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71 lines
2.6 KiB
C++
71 lines
2.6 KiB
C++
//===-- CmpInstAnalysis.h - Utils to help fold compare insts ----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file holds routines to help analyse compare instructions
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// and fold them into constants or other compare instructions
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_CMPINSTANALYSIS_H
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#define LLVM_ANALYSIS_CMPINSTANALYSIS_H
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#include "llvm/IR/InstrTypes.h"
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namespace llvm {
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class ICmpInst;
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class Value;
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/// Encode a icmp predicate into a three bit mask. These bits are carefully
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/// arranged to allow folding of expressions such as:
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///
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/// (A < B) | (A > B) --> (A != B)
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///
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/// Note that this is only valid if the first and second predicates have the
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/// same sign. It is illegal to do: (A u< B) | (A s> B)
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///
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/// Three bits are used to represent the condition, as follows:
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/// 0 A > B
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/// 1 A == B
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/// 2 A < B
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///
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/// <=> Value Definition
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/// 000 0 Always false
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/// 001 1 A > B
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/// 010 2 A == B
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/// 011 3 A >= B
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/// 100 4 A < B
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/// 101 5 A != B
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/// 110 6 A <= B
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/// 111 7 Always true
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///
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unsigned getICmpCode(const ICmpInst *ICI, bool InvertPred = false);
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/// This is the complement of getICmpCode. It turns a predicate code into
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/// either a constant true or false or the predicate for a new ICmp.
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/// The sign is passed in to determine which kind of predicate to use in the
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/// new ICmp instruction.
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/// Non-NULL return value will be a true or false constant.
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/// NULL return means a new ICmp is needed. The predicate is output in Pred.
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Constant *getPredForICmpCode(unsigned Code, bool Sign, Type *OpTy,
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CmpInst::Predicate &Pred);
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/// Return true if both predicates match sign or if at least one of them is an
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/// equality comparison (which is signless).
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bool predicatesFoldable(CmpInst::Predicate P1, CmpInst::Predicate P2);
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/// Decompose an icmp into the form ((X & Mask) pred 0) if possible. The
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/// returned predicate is either == or !=. Returns false if decomposition
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/// fails.
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bool decomposeBitTestICmp(Value *LHS, Value *RHS, CmpInst::Predicate &Pred,
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Value *&X, APInt &Mask,
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bool LookThroughTrunc = true);
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} // end namespace llvm
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#endif
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