[CodeGen] Implement RV64GC frame lowering

1 files changed, 61 insertions, 0 deletions

diff --git a/backend/lib/CodeGen/FrameIndexElimination.cpp b/backend/lib/CodeGen/FrameIndexElimination.cpp
new file mode 100644
index 0000000..53c64e1
--- /dev/null
+++ b/backend/lib/CodeGen/FrameIndexElimination.cpp
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/FrameIndexElimination.h"
+
+#include "rcc/CodeGen/MachineBasicBlock.h"
+#include "rcc/CodeGen/MachineFunction.h"
+#include "rcc/CodeGen/MachineInstr.h"
+#include "rcc/CodeGen/MachineMemOperand.h"
+#include "rcc/CodeGen/MachineOperand.h"
+#include "rcc/CodeGen/RegisterScavenger.h"
+#include "rcc/CodeGen/TargetFrameLowering.h"
+
+#include <cstddef>
+#include <utility>
+
+namespace rcc {
+
+Expected<bool> eliminateFrameIndices(MachineFunction &Function, const TargetDescription &Target,
+                                     const TargetFrameLowering &FrameLowering,
+                                     RegisterScavenger &Scavenger) {
+  bool Changed = false;
+  for (MachineBasicBlock *Block = Function.firstBlock(); Block != nullptr; Block = Block->next()) {
+    for (MachineInstr *Instruction = Block->firstInstruction(); Instruction != nullptr;) {
+      MachineInstr *Next = Instruction->next();
+      for (std::size_t Index = 0; Index < Instruction->operandCount(); ++Index) {
+        if (Instruction->operandAt(Index)->kind() != MachineOperand::Kind::FrameIndex)
+          continue;
+        auto Eliminated =
+            FrameLowering.eliminateFrameIndex(*Instruction, Index, Function, Target, Scavenger);
+        if (!Eliminated)
+          return std::unexpected(Eliminated.error());
+        Changed = true;
+      }
+
+      for (std::size_t Index = 0; Index < Instruction->memOperands().size(); ++Index) {
+        const MachineMemOperand *Memory = Instruction->memOperands()[Index];
+        const auto Frame = Memory->description().Base.frameIndex();
+        if (!Frame)
+          continue;
+        auto Reference = FrameLowering.getFrameIndexReference(Function, *Instruction, *Frame,
+                                                              Memory->description().Offset);
+        if (!Reference)
+          return std::unexpected(Reference.error());
+        MachineMemOperandDesc Description = Memory->description();
+        Description.Base = MemoryBase::stack();
+        Description.Offset = Reference->Offset;
+        auto Replacement = Function.createMemOperand(std::move(Description));
+        if (!Replacement)
+          return std::unexpected(Replacement.error());
+        auto Replaced = Instruction->replaceMemOperand(Index, **Replacement);
+        if (!Replaced)
+          return std::unexpected(Replaced.error());
+        Changed = true;
+      }
+      Instruction = Next;
+    }
+  }
+  return Changed;
+}
+
+} // namespace rcc