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/unittests/CodeGen/RegAllocFastTest.cpp | 83 ++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 backend/unittests/CodeGen/RegAllocFastTest.cpp

(limited to 'backend/unittests/CodeGen/RegAllocFastTest.cpp')

diff --git a/backend/unittests/CodeGen/RegAllocFastTest.cpp b/backend/unittests/CodeGen/RegAllocFastTest.cpp
new file mode 100644
index 0000000..cf5498f
--- /dev/null
+++ b/backend/unittests/CodeGen/RegAllocFastTest.cpp
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "CodeGen/RegisterAllocationTestSupport.h"
+#include "rcc/CodeGen/MachineCFGUpdater.h"
+
+#include <iostream>
+
+namespace {
+
+using namespace rcc;
+using namespace rcc::test;
+using namespace rcc::test::ra;
+
+void testBlockBoundary(TestContext &Context, const TargetDescription &Target) {
+  auto Fixture = createFunction("fast-boundary", 40);
+  if (!Fixture)
+    return;
+  auto Exit = Fixture->Function->createBasicBlock();
+  if (!Exit || !Fixture->Function->appendBlock(**Exit) ||
+      !Fixture->Function->cfgUpdater().addSuccessor(*Fixture->Block, **Exit,
+                                                    BranchProbability::one()))
+    return;
+  auto Value = createVReg(*Fixture->Function);
+  if (!Value || !buildDef(*Fixture->Function, Target, *Fixture->Block, *Value, 9) ||
+      !buildUse(*Fixture->Function, Target, **Exit, *Value) ||
+      !buildUse(*Fixture->Function, Target, **Exit,
+                Register::fromPhysical(physical(TestRegister::G0))) ||
+      !prepareForAllocation(*Fixture->Function, Target))
+    return;
+  TestRegisterAllocationInfo Info;
+  auto Allocated = runAllocator(*Fixture->Function, Target, Info, AllocatorKind::Fast);
+  Context.expect(Allocated && countOpcode(*Fixture->Function, testOpcode(SpillStoreOpcode)) == 1 &&
+                     countOpcode(*Fixture->Function, testOpcode(SpillLoadOpcode)) == 1 &&
+                     Fixture->Function->properties().has(MachineFunctionProperty::NoVRegs),
+                 "FastAllocator must preserve values across a block boundary");
+}
+
+void testFunctionLiveInAndDebug(TestContext &Context, const TargetDescription &Target) {
+  auto Fixture = createFunction("fast-live-in", 41);
+  if (!Fixture)
+    return;
+  auto Value = createVReg(*Fixture->Function);
+  const PhysicalRegister G0 = physical(TestRegister::G0);
+  if (!Value || !Fixture->Function->registerInfo().addLiveIn(G0, *Value) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value, {}, true) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value) ||
+      !prepareForAllocation(*Fixture->Function, Target))
+    return;
+  TestRegisterAllocationInfo Info;
+  auto Allocated = runAllocator(*Fixture->Function, Target, Info, AllocatorKind::Fast);
+  const MachineOperand *DebugOperand = nullptr;
+  for (const MachineInstr *Instruction = Fixture->Block->firstInstruction(); Instruction != nullptr;
+       Instruction = Instruction->next()) {
+    for (const MachineOperand &Operand : Instruction->operands()) {
+      if (Operand.isDebugUse()) {
+        DebugOperand = &Operand;
+        break;
+      }
+    }
+    if (DebugOperand != nullptr)
+      break;
+  }
+  Context.expect(
+      Allocated && DebugOperand != nullptr && DebugOperand->registerValue() &&
+          (DebugOperand->registerValue()->isNoRegister() ||
+           DebugOperand->registerValue() == Register::fromPhysical(G0)) &&
+          std::ranges::none_of(Fixture->Function->registerInfo().virtualRegisters(),
+                               [](const VirtualRegisterInfo &Info) { return !Info.IsTombstone; }),
+      "FastAllocator must preserve function live-ins and debug locations");
+}
+
+} // namespace
+
+int main() {
+  TestContext Context;
+  auto Target = createTarget();
+  Context.expect(Target.has_value(), "FastAllocator test target must be constructible");
+  if (!Target)
+    return Context.result();
+  testBlockBoundary(Context, *Target);
+  testFunctionLiveInAndDebug(Context, *Target);
+  return Context.result();
+}
-- 
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