[CodeGen] Add MachineFrameInfo

Model stable frame indices, stack object kinds, tombstones, lifetimes, and frozen layouts. Validate owned frame references in the builder and verifier, and remap complete frame state during MachineFunction cloning.

1 files changed, 234 insertions, 0 deletions

diff --git a/backend/lib/CodeGen/MachineFrameInfo.cpp b/backend/lib/CodeGen/MachineFrameInfo.cpp
new file mode 100644
index 0000000..58eab00
--- /dev/null
+++ b/backend/lib/CodeGen/MachineFrameInfo.cpp
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/MachineFrameInfo.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <unordered_set>
+#include <utility>
+
+namespace rcc {
+
+Expected<StackID> StackID::targetStack(std::uint32_t Value) {
+  if (Value < FirstTargetStackValue) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "target stack ID must not overlap a built-in stack ID");
+  }
+  return StackID(Value);
+}
+
+bool StackObject::isSpill() const noexcept {
+  const StackObjectDesc *Desc = description();
+  if (Desc == nullptr)
+    return false;
+  return Desc->Kind == StackObjectKind::SpillSlot || Desc->Kind == StackObjectKind::CalleeSaved ||
+         Desc->Kind == StackObjectKind::EmergencySpill;
+}
+
+bool StackObject::isFixed() const noexcept {
+  const StackObjectDesc *Desc = description();
+  return Desc != nullptr && Desc->Kind == StackObjectKind::FixedABI;
+}
+
+bool StackObject::isVariableSized() const noexcept {
+  const StackObjectDesc *Desc = description();
+  return Desc != nullptr && (Desc->Kind == StackObjectKind::VariableSized ||
+                             Desc->Kind == StackObjectKind::DynamicAlloca);
+}
+
+Expected<void> MachineFrameInfo::verifyDescription(const StackObjectDesc &Description) {
+  if (Description.Kind >= StackObjectKind::Count)
+    return makeUnexpected(ErrorCode::InvalidArgument, "stack object kind is invalid");
+  if (!Description.Stack.isValid())
+    return makeUnexpected(ErrorCode::InvalidArgument, "stack object has an invalid stack ID");
+
+  const bool IsVariable = Description.Kind == StackObjectKind::VariableSized ||
+                          Description.Kind == StackObjectKind::DynamicAlloca;
+  if (IsVariable) {
+    if (Description.Size || Description.Offset) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "variable-sized stack objects cannot have a fixed size or offset");
+    }
+  } else if (!Description.Size || *Description.Size == 0) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "fixed-size stack objects require a nonzero size");
+  }
+
+  if (Description.Kind == StackObjectKind::FixedABI && !Description.Offset) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "fixed ABI stack objects require a fixed offset");
+  }
+  if (Description.Kind == StackObjectKind::Target && !Description.Stack.isTargetStack() &&
+      Description.TargetFlags == 0) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "target stack objects require a target stack ID or nonzero target flags");
+  }
+
+  std::unordered_set<MachineInstrStableID> LifetimeBoundaries;
+  for (const StackObjectLifetimeRange &Range : Description.Lifetime) {
+    if (!Range.Begin.isValid() || !Range.End.isValid() || Range.Begin == Range.End) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "stack object lifetime boundaries must be valid and distinct");
+    }
+    if (!LifetimeBoundaries.insert(Range.Begin).second ||
+        !LifetimeBoundaries.insert(Range.End).second) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "stack object lifetime boundaries must not be reused");
+    }
+  }
+  return {};
+}
+
+Expected<FrameIndex> MachineFrameInfo::createObject(StackObjectDesc Description) {
+  if (Frozen)
+    return makeUnexpected(ErrorCode::InvalidArgument, "frozen frame cannot create stack objects");
+  auto DescriptionResult = verifyDescription(Description);
+  if (!DescriptionResult)
+    return std::unexpected(DescriptionResult.error());
+  if (Objects.size() > std::numeric_limits<std::uint32_t>::max()) {
+    return makeUnexpected(ErrorCode::Unsupported, "stack object index space is exhausted");
+  }
+
+  const FrameIndex Index = FrameIndex::fromValue(static_cast<std::uint32_t>(Objects.size()));
+  Objects.push_back(StackObject(Index, std::move(Description)));
+  return Index;
+}
+
+Expected<StackObject *> MachineFrameInfo::mutableObject(FrameIndex Index) {
+  if (Frozen)
+    return makeUnexpected(ErrorCode::InvalidArgument, "frozen frame cannot modify stack objects");
+  if (Index.value() >= Objects.size())
+    return makeUnexpected(ErrorCode::InvalidArgument, "stack object index is out of range");
+  StackObject &Object = Objects[Index.value()];
+  if (Object.isTombstone())
