From f89d528efc0228c049c2867dcba886a56bac8619 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Fri, 28 Aug 2026 18:51:10 +0800
Subject: [CodeGen] Add target machine registry

---
 backend/lib/MC/CMakeLists.txt     |  4 ++-
 backend/lib/MC/TargetRegistry.cpp | 73 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 backend/lib/MC/TargetRegistry.cpp

(limited to 'backend/lib/MC')

diff --git a/backend/lib/MC/CMakeLists.txt b/backend/lib/MC/CMakeLists.txt
index 330ede3..b314c58 100644
--- a/backend/lib/MC/CMakeLists.txt
+++ b/backend/lib/MC/CMakeLists.txt
@@ -14,6 +14,7 @@ set(
   MCObjectStreamer.cpp
   MCSection.cpp
   MCStreamer.cpp
+  TargetRegistry.cpp
 )
 set(
   RCCBackendMCHeaders
@@ -33,6 +34,7 @@ set(
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/MC/MCSection.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/MC/MCStreamer.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/MC/MCSymbol.h"
+  "${RCC_BACKEND_SOURCE_DIR}/include/rcc/MC/TargetRegistry.h"
 )
 
 add_library(RCCBackendMC ${RCCBackendMCSources})
@@ -46,7 +48,7 @@ target_include_directories(
     "$<BUILD_INTERFACE:${RCC_BACKEND_SOURCE_DIR}/include>"
     "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>"
 )
-target_link_libraries(RCCBackendMC PUBLIC RCCBackend::Support)
+target_link_libraries(RCCBackendMC PUBLIC RCCBackend::Support RCCBackend::Target)
 
 set_target_properties(
   RCCBackendMC
diff --git a/backend/lib/MC/TargetRegistry.cpp b/backend/lib/MC/TargetRegistry.cpp
new file mode 100644
index 0000000..217f59b
--- /dev/null
+++ b/backend/lib/MC/TargetRegistry.cpp
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/MC/TargetRegistry.h"
+
+#include "rcc/Target/TargetMachine.h"
+
+#include <algorithm>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace rcc {
+namespace {
+
+[[nodiscard]] std::vector<const Target *> &registeredTargets() {
+  static std::vector<const Target *> Targets;
+  return Targets;
+}
+
+} // namespace
+
+TargetMachineOptions Target::defaultMachineOptions() const {
+  return DefaultOptions();
+}
+
+Expected<std::unique_ptr<TargetMachine>>
+Target::createTargetMachine(TargetMachineOptions Options) const {
+  return TargetMachineCtor(*this, std::move(Options));
+}
+
+void TargetRegistry::registerTarget(const Target &RegisteredTarget) {
+  std::vector<const Target *> &Targets = registeredTargets();
+  if (std::ranges::find(Targets, &RegisteredTarget) == Targets.end())
+    Targets.push_back(&RegisteredTarget);
+}
+
+Expected<const Target *> TargetRegistry::lookupTarget(std::string_view Triple) {
+  const Target *Best = nullptr;
+  unsigned BestQuality = 0;
+  for (const Target *Candidate : registeredTargets()) {
+    const unsigned Quality = Candidate->matchQuality(Triple);
+    if (Quality > BestQuality) {
+      Best = Candidate;
+      BestQuality = Quality;
+    } else if (Quality != 0 && Quality == BestQuality) {
+      return makeUnexpected(ErrorCode::InvalidInvocation,
+                            "target triple matches multiple registered targets");
+    }
+  }
+  if (Best == nullptr) {
+    return makeUnexpected(ErrorCode::Unsupported,
+                          "no registered target supports triple '" + std::string(Triple) + "'");
+  }
+  return Best;
+}
+
+Expected<const Target *> TargetRegistry::defaultTarget() {
+  const Target *Default = nullptr;
+  for (const Target *Candidate : registeredTargets()) {
+    if (!Candidate->isDefault())
+      continue;
+    if (Default != nullptr) {
+      return makeUnexpected(ErrorCode::InternalError,
+                            "multiple targets are registered as the default target");
+    }
+    Default = Candidate;
+  }
+  if (Default == nullptr)
+    return makeUnexpected(ErrorCode::InternalError, "no default target is registered");
+  return Default;
+}
+
+} // namespace rcc
-- 
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