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
98 lines
3.0 KiB
C++
98 lines
3.0 KiB
C++
//===--- BPF.cpp - Implement BPF target feature support -------------------===//
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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 BPF TargetInfo objects.
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//
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//===----------------------------------------------------------------------===//
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#include "BPF.h"
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#include "Targets.h"
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#include "clang/Basic/MacroBuilder.h"
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#include "clang/Basic/TargetBuiltins.h"
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#include "llvm/ADT/StringRef.h"
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using namespace clang;
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using namespace clang::targets;
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static constexpr Builtin::Info BuiltinInfo[] = {
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#define BUILTