7852ebc088
Before llvm20, (void)__sync_fetch_and_add(...) always generates locked xadd insns. In linux kernel upstream discussion [1], it is found that for arm64 architecture, the original semantics of (void)__sync_fetch_and_add(...), i.e., __atomic_fetch_add(...), is preferred in order for jit to emit proper native barrier insns. In llvm commits [2] and [3], (void)__sync_fetch_and_add(...) will generate the following insns: - for cpu v1/v2: locked xadd insns to keep backward compatibility - for cpu v3/v4: __atomic_fetch_add() insns To ensure proper barrier semantics for (void)__sync_fetch_and_add(...), cpu v3/v4 is recommended. This patch enables cpu=v3 as the default cpu version. For users wanting to use cpu v1, -mcpu=v1 needs to be explicitly added to clang/llc command line. [1] https://lore.kernel.org/bpf/ZqqiQQWRnz7H93Hc@google.com/T/#mb68d67bc8f39e35a0c3db52468b9de59b79f021f [2] https://github.com/llvm/llvm-project/pull/101428 [3] https://github.com/llvm/llvm-project/pull/106494
129 lines
3.9 KiB
C++
129 lines
3.9 KiB
C++
//===-- BPFSubtarget.cpp - BPF Subtarget Information ----------------------===//
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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 implements the BPF specific subclass of TargetSubtargetInfo.
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//
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//===----------------------------------------------------------------------===//
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#include "BPFSubtarget.h"
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#include "BPF.h"
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#include "BPFTargetMachine.h"
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#include "GISel/BPFCallLowering.h"
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#include "GISel/BPFLegalizerInfo.h"
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#include "GISel/BPFRegisterBankInfo.h"
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#include "llvm/MC/TargetRegistry.h"
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#include "llvm/TargetParser/Host.h"
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using namespace llvm;
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#define DEBUG_TYPE "bpf-subtarget"
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#define GET_SUBTARGETINFO_TARGET_DESC
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#define GET_SUBTARGETINFO_CTOR
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#include "BPFGenSubtargetInfo.inc"
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static cl::opt<bool> Disable_ldsx("disable-ldsx", cl::Hidden, cl::init(false),
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cl::desc("Disable ldsx insns"));
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static cl::opt<bool> Disable_movsx("disable-movsx", cl::Hidden, cl::init(false),
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cl::desc("Disable movsx insns"));
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static cl::opt<bool> Disable_bswap("disable-bswap", cl::Hidden, cl::init(false),
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cl::desc("Disable bswap insns"));
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static cl::opt<bool> Disable_sdiv_smod("disable-sdiv-smod", cl::Hidden,
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cl::init(false), cl::desc("Disable sdiv/smod insns"));
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static cl::opt<bool> Disable_gotol("disable-gotol", cl::Hidden, cl::init(false),
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cl::desc("Disable gotol insn"));
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static cl::opt<bool>
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Disable_StoreImm("disable-storeimm", cl::Hidden, cl::init(false),
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cl::desc("Disable BPF_ST (immediate store) insn"));
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void BPFSubtarget::anchor() {}
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BPFSubtarget &BPFSubtarget::initializeSubtargetDependencies(StringRef CPU,
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StringRef FS) {
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initializeEnvironment();
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initSubtargetFeatures(CPU, FS);
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ParseSubtargetFeatures(CPU, /*TuneCPU*/ CPU, FS);
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return *this;
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}
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void BPFSubtarget::initializeEnvironment() {
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HasJmpExt = false;
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HasJmp32 = false;
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HasAlu32 = false;
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UseDwarfRIS = false;
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HasLdsx = false;
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HasMovsx = false;
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HasBswap = false;
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HasSdivSmod = false;
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HasGotol = false;
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HasStoreImm = false;
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}
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void BPFSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
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if (CPU.empty())
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CPU = "v3";
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if (CPU == "probe")
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CPU = sys::detail::getHostCPUNameForBPF();
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if (CPU == "generic" || CPU == "v1")
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return;
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if (CPU == "v2") {
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HasJmpExt = true;
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return;
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}
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if (CPU == "v3") {
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HasJmpExt = true;
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HasJmp32 = true;
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HasAlu32 = true;
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return;
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}
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if (CPU == "v4") {
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HasJmpExt = true;
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HasJmp32 = true;
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HasAlu32 = true;
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HasLdsx = !Disable_ldsx;
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HasMovsx = !Disable_movsx;
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HasBswap = !Disable_bswap;
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HasSdivSmod = !Disable_sdiv_smod;
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HasGotol = !Disable_gotol;
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HasStoreImm = !Disable_StoreImm;
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return;
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}
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}
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BPFSubtarget::BPFSubtarget(const Triple &TT, const std::string &CPU,
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const std::string &FS, const TargetMachine &TM)
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: BPFGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS),
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FrameLowering(initializeSubtargetDependencies(CPU, FS)),
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TLInfo(TM, *this) {
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IsLittleEndian = TT.isLittleEndian();
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CallLoweringInfo.reset(new BPFCallLowering(*getTargetLowering()));
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Legalizer.reset(new BPFLegalizerInfo(*this));
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auto *RBI = new BPFRegisterBankInfo(*getRegisterInfo());
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RegBankInfo.reset(RBI);
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InstSelector.reset(createBPFInstructionSelector(
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*static_cast<const BPFTargetMachine *>(&TM), *this, *RBI));
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}
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const CallLowering *BPFSubtarget::getCallLowering() const {
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return CallLoweringInfo.get();
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}
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InstructionSelector *BPFSubtarget::getInstructionSelector() const {
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return InstSelector.get();
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}
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const LegalizerInfo *BPFSubtarget::getLegalizerInfo() const {
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return Legalizer.get();
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}
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const RegisterBankInfo *BPFSubtarget::getRegBankInfo() const {
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return RegBankInfo.get();
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}
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