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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197658 91177308-0d34-0410-b5e6-96231b3b80d8
67 lines
2.3 KiB
C++
67 lines
2.3 KiB
C++
//===-- CmpInstAnalysis.h - Utils to help fold compare insts ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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_TRANSFORMS_UTILS_CMPINSTANALYSIS_H
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#define LLVM_TRANSFORMS_UTILS_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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/// getICmpCode - Encode a icmp predicate into a three bit mask. These bits
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/// are carefully 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. 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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/// getICmpValue - This is the complement of getICmpCode, which turns an
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/// opcode and two operands into either a constant true or false, or the
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/// predicate for a new ICmp instruction. The sign is passed in to determine
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/// which kind of predicate to use in the 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 for which is
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/// output in NewICmpPred.
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Value *getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
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CmpInst::Predicate &NewICmpPred);
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/// PredicatesFoldable - Return true if both predicates match sign or if at
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/// least one of them is an equality comparison (which is signless).
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bool PredicatesFoldable(CmpInst::Predicate p1, CmpInst::Predicate p2);
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} // end namespace llvm
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#endif
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