uint32_t>(Number));
+}
+
+Expected<Register> Register::makePhysical(std::uint64_t Number) {
+  auto PhysReg = PhysicalRegister::create(Number);
+  if (!PhysReg)
+    return std::unexpected(PhysReg.error());
+  return fromPhysical(*PhysReg);
+}
+
+Expected<Register> Register::makeVirtual(std::uint64_t Index) {
+  if (Index > MaximumRegisterIndex) {
+    return makeUnexpected(ErrorCode::InvalidArgument, "virtual register index must fit in 31 bits");
+  }
+  return Register(VirtualBit | static_cast<std::uint32_t>(Index));
+}
+
+std::optional<PhysicalRegister> Register::physicalRegister() const noexcept {
+  if (!isPhysical())
+    return std::nullopt;
+  return PhysicalRegister(OpaqueValue);
+}
+
+std::optional<std::uint32_t> Register::virtualIndex() const noexcept {
+  if (!isVirtual())
+    return std::nullopt;
+  return OpaqueValue & IndexMask;
+}
+
+std::string Register::toString() const {
+  if (isNoRegister())
+    return "noreg";
+  if (isVirtual())
+    return "%" + std::to_string(OpaqueValue & IndexMask);
+  return "$physreg" + std::to_string(OpaqueValue);
+}
+
+} // namespace rcc