| //===-- 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 |