mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-23 17:29:19 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207196 91177308-0d34-0410-b5e6-96231b3b80d8
97 lines
3.8 KiB
C++
97 lines
3.8 KiB
C++
//===- CmpInstAnalysis.cpp - Utils to help fold compares ---------------===//
|
|
//
|
|
// 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Utils/CmpInstAnalysis.h"
|
|
#include "llvm/IR/Constants.h"
|
|
#include "llvm/IR/Instructions.h"
|
|
|
|
using namespace llvm;
|
|
|
|
/// getICmpCode - 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. 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 llvm::getICmpCode(const ICmpInst *ICI, bool InvertPred) {
|
|
ICmpInst::Predicate Pred = InvertPred ? ICI->getInversePredicate()
|
|
: ICI->getPredicate();
|
|
switch (Pred) {
|
|
// False -> 0
|
|
case ICmpInst::ICMP_UGT: return 1; // 001
|
|
case ICmpInst::ICMP_SGT: return 1; // 001
|
|
case ICmpInst::ICMP_EQ: return 2; // 010
|
|
case ICmpInst::ICMP_UGE: return 3; // 011
|
|
case ICmpInst::ICMP_SGE: return 3; // 011
|
|
case ICmpInst::ICMP_ULT: return 4; // 100
|
|
case ICmpInst::ICMP_SLT: return 4; // 100
|
|
case ICmpInst::ICMP_NE: return 5; // 101
|
|
case ICmpInst::ICMP_ULE: return 6; // 110
|
|
case ICmpInst::ICMP_SLE: return 6; // 110
|
|
// True -> 7
|
|
default:
|
|
llvm_unreachable("Invalid ICmp predicate!");
|
|
}
|
|
}
|
|
|
|
/// getICmpValue - 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 *llvm::getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
|
|
CmpInst::Predicate &NewICmpPred) {
|
|
switch (Code) {
|
|
default: llvm_unreachable("Illegal ICmp code!");
|
|
case 0: // False.
|
|
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
|
|
case 1: NewICmpPred = Sign ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; break;
|
|
case 2: NewICmpPred = ICmpInst::ICMP_EQ; break;
|
|
case 3: NewICmpPred = Sign ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; break;
|
|
case 4: NewICmpPred = Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; break;
|
|
case 5: NewICmpPred = ICmpInst::ICMP_NE; break;
|
|
case 6: NewICmpPred = Sign ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; break;
|
|
case 7: // True.
|
|
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 1);
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// PredicatesFoldable - Return true if both predicates match sign or if at
|
|
/// least one of them is an equality comparison (which is signless).
|
|
bool llvm::PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
|
|
return (CmpInst::isSigned(p1) == CmpInst::isSigned(p2)) ||
|
|
(CmpInst::isSigned(p1) && ICmpInst::isEquality(p2)) ||
|
|
(CmpInst::isSigned(p2) && ICmpInst::isEquality(p1));
|
|
}
|