| //===-- CmpInstAnalysis.h - Utils to help fold compare insts ----*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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 Type; |
| 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(CmpInst::Predicate Pred); |
| |
| /// This is the complement of getICmpCode. It turns a predicate code into |
| /// either a constant true or false or the predicate for a new ICmp. |
| /// 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 is output in Pred. |
| Constant *getPredForICmpCode(unsigned Code, bool Sign, Type *OpTy, |
| CmpInst::Predicate &Pred); |
| |
| /// 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); |
| |
| /// Similar to getICmpCode but for FCmpInst. This encodes a fcmp predicate |
| /// into a four bit mask. |
| inline unsigned getFCmpCode(CmpInst::Predicate CC) { |
| assert(CmpInst::FCMP_FALSE <= CC && CC <= CmpInst::FCMP_TRUE && |
| "Unexpected FCmp predicate!"); |
| // Take advantage of the bit pattern of CmpInst::Predicate here. |
| // U L G E |
| static_assert(CmpInst::FCMP_FALSE == 0); // 0 0 0 0 |
| static_assert(CmpInst::FCMP_OEQ == 1); // 0 0 0 1 |
| static_assert(CmpInst::FCMP_OGT == 2); // 0 0 1 0 |
| static_assert(CmpInst::FCMP_OGE == 3); // 0 0 1 1 |
| static_assert(CmpInst::FCMP_OLT == 4); // 0 1 0 0 |
| static_assert(CmpInst::FCMP_OLE == 5); // 0 1 0 1 |
| static_assert(CmpInst::FCMP_ONE == 6); // 0 1 1 0 |
| static_assert(CmpInst::FCMP_ORD == 7); // 0 1 1 1 |
| static_assert(CmpInst::FCMP_UNO == 8); // 1 0 0 0 |
| static_assert(CmpInst::FCMP_UEQ == 9); // 1 0 0 1 |
| static_assert(CmpInst::FCMP_UGT == 10); // 1 0 1 0 |
| static_assert(CmpInst::FCMP_UGE == 11); // 1 0 1 1 |
| static_assert(CmpInst::FCMP_ULT == 12); // 1 1 0 0 |
| static_assert(CmpInst::FCMP_ULE == 13); // 1 1 0 1 |
| static_assert(CmpInst::FCMP_UNE == 14); // 1 1 1 0 |
| static_assert(CmpInst::FCMP_TRUE == 15); // 1 1 1 1 |
| return CC; |
| } |
| |
| /// This is the complement of getFCmpCode. It turns a predicate code into |
| /// either a constant true or false or the predicate for a new FCmp. |
| /// Non-NULL return value will be a true or false constant. |
| /// NULL return means a new ICmp is needed. The predicate is output in Pred. |
| Constant *getPredForFCmpCode(unsigned Code, Type *OpTy, |
| CmpInst::Predicate &Pred); |
| |
| /// 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 |