//===-- 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