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5746dd289e
This is a part of the refactoring to unify isSafeToLoadUnconditionally and isDereferenceablePointer functions. In subsequent change I'm going to eliminate isDerferenceableAndAlignedPointer from Loads API, leaving isSafeToLoadSpecualtively the only function to check is load instruction can be speculated. Reviewed By: hfinkel Differential Revision: http://reviews.llvm.org/D16180 llvm-svn: 261736
88 lines
4.0 KiB
C++
88 lines
4.0 KiB
C++
//===- Loads.h - Local load analysis --------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares simple local analyses for load instructions.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LOADS_H
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#define LLVM_ANALYSIS_LOADS_H
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/Support/CommandLine.h"
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namespace llvm {
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class DataLayout;
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class MDNode;
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/// isDereferenceablePointer - Return true if this is always a dereferenceable
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/// pointer. If the context instruction is specified perform context-sensitive
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/// analysis and return true if the pointer is dereferenceable at the
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/// specified instruction.
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bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
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const Instruction *CtxI = nullptr,
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const DominatorTree *DT = nullptr,
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const TargetLibraryInfo *TLI = nullptr);
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/// Returns true if V is always a dereferenceable pointer with alignment
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/// greater or equal than requested. If the context instruction is specified
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/// performs context-sensitive analysis and returns true if the pointer is
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/// dereferenceable at the specified instruction.
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bool isDereferenceableAndAlignedPointer(const Value *V, unsigned Align,
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const DataLayout &DL,
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const Instruction *CtxI = nullptr,
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const DominatorTree *DT = nullptr,
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const TargetLibraryInfo *TLI = nullptr);
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/// isSafeToLoadUnconditionally - Return true if we know that executing a load
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/// from this value cannot trap.
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///
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/// If DT is specified this method performs context-sensitive analysis.
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///
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/// If it is not obviously safe to load from the specified pointer, we do a
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/// quick local scan of the basic block containing ScanFrom, to determine if
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/// the address is already accessed.
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bool isSafeToLoadUnconditionally(Value *V, unsigned Align,
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Instruction *ScanFrom,
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const DominatorTree *DT = nullptr,
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const TargetLibraryInfo *TLI = nullptr);
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/// DefMaxInstsToScan - the default number of maximum instructions
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/// to scan in the block, used by FindAvailableLoadedValue().
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extern cl::opt<unsigned> DefMaxInstsToScan;
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/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at
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/// the instruction before ScanFrom) checking to see if we have the value at
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/// the memory address *Ptr locally available within a small number of
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/// instructions. If the value is available, return it.
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///
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/// If not, return the iterator for the last validated instruction that the
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/// value would be live through. If we scanned the entire block and didn't
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/// find something that invalidates *Ptr or provides it, ScanFrom would be
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/// left at begin() and this returns null. ScanFrom could also be left
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///
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/// MaxInstsToScan specifies the maximum instructions to scan in the block.
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/// If it is set to 0, it will scan the whole block. You can also optionally
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/// specify an alias analysis implementation, which makes this more precise.
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///
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/// If AATags is non-null and a load or store is found, the AA tags from the
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/// load or store are recorded there. If there are no AA tags or if no access
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/// is found, it is left unmodified.
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Value *FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
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BasicBlock::iterator &ScanFrom,
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unsigned MaxInstsToScan = DefMaxInstsToScan,
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AliasAnalysis *AA = nullptr,
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AAMDNodes *AATags = nullptr);
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}
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#endif
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