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//===-- CollectorMetadata.h - Garbage collector metadata ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Gordon Henriksen and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the CollectorMetadata and CollectorModuleMetadata classes,
// which are used as a communication channel from the target code generator
// to the target garbage collector. This interface allows code generators and
// garbage collectors to be developed independently.
//
// The CollectorMetadata class records the data necessary to build a type
// accurate stack map. Roots are specified in the LLVM IR using the llvm.gcroot
// intrinsic, which the code generator understands. The code generator records
// the stack offset for each GC root. Safe points are generated by the code
// generator according to the collector's declared needs (generally at function
// calls).
//
// Safe points and roots are sufficient to build type-accurate stack maps. As a
// refinement, liveness analysis calculates the set of live roots at each safe
// point. Liveness analysis is not presently performed, so all roots are assumed
// live.
//
// CollectorModuleMetadata simply collects CollectorMetadata structures for each
// Function as it is compiled. This is necessary for collectors which must emit
// a stack map for the entire compilation unit. CollectorMetadata outlives the
// MachineFunction from which it is derived, so must not refer to any code
// generator data structures.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_COLLECTORMETADATA_H
#define LLVM_CODEGEN_COLLECTORMETADATA_H
#include "llvm/Pass.h"
#include "llvm/ADT/DenseMap.h"
namespace llvm {
class Constant;
/// Creates a pass to print collector metadata.
///
Pass *createCollectorMetadataPrinter(std::ostream &OS);
/// Creates a pass to destroy collector metadata.
///
Pass *createCollectorMetadataDeleter();
namespace GC {
/// PointKind - The type of a collector-safe point.
///
enum PointKind {
Loop, //< Instr is a loop (backwards branch).
Return, //< Instr is a return instruction.
PreCall, //< Instr is a call instruction.
PostCall //< Instr is the return address of a call.
};
}
/// GCPoint - Metadata for a collector-safe point in machine code.
///
struct GCPoint {
GC::PointKind Kind; //< The kind of the safe point.
unsigned Num; //< Usually a label.
GCPoint(GC::PointKind K, unsigned N) : Kind(K), Num(N) {}
};
/// GCRoot - Metadata for a pointer to an object managed by the garbage
/// collector.
struct GCRoot {
int Num; //< Usually a frame index.
int StackOffset; //< Offset from the stack pointer.
Constant *Metadata; //< From the call to llvm.gcroot.
GCRoot(int N, Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
};
/// CollectorMetadata - Garbage collection metadata for a function.
///
class CollectorMetadata {
public:
typedef std::vector<GCPoint>::iterator iterator;
typedef std::vector<GCRoot>::iterator roots_iterator;
typedef std::vector<GCRoot>::const_iterator live_iterator;
private:
const Function &F;
uint64_t FrameSize;
std::vector<GCRoot> Roots;
std::vector<GCPoint> SafePoints;
// FIXME: Liveness. A 2D BitVector, perhaps?
//
// BitVector Liveness;
//
// bool islive(int point, int root) =
// Liveness[point * SafePoints.size() + root]
//
// The bit vector is the more compact representation where >3.2% of roots
// are live per safe point (1.5% on 64-bit hosts).
friend class CollectorModuleMetadata;
CollectorMetadata(const Function &F);
public:
~CollectorMetadata();
const Function &getFunction() const { return F; }
/// addStackRoot - Registers a root that lives on the stack. Num is the
/// stack object ID for the alloca (if the code generator is using
/// MachineFrameInfo).
void addStackRoot(int Num, Constant *Metadata) {
Roots.push_back(GCRoot(Num, Metadata));
}
/// addSafePoint - Notes the existence of a safe point. Num is the ID of the
/// label just prior to the safe point (if the code generator is using
/// MachineModuleInfo).
void addSafePoint(GC::PointKind Kind, unsigned Num) {
SafePoints.push_back(GCPoint(Kind, Num));
}
/// getFrameSize/setFrameSize - Records the function's frame size.
///
uint64_t getFrameSize() const { return FrameSize; }
void setFrameSize(uint64_t S) { FrameSize = S; }
/// begin/end - Iterators for safe points.
///
iterator begin() { return SafePoints.begin(); }
iterator end() { return SafePoints.end(); }
size_t size() const { return SafePoints.size(); }
/// roots_begin/roots_end - Iterators for all roots in the function.
///
roots_iterator roots_begin() { return Roots.begin(); }
roots_iterator roots_end () { return Roots.end(); }
size_t roots_size() const { return Roots.size(); }
/// live_begin/live_end - Iterators for live roots at a given safe point.
///
live_iterator live_begin(const iterator &p) { return roots_begin(); }
live_iterator live_end (const iterator &p) { return roots_end(); }
size_t live_size(const iterator &p) const { return roots_size(); }
};
/// CollectorModuleMetadata - Garbage collection metadata for a whole module.
///
class CollectorModuleMetadata : public ImmutablePass {
typedef std::vector<CollectorMetadata*> list_type;
typedef DenseMap<const Function*,CollectorMetadata*> map_type;
Module *Mod;
list_type Functions;
map_type Map;
public:
typedef list_type::iterator iterator;
static char ID;
CollectorModuleMetadata();
~CollectorModuleMetadata();
/// clear - Used to delete module metadata. Collector invokes this as
/// necessary.
void clear();
/// begin/end - Iterators for function metadata.
///
iterator begin() { return Functions.begin(); }
iterator end() { return Functions.end(); }
/// insert - Creates metadata for a function.
///
CollectorMetadata& insert(const Function *F);
/// get - Looks up existing function metadata.
///
CollectorMetadata* get(const Function *F) const;
};
}
#endif
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