From e5fdceb9b869f010a2a75638fd38aaf1867f3008 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sun, 9 Aug 2026 04:40:17 +0800
Subject: [CodeGen] Complete register allocation infrastructure

---
 backend/lib/CodeGen/RegAllocBase.cpp | 91 ++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 backend/lib/CodeGen/RegAllocBase.cpp

(limited to 'backend/lib/CodeGen/RegAllocBase.cpp')

diff --git a/backend/lib/CodeGen/RegAllocBase.cpp b/backend/lib/CodeGen/RegAllocBase.cpp
new file mode 100644
index 0000000..1aae22d
--- /dev/null
+++ b/backend/lib/CodeGen/RegAllocBase.cpp
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "RegAllocBase.h"
+
+#include "rcc/CodeGen/MachineLiveness.h"
+#include "rcc/CodeGen/Spiller.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <unordered_set>
+#include <utility>
+
+namespace rcc {
+
+std::vector<const LiveInterval *>
+orderedAllocationIntervals(const LiveIntervalsAnalysis::Result &Intervals,
+                           const MachineFunction &Function) {
+  std::vector<const LiveInterval *> Result;
+  for (std::size_t Index = 0; Index < Function.registerInfo().virtualRegisters().size(); ++Index) {
+    auto Reg = Register::makeVirtual(Index);
+    if (!Reg)
+      continue;
+    const LiveInterval *Interval = Intervals.interval(*Reg);
+    if (Interval != nullptr && !Interval->MainRange.empty())
+      Result.push_back(Interval);
+  }
+  std::ranges::sort(Result, [](const LiveInterval *Left, const LiveInterval *Right) {
+    const LiveSegment &LeftSegment = Left->MainRange.segments().front();
+    const LiveSegment &RightSegment = Right->MainRange.segments().front();
+    if (LeftSegment.Start != RightSegment.Start)
+      return LeftSegment.Start < RightSegment.Start;
+    if (LeftSegment.End != RightSegment.End)
+      return LeftSegment.End < RightSegment.End;
+    return Left->Reg.opaqueValue() < Right->Reg.opaqueValue();
+  });
+  return Result;
+}
+
+Expected<regalloc_detail::AllocationRunResult> RegAllocBase::run() {
+  const std::uint64_t InitialFingerprint = regalloc_detail::allocationFingerprint(Function);
+  const std::size_t InitialFrameObjects = Function.frameInfo().liveObjectCount();
+  VirtRegMap Mapping(Function);
+  auto Initialized = regalloc_detail::initializeMapping(Function, Mapping);
+  if (!Initialized)
+    return std::unexpected(Initialized.error());
+
+  std::unordered_set<std::uint64_t> SeenFingerprints;
+  while (true) {
+    const std::uint64_t Fingerprint = regalloc_detail::allocationFingerprint(Function);
+    if (!SeenFingerprints.insert(Fingerprint).second) {
+      return makeUnexpected(ErrorCode::InternalError,
+                            "register allocation spill/rebuild cycle made no progress");
+    }
+    auto Intervals = Analyses.getResult<LiveIntervalsAnalysis>(Function, Target);
+    if (!Intervals)
+      return std::unexpected(Intervals.error());
+    auto Round = allocateRound(**Intervals, Mapping);
+    if (!Round)
+      return std::unexpected(Round.error());
+    if (Round->Spilled.empty())
+      break;
+
+    std::ranges::sort(Round->Spilled, [](Register Left, Register Right) {
+      return Left.opaqueValue() < Right.opaqueValue();
+    });
+    Spiller ValueSpiller(Function, Target, TargetInfo, Mapping, Options.EnableRematerialization);
+    for (const Register VirtualReg : Round->Spilled) {
+      VirtRegMapEntry *Entry = Mapping.entry(VirtualReg);
+      if (Entry != nullptr) {
+        Entry->PhysicalReg.reset();
+        Entry->State = VirtRegAllocationState::Unassigned;
+      }
+      auto NewRegisters = ValueSpiller.spill(VirtualReg);
+      if (!NewRegisters)
+        return std::unexpected(NewRegisters.error());
+    }
+    Analyses.clear(Function);
+  }
+
+  auto Rewritten = rewriteVirtualRegisters(Function, Target, Mapping);
+  if (!Rewritten)
+    return std::unexpected(Rewritten.error());
+  const std::uint64_t FinalFingerprint = regalloc_detail::allocationFingerprint(Function);
+  regalloc_detail::AllocationRunResult Result;
+  Result.Changed = InitialFingerprint != FinalFingerprint || *Rewritten;
+  Result.ChangedInstructions = InitialFingerprint != FinalFingerprint;
+  Result.ChangedFrame = InitialFrameObjects != Function.frameInfo().liveObjectCount();
+  return Result;
+}
+
+} // namespace rcc
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