[CodeGen] Complete register allocation infrastructure

1 files changed, 94 insertions, 0 deletions

diff --git a/backend/unittests/CodeGen/SpillerTest.cpp b/backend/unittests/CodeGen/SpillerTest.cpp
new file mode 100644
index 0000000..1f22d8f
--- /dev/null
+++ b/backend/unittests/CodeGen/SpillerTest.cpp
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/Spiller.h"
+
+#include "CodeGen/RegisterAllocationTestSupport.h"
+
+#include <iostream>
+#include <optional>
+
+namespace {
+
+using namespace rcc;
+using namespace rcc::test;
+using namespace rcc::test::ra;
+
+void testRematerialization(TestContext &Context, const TargetDescription &Target) {
+  auto Fixture = createFunction("spiller-remat", 20);
+  if (!Fixture)
+    return;
+  auto Value = createVReg(*Fixture->Function);
+  if (!Value || !buildDef(*Fixture->Function, Target, *Fixture->Block, *Value, 42, {}, true) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value))
+    return;
+  VirtRegMap Mapping(*Fixture->Function);
+  TestRegisterAllocationInfo Info;
+  if (!Mapping.add(*Value))
+    return;
+  Spiller ValueSpiller(*Fixture->Function, Target, Info, Mapping, true);
+  auto Children = ValueSpiller.spill(*Value);
+  Context.expect(Children && Children->size() == 2 &&
+                     Fixture->Function->frameInfo().liveObjectCount() == 0 &&
+                     countOpcode(*Fixture->Function, testOpcode(RematerializableDefOpcode)) == 2 &&
+                     countOpcode(*Fixture->Function, testOpcode(SpillLoadOpcode)) == 0,
+                 "Spiller must rematerialize each use without allocating a stack slot");
+}
+
+void testDirectSpillAndDebugUse(TestContext &Context, const TargetDescription &Target) {
+  auto Fixture = createFunction("spiller-debug", 21);
+  if (!Fixture)
+    return;
+  auto Value = createVReg(*Fixture->Function);
+  if (!Value || !buildDef(*Fixture->Function, Target, *Fixture->Block, *Value, 7) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value, {}, true) ||
+      !buildUse(*Fixture->Function, Target, *Fixture->Block, *Value))
+    return;
+  VirtRegMap Mapping(*Fixture->Function);
+  TestRegisterAllocationInfo Info;
+  if (!Mapping.add(*Value))
+    return;
+  Spiller ValueSpiller(*Fixture->Function, Target, Info, Mapping, false);
+  auto Children = ValueSpiller.spill(*Value);
+  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;
+  }
+  const std::optional<Register> DebugRegister =
+      DebugOperand == nullptr ? std::nullopt : DebugOperand->registerValue();
+  const bool DebugRegisterCleared = DebugRegister && DebugRegister.value().isNoRegister();
+  Context.expect(Children && !Children->empty() &&
+                     countOpcode(*Fixture->Function, testOpcode(SpillLoadOpcode)) != 0 &&
+                     countOpcode(*Fixture->Function, testOpcode(SpillStoreOpcode)) != 0 &&
+                     DebugOperand != nullptr && DebugRegisterCleared &&
+                     DebugOperand->registerFlags().has(RegisterOperandFlag::Undef),
+                 "Spiller must preserve direct spill code and clear debug-only uses");
+
+  auto Unspillable = createVReg(*Fixture->Function);
+  if (!Unspillable || !Mapping.add(*Unspillable, false))
+    return;
+  auto Rejected = ValueSpiller.spill(*Unspillable);
+  Context.expect(!Rejected && Rejected.error().code() == ErrorCode::RegisterAllocationFailed,
+                 "Spiller must reject an explicitly non-spillable value");
+}
+
+} // namespace
+
+int main() {
+  TestContext Context;
+  auto Target = createTarget();
+  Context.expect(Target.has_value(), "Spiller test target must be constructible");
+  if (!Target)
+    return Context.result();
+  testRematerialization(Context, *Target);
+  testDirectSpillAndDebugUse(Context, *Target);
+  return Context.result();
+}