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//===-- CmpInstAnalysis.h - Utils to help fold compare insts ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file holds routines to help analyse compare instructions
// and fold them into constants or other compare instructions
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_CMPINSTANALYSIS_H
#define LLVM_ANALYSIS_CMPINSTANALYSIS_H
#include "llvm/IR/InstrTypes.h"
namespace llvm {
class ICmpInst;
class Value;
/// Encode a icmp predicate into a three bit mask. These bits are carefully
/// arranged to allow folding of expressions such as:
///
/// (A < B) | (A > B) --> (A != B)
///
/// Note that this is only valid if the first and second predicates have the
/// same sign. It is illegal to do: (A u< B) | (A s> B)
///
/// Three bits are used to represent the condition, as follows:
/// 0 A > B
/// 1 A == B
/// 2 A < B
///
/// <=> Value Definition
/// 000 0 Always false
/// 001 1 A > B
/// 010 2 A == B
/// 011 3 A >= B
/// 100 4 A < B
/// 101 5 A != B
/// 110 6 A <= B
/// 111 7 Always true
///
unsigned getICmpCode(const ICmpInst *ICI, bool InvertPred = false);
/// This is the complement of getICmpCode, which turns an opcode and two
/// operands into either a constant true or false, or the predicate for a new
/// ICmp instruction. The sign is passed in to determine which kind of
/// predicate to use in the new icmp instruction.
/// Non-NULL return value will be a true or false constant.
/// NULL return means a new ICmp is needed. The predicate for which is output
/// in NewICmpPred.
Value *getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
CmpInst::Predicate &NewICmpPred);
/// Return true if both predicates match sign or if at least one of them is an
/// equality comparison (which is signless).
bool PredicatesFoldable(CmpInst::Predicate p1, CmpInst::Predicate p2);
/// Decompose an icmp into the form ((X & Mask) pred 0) if possible. The
/// returned predicate is either == or !=. Returns false if decomposition
/// fails.
bool decomposeBitTestICmp(Value *LHS, Value *RHS, CmpInst::Predicate &Pred,
Value *&X, APInt &Mask,
bool LookThroughTrunc = true);
} // end namespace llvm
#endif
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