+    return makeUnexpected(ErrorCode::InvalidArgument, "stack object index is a tombstone");
+  return &Object;
+}
+
+Expected<void> MachineFrameInfo::updateObject(FrameIndex Index, StackObjectDesc Description) {
+  auto DescriptionResult = verifyDescription(Description);
+  if (!DescriptionResult)
+    return std::unexpected(DescriptionResult.error());
+  auto Object = mutableObject(Index);
+  if (!Object)
+    return std::unexpected(Object.error());
+  (*Object)->Description.emplace<StackObjectDesc>(std::move(Description));
+  return {};
+}
+
+Expected<void> MachineFrameInfo::setObjectOffset(FrameIndex Index, std::int64_t Offset) {
+  auto Object = mutableObject(Index);
+  if (!Object)
+    return std::unexpected(Object.error());
+  StackObjectDesc *CurrentDescription = std::get_if<StackObjectDesc>(&(*Object)->Description);
+  if (CurrentDescription == nullptr) {
+    return makeUnexpected(ErrorCode::InternalError,
+                          "live stack object unexpectedly lacks a description");
+  }
+  StackObjectDesc Description = *CurrentDescription;
+  if ((*Object)->isVariableSized()) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "variable-sized stack object cannot have a fixed offset");
+  }
+  Description.Offset = Offset;
+  (*Object)->Description.emplace<StackObjectDesc>(std::move(Description));
+  return {};
+}
+
+Expected<void> MachineFrameInfo::markObjectDead(FrameIndex Index) {
+  auto Object = mutableObject(Index);
+  if (!Object)
+    return std::unexpected(Object.error());
+  StackObjectDesc *Description = std::get_if<StackObjectDesc>(&(*Object)->Description);
+  if (Description == nullptr) {
+    return makeUnexpected(ErrorCode::InternalError,
+                          "live stack object unexpectedly lacks a description");
+  }
+  Description->IsDead = true;
+  return {};
+}
+
+Expected<void> MachineFrameInfo::eraseObject(FrameIndex Index) {
+  auto Object = mutableObject(Index);
+  if (!Object)
+    return std::unexpected(Object.error());
+  (*Object)->Description.emplace<std::monostate>();
+  return {};
+}
+
+const StackObject *MachineFrameInfo::object(FrameIndex Index) const noexcept {
+  if (Index.value() >= Objects.size() || Objects[Index.value()].isTombstone())
+    return nullptr;
+  return &Objects[Index.value()];
+}
+
+std::size_t MachineFrameInfo::liveObjectCount() const noexcept {
+  std::size_t Count = 0;
+  for (const StackObject &Object : Objects) {
+    if (!Object.isTombstone())
+      ++Count;
+  }
+  return Count;
+}
+
+Expected<void> MachineFrameInfo::setMaxCallFrameSize(std::uint64_t Size) {
+  if (Frozen)
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "frozen frame cannot change its maximum call-frame size");
+  MaxCallFrameSize = Size;
+  return {};
+}
+
+Expected<void> MachineFrameInfo::freeze(std::uint64_t Size, Alignment Align) {
+  if (Frozen)
+    return makeUnexpected(ErrorCode::InvalidArgument, "frame layout is already frozen");
+  for (const StackObject &Object : Objects) {
+    if (Object.isTombstone() || Object.isVariableSized())
+      continue;
+    if (!Object.description()->Offset) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "fixed-size stack object is missing its final offset");
+    }
+  }
+  if (Size % Align.bytes() != 0) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "static stack size must be aligned to the stack alignment");
+  }
+
+  StaticStackSize = Size;
+  StackAlign = Align;
+  Frozen = true;
+  return {};
+}
+
+Expected<void> MachineFrameInfo::verify() const {
+  for (std::size_t Position = 0; Position < Objects.size(); ++Position) {
+    const StackObject &Object = Objects[Position];
+    if (Object.index() != FrameIndex::fromValue(static_cast<std::uint32_t>(Position))) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "stack object index does not match its stable table position");
+    }
+    if (Object.isTombstone())
+      continue;
+    auto DescriptionResult = verifyDescription(*Object.description());
+    if (!DescriptionResult)
+      return std::unexpected(DescriptionResult.error());
+    if (Frozen && !Object.isVariableSized() && !Object.description()->Offset) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "frozen fixed-size stack object has no final offset");
+    }
+  }
+
+  if (Frozen != StaticStackSize.has_value()) {
+    return makeUnexpected(ErrorCode::VerificationError,
+                          "frame frozen state and static stack size are inconsistent");
+  }
+  if (Frozen && *StaticStackSize % StackAlign.bytes() != 0) {
+    return makeUnexpected(ErrorCode::VerificationError,
+                          "frozen static stack size violates stack alignment");
+  }
+  return {};
+}
+
+} // namespace rcc