a260ae7160
This patch implemented TTI.IntImmCost() properly. Each BPF insn has 32bit immediate space, so for any immediate which can be represented as 32bit signed int, the cost is technically free. If an int cannot be presented as a 32bit signed int, a ld_imm64 instruction is needed and a TCC_Basic is returned. This change is motivated when we observed that several bpf selftests failed with latest llvm trunk, e.g., #10/16 strobemeta.o:FAIL #10/17 strobemeta_nounroll1.o:FAIL #10/18 strobemeta_nounroll2.o:FAIL #10/19 strobemeta_subprogs.o:FAIL #96 snprintf_btf:FAIL The reason of the failure is due to that SpeculateAroundPHIsPass did aggressive transformation which alters control flow for which currently verifer cannot handle well. In llvm12, SpeculateAroundPHIsPass is not called. SpeculateAroundPHIsPass relied on TTI.getIntImmCost() and TTI.getIntImmCostInst() for profitability analysis. This patch implemented TTI.getIntImmCost() properly for BPF backend which also prevented transformation which caused the above test failures. Differential Revision: https://reviews.llvm.org/D96448
50 lines
1.7 KiB
C++
50 lines
1.7 KiB
C++
//===-- BPFTargetMachine.h - Define TargetMachine for BPF --- 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 declares the BPF specific subclass of TargetMachine.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_TARGET_BPF_BPFTARGETMACHINE_H
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#define LLVM_LIB_TARGET_BPF_BPFTARGETMACHINE_H
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#include "BPFSubtarget.h"
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#include "llvm/Target/TargetMachine.h"
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namespace llvm {
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class BPFTargetMachine : public LLVMTargetMachine {
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std::unique_ptr<TargetLoweringObjectFile> TLOF;
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BPFSubtarget Subtarget;
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public:
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BPFTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
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StringRef FS, const TargetOptions &Options,
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Optional<Reloc::Model> RM, Optional<CodeModel::Model> CM,
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CodeGenOpt::Level OL, bool JIT);
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const BPFSubtarget *getSubtargetImpl() const { return &Subtarget; }
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const BPFSubtarget *getSubtargetImpl(const Function &) const override {
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return &Subtarget;
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}
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TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
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TargetTransformInfo getTargetTransformInfo(const Function &F) override;
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TargetLoweringObjectFile *getObjFileLowering() const override {
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return TLOF.get();
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}
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void adjustPassManager(PassManagerBuilder &) override;
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void registerPassBuilderCallbacks(PassBuilder &PB,
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bool DebugPassManager) override;
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};
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}
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#endif
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