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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 | //===- llvm/Analysis/AssumptionCache.h - Track @llvm.assume ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a pass that keeps track of @llvm.assume intrinsics in
// the functions of a module (allowing assumptions within any function to be
// found cheaply by other parts of the optimizer).
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_ASSUMPTIONCACHE_H
#define LLVM_ANALYSIS_ASSUMPTIONCACHE_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include <memory>
namespace llvm {
/// \brief A cache of @llvm.assume calls within a function.
///
/// This cache provides fast lookup of assumptions within a function by caching
/// them and amortizing the cost of scanning for them across all queries. The
/// cache is also conservatively self-updating so that it will never return
/// incorrect results about a function even as the function is being mutated.
/// However, flushing the cache and rebuilding it (or explicitly updating it)
/// may allow it to discover new assumptions.
class AssumptionCache {
/// \brief The function for which this cache is handling assumptions.
///
/// We track this to lazily populate our assumptions.
Function &F;
/// \brief Vector of weak value handles to calls of the @llvm.assume
/// intrinsic.
SmallVector<WeakVH, 4> AssumeHandles;
/// \brief Flag tracking whether we have scanned the function yet.
///
/// We want to be as lazy about this as possible, and so we scan the function
/// at the last moment.
bool Scanned;
/// \brief Scan the function for assumptions and add them to the cache.
void scanFunction();
public:
/// \brief Construct an AssumptionCache from a function by scanning all of
/// its instructions.
AssumptionCache(Function &F) : F(F), Scanned(false) {}
/// \brief Add an @llvm.assume intrinsic to this function's cache.
///
/// The call passed in must be an instruction within this fuction and must
/// not already be in the cache.
void registerAssumption(CallInst *CI);
/// \brief Clear the cache of @llvm.assume intrinsics for a function.
///
/// It will be re-scanned the next time it is requested.
void clear() {
AssumeHandles.clear();
Scanned = false;
}
/// \brief Access the list of assumption handles currently tracked for this
/// fuction.
///
/// Note that these produce weak handles that may be null. The caller must
/// handle that case.
/// FIXME: We should replace this with pointee_iterator<filter_iterator<...>>
/// when we can write that to filter out the null values. Then caller code
/// will become simpler.
MutableArrayRef<WeakVH> assumptions() {
if (!Scanned)
scanFunction();
return AssumeHandles;
}
};
/// \brief An immutable pass that tracks lazily created \c AssumptionCache
/// objects.
///
/// This is essentially a workaround for the legacy pass manager's weaknesses
/// which associates each assumption cache with Function and clears it if the
/// function is deleted. The nature of the AssumptionCache is that it is not
/// invalidated by any changes to the function body and so this is sufficient
/// to be conservatively correct.
class AssumptionCacheTracker : public ImmutablePass {
/// A callback value handle applied to function objects, which we use to
/// delete our cache of intrinsics for a function when it is deleted.
class FunctionCallbackVH : public CallbackVH {
AssumptionCacheTracker *ACT;
void deleted() override;
public:
typedef DenseMapInfo<Value *> DMI;
FunctionCallbackVH(Value *V, AssumptionCacheTracker *ACT = nullptr)
: CallbackVH(V), ACT(ACT) {}
};
friend FunctionCallbackVH;
typedef DenseMap<FunctionCallbackVH, std::unique_ptr<AssumptionCache>,
FunctionCallbackVH::DMI> FunctionCallsMap;
FunctionCallsMap AssumptionCaches;
public:
/// \brief Get the cached assumptions for a function.
///
/// If no assumptions are cached, this will scan the function. Otherwise, the
/// existing cache will be returned.
AssumptionCache &getAssumptionCache(Function &F);
AssumptionCacheTracker();
~AssumptionCacheTracker();
void releaseMemory() override { AssumptionCaches.shrink_and_clear(); }
void verifyAnalysis() const override;
bool doFinalization(Module &) override {
verifyAnalysis();
return false;
}
static char ID; // Pass identification, replacement for typeid
};
} // end namespace llvm
#endif
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