#ifndef LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
#define LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
+#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/Pass.h"
#include "llvm/Support/BranchProbability.h"
#include <climits>
namespace llvm {
-class raw_ostream;
-class MachineBasicBlock;
-
class MachineBranchProbabilityInfo : public ImmutablePass {
+ virtual void anchor();
// Default weight value. Used when we don't have information about the edge.
// TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
// weight to just "inherit" the non-zero weight of an adjacent successor.
static const uint32_t DEFAULT_WEIGHT = 16;
- // Get sum of the block successors' weights.
- uint32_t getSumForBlock(MachineBasicBlock *MBB) const;
-
public:
static char ID;
// Return edge weight. If we don't have any informations about it - return
// DEFAULT_WEIGHT.
- uint32_t getEdgeWeight(MachineBasicBlock *Src, MachineBasicBlock *Dst) const;
+ uint32_t getEdgeWeight(const MachineBasicBlock *Src,
+ const MachineBasicBlock *Dst) const;
+
+ // Same thing, but using a const_succ_iterator from Src. This is faster when
+ // the iterator is already available.
+ uint32_t getEdgeWeight(const MachineBasicBlock *Src,
+ MachineBasicBlock::const_succ_iterator Dst) const;
+
+ // Get sum of the block successors' weights, potentially scaling them to fit
+ // within 32-bits. If scaling is required, sets Scale based on the necessary
+ // adjustment. Any edge weights used with the sum should be divided by Scale.
+ uint32_t getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const;
// A 'Hot' edge is an edge which probability is >= 80%.
bool isEdgeHot(MachineBasicBlock *Src, MachineBasicBlock *Dst) const;
// Return a hot successor for the block BB or null if there isn't one.
+ // NB: This routine's complexity is linear on the number of successors.
MachineBasicBlock *getHotSucc(MachineBasicBlock *MBB) const;
// Return a probability as a fraction between 0 (0% probability) and
// 1 (100% probability), however the value is never equal to 0, and can be 1
// only iff SRC block has only one successor.
+ // NB: This routine's complexity is linear on the number of successors of
+ // Src. Querying sequentially for each successor's probability is a quadratic
+ // query pattern.
BranchProbability getEdgeProbability(MachineBasicBlock *Src,
MachineBasicBlock *Dst) const;