mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-23 11:13:28 +01:00
c5d014c133
This patch introduces a new KnownBits struct that wraps the two APInt used by computeKnownBits. This allows us to treat them as more of a unit. Initially I've just altered the signatures of computeKnownBits and InstCombine's simplifyDemandedBits to pass a KnownBits reference instead of two separate APInt references. I'll do similar to the SelectionDAG version of computeKnownBits/simplifyDemandedBits as a separate patch. I've added a constructor that allows initializing both APInts to the same bit width with a starting value of 0. This reduces the repeated pattern of initializing both APInts. Once place default constructed the APInts so I added a default constructor for those cases. Going forward I would like to add more methods that will work on the pairs. For example trunc, zext, and sext occur on both APInts together in several places. We should probably add a clear method that can be used to clear both pieces. Maybe a method to check for conflicting information. A method to return (Zero|One) so we don't write it out everywhere. Maybe a method for (Zero|One).isAllOnesValue() to determine if all bits are known. I'm sure there are many other methods we can come up with. Differential Revision: https://reviews.llvm.org/D32376 llvm-svn: 301432
118 lines
3.3 KiB
C++
118 lines
3.3 KiB
C++
//===-- llvm/Analysis/DemandedBits.h - Determine demanded bits --*- C++ -*-===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass implements a demanded bits analysis. A demanded bit is one that
|
|
// contributes to a result; bits that are not demanded can be either zero or
|
|
// one without affecting control or data flow. For example in this sequence:
|
|
//
|
|
// %1 = add i32 %x, %y
|
|
// %2 = trunc i32 %1 to i16
|
|
//
|
|
// Only the lowest 16 bits of %1 are demanded; the rest are removed by the
|
|
// trunc.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_ANALYSIS_DEMANDED_BITS_H
|
|
#define LLVM_ANALYSIS_DEMANDED_BITS_H
|
|
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/ADT/APInt.h"
|
|
#include "llvm/ADT/DenseMap.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
#include "llvm/IR/PassManager.h"
|
|
|
|
namespace llvm {
|
|
|
|
class FunctionPass;
|
|
class Function;
|
|
class Instruction;
|
|
class DominatorTree;
|
|
class AssumptionCache;
|
|
struct KnownBits;
|
|
|
|
class DemandedBits {
|
|
public:
|
|
DemandedBits(Function &F, AssumptionCache &AC, DominatorTree &DT) :
|
|
F(F), AC(AC), DT(DT), Analyzed(false) {}
|
|
|
|
/// Return the bits demanded from instruction I.
|
|
APInt getDemandedBits(Instruction *I);
|
|
|
|
/// Return true if, during analysis, I could not be reached.
|
|
bool isInstructionDead(Instruction *I);
|
|
|
|
void print(raw_ostream &OS);
|
|
|
|
private:
|
|
Function &F;
|
|
AssumptionCache ∾
|
|
DominatorTree &DT;
|
|
|
|
void performAnalysis();
|
|
void determineLiveOperandBits(const Instruction *UserI,
|
|
const Instruction *I, unsigned OperandNo,
|
|
const APInt &AOut, APInt &AB,
|
|
KnownBits &Known, KnownBits &Known2);
|
|
|
|
bool Analyzed;
|
|
|
|
// The set of visited instructions (non-integer-typed only).
|
|
SmallPtrSet<Instruction*, 32> Visited;
|
|
DenseMap<Instruction *, APInt> AliveBits;
|
|
};
|
|
|
|
class DemandedBitsWrapperPass : public FunctionPass {
|
|
private:
|
|
mutable Optional<DemandedBits> DB;
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
DemandedBitsWrapperPass();
|
|
|
|
bool runOnFunction(Function &F) override;
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override;
|
|
|
|
/// Clean up memory in between runs
|
|
void releaseMemory() override;
|
|
|
|
DemandedBits &getDemandedBits() { return *DB; }
|
|
|
|
void print(raw_ostream &OS, const Module *M) const override;
|
|
};
|
|
|
|
/// An analysis that produces \c DemandedBits for a function.
|
|
class DemandedBitsAnalysis : public AnalysisInfoMixin<DemandedBitsAnalysis> {
|
|
friend AnalysisInfoMixin<DemandedBitsAnalysis>;
|
|
static AnalysisKey Key;
|
|
|
|
public:
|
|
/// \brief Provide the result typedef for this analysis pass.
|
|
typedef DemandedBits Result;
|
|
|
|
/// \brief Run the analysis pass over a function and produce demanded bits
|
|
/// information.
|
|
DemandedBits run(Function &F, FunctionAnalysisManager &AM);
|
|
};
|
|
|
|
/// \brief Printer pass for DemandedBits
|
|
class DemandedBitsPrinterPass : public PassInfoMixin<DemandedBitsPrinterPass> {
|
|
raw_ostream &OS;
|
|
|
|
public:
|
|
explicit DemandedBitsPrinterPass(raw_ostream &OS) : OS(OS) {}
|
|
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
|
|
};
|
|
|
|
/// Create a demanded bits analysis pass.
|
|
FunctionPass *createDemandedBitsWrapperPass();
|
|
|
|
} // End llvm namespace
|
|
|
|
#endif
|