From 36c4344ddf1866005c62910166ca077bf2e8f62e Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Wed, 26 Aug 2026 17:38:21 +0800
Subject: [CodeGen] Implement RISC-V finalize-isel

---
 backend/lib/CodeGen/CMakeLists.txt   |   2 +
 backend/lib/CodeGen/FinalizeISel.cpp | 101 +++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 backend/lib/CodeGen/FinalizeISel.cpp

(limited to 'backend/lib/CodeGen')

diff --git a/backend/lib/CodeGen/CMakeLists.txt b/backend/lib/CodeGen/CMakeLists.txt
index 795fb40..a7a0586 100644
--- a/backend/lib/CodeGen/CMakeLists.txt
+++ b/backend/lib/CodeGen/CMakeLists.txt
@@ -8,6 +8,7 @@ set(
   GlobalObject.cpp
   GenericOpcodes.cpp
   FrameIndexElimination.cpp
+  FinalizeISel.cpp
   InstructionDescriptor.cpp
   LowLevelType.cpp
   MachineBasicBlockAttributes.cpp
@@ -100,6 +101,7 @@ set(
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/GlobalObject.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/GenericOpcodes.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/FrameIndexElimination.h"
+  "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/FinalizeISel.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/InstructionDescriptor.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/InlineAsm.h"
   "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/LowLevelType.h"
diff --git a/backend/lib/CodeGen/FinalizeISel.cpp b/backend/lib/CodeGen/FinalizeISel.cpp
new file mode 100644
index 0000000..9b5c11f
--- /dev/null
+++ b/backend/lib/CodeGen/FinalizeISel.cpp
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/FinalizeISel.h"
+
+#include "rcc/CodeGen/InstructionDescriptor.h"
+#include "rcc/CodeGen/MachineBasicBlock.h"
+#include "rcc/CodeGen/MachineFrameInfo.h"
+#include "rcc/CodeGen/MachineFunction.h"
+#include "rcc/CodeGen/MachineInstr.h"
+#include "rcc/CodeGen/TargetDescription.h"
+
+#include <utility>
+
+namespace rcc {
+namespace {
+
+[[nodiscard]] const MachinePassContract &finalizeISelContract() {
+  static const MachinePassContract Contract = [] {
+    MachinePassContract Value{
+        .Name = "finalize-isel",
+        .Requires = {},
+        .Sets = {},
+        .Clears = {},
+        .RequiredAnalyses = {},
+        .VerificationStage = PipelineStage::Selected,
+    };
+    Value.ThreadSafety = PassThreadSafety::ThreadSafe;
+    Value.DeclaredChanges = {MachinePassChange::Instructions, MachinePassChange::Operands,
+                             MachinePassChange::CFG, MachinePassChange::BlockLayout,
+                             MachinePassChange::Frame};
+    return Value;
+  }();
+  return Contract;
+}
+
+} // namespace
+
+const MachinePassContract &FinalizeISelPass::contract() const noexcept {
+  return finalizeISelContract();
+}
+
+Expected<MachinePassResult> FinalizeISelPass::run(MachineFunction &Function,
+                                                  const TargetDescription &Target,
+                                                  MachineFunctionAnalysisManager &) {
+  MachinePassResult Result;
+  MachineBasicBlock *Block = Function.firstBlock();
+  while (Block != nullptr) {
+    MachineInstr *Instruction = Block->firstInstruction();
+    while (Instruction != nullptr) {
+      MachineInstr *Next = Instruction->next();
+      const InstructionDescriptor *Descriptor = Target.instructionDescriptor(Instruction->opcode());
+      if (Descriptor == nullptr) {
+        return makeUnexpected(ErrorCode::VerificationError,
+                              "finalize-isel encountered an unknown opcode");
+      }
+
+      if (Instruction->flags().has(MachineInstrFlag::FrameSetup) ||
+          Instruction->flags().has(MachineInstrFlag::FrameDestroy)) {
+        MachineFrameState State = Function.frameInfo().state();
+        if (!State.AdjustsStack) {
+          State.AdjustsStack = true;
+          auto Updated = Function.frameInfo().setState(std::move(State));
+          if (!Updated)
+            return std::unexpected(Updated.error());
+          Result.Changes.add(MachinePassChange::Frame);
+        }
+      }
+
+      if (!Descriptor->Flags.has(InstructionFlag::UsesCustomInserter)) {
+        Instruction = Next;
+        continue;
+      }
+
+      auto Expanded = Info->emitInstrWithCustomInserter(*Instruction, *Block, Function, Target);
+      if (!Expanded)
+        return std::unexpected(Expanded.error());
+      if (*Expanded == nullptr || &(*Expanded)->function() != &Function) {
+        return makeUnexpected(ErrorCode::InternalError,
+                              "custom inserter returned an invalid basic block");
+      }
+
+      Result.Changes.add(MachinePassChange::Instructions);
+      Result.Changes.add(MachinePassChange::Operands);
+      if (*Expanded != Block) {
+        Result.Changes.add(MachinePassChange::CFG);
+        Result.Changes.add(MachinePassChange::BlockLayout);
+        Block = *Expanded;
+        Instruction = Block->firstInstruction();
+      } else {
+        Instruction = Next;
+      }
+    }
+    Block = Block->next();
+  }
+
+  Result.Changed = !Result.Changes.empty();
+  Result.Preserved = Result.Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
+  return Result;
+}
+
+} // namespace rcc
-- 
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