mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-25 04:02:41 +01:00
f6a86e448a
Kuniyuki Iwashima reported in [1] that llvm compiler may convert a loop exit condition with "i < bound" to "i != bound", where "i" is the loop index variable and "bound" is the upper bound. In case that "bound" is not a constant, verifier will always have "i != bound" true, which will cause verifier failure since to verifier this is an infinite loop. The fix is to avoid transforming "i < bound" to "i != bound". In llvm, the transformation is done by IndVarSimplify pass. The compiler checks loop condition cost (i = i + 1) and if the cost is lower, it may transform "i < bound" to "i != bound". This patch implemented getArithmeticInstrCost() in BPF TargetTransformInfo class to return a higher cost for such an operation, which will prevent the transformation for the test case added in this patch. [1] https://lore.kernel.org/netdev/1994df05-8f01-371f-3c3b-d33d7836878c@fb.com/ Differential Revision: https://reviews.llvm.org/D107483 (cherry picked from commit e52946b9ababcbf8e6f40b1b15900ae2e795a1c6)
80 lines
3.1 KiB
C++
80 lines
3.1 KiB
C++
//===------ BPFTargetTransformInfo.h - BPF specific TTI ---------*- 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 uses the target's specific information to
|
|
// provide more precise answers to certain TTI queries, while letting the
|
|
// target independent and default TTI implementations handle the rest.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_LIB_TARGET_BPF_BPFTARGETTRANSFORMINFO_H
|
|
#define LLVM_LIB_TARGET_BPF_BPFTARGETTRANSFORMINFO_H
|
|
|
|
#include "BPFTargetMachine.h"
|
|
#include "llvm/Analysis/TargetTransformInfo.h"
|
|
#include "llvm/CodeGen/BasicTTIImpl.h"
|
|
#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
|
|
|
|
namespace llvm {
|
|
class BPFTTIImpl : public BasicTTIImplBase<BPFTTIImpl> {
|
|
typedef BasicTTIImplBase<BPFTTIImpl> BaseT;
|
|
typedef TargetTransformInfo TTI;
|
|
friend BaseT;
|
|
|
|
const BPFSubtarget *ST;
|
|
const BPFTargetLowering *TLI;
|
|
|
|
const BPFSubtarget *getST() const { return ST; }
|
|
const BPFTargetLowering *getTLI() const { return TLI; }
|
|
|
|
public:
|
|
explicit BPFTTIImpl(const BPFTargetMachine *TM, const Function &F)
|
|
: BaseT(TM, F.getParent()->getDataLayout()), ST(TM->getSubtargetImpl(F)),
|
|
TLI(ST->getTargetLowering()) {}
|
|
|
|
int getIntImmCost(const APInt &Imm, Type *Ty, TTI::TargetCostKind CostKind) {
|
|
if (Imm.getBitWidth() <= 64 && isInt<32>(Imm.getSExtValue()))
|
|
return TTI::TCC_Free;
|
|
|
|
return TTI::TCC_Basic;
|
|
}
|
|
|
|
InstructionCost getCmpSelInstrCost(unsigned Opcode, Type *ValTy, Type *CondTy,
|
|
CmpInst::Predicate VecPred,
|
|
TTI::TargetCostKind CostKind,
|
|
const llvm::Instruction *I = nullptr) {
|
|
if (Opcode == Instruction::Select)
|
|
return SCEVCheapExpansionBudget.getValue();
|
|
|
|
return BaseT::getCmpSelInstrCost(Opcode, ValTy, CondTy, VecPred, CostKind,
|
|
I);
|
|
}
|
|
|
|
InstructionCost getArithmeticInstrCost(
|
|
unsigned Opcode, Type *Ty,
|
|
TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput,
|
|
TTI::OperandValueKind Opd1Info = TTI::OK_AnyValue,
|
|
TTI::OperandValueKind Opd2Info = TTI::OK_AnyValue,
|
|
TTI::OperandValueProperties Opd1PropInfo = TTI::OP_None,
|
|
TTI::OperandValueProperties Opd2PropInfo = TTI::OP_None,
|
|
ArrayRef<const Value *> Args = ArrayRef<const Value *>(),
|
|
const Instruction *CxtI = nullptr) {
|
|
int ISD = TLI->InstructionOpcodeToISD(Opcode);
|
|
if (ISD == ISD::ADD && CostKind == TTI::TCK_RecipThroughput)
|
|
return SCEVCheapExpansionBudget.getValue() + 1;
|
|
|
|
return BaseT::getArithmeticInstrCost(Opcode, Ty, CostKind, Opd1Info,
|
|
Opd2Info, Opd1PropInfo,
|
|
Opd2PropInfo);
|
|
}
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
#endif // LLVM_LIB_TARGET_BPF_BPFTARGETTRANSFORMINFO_H
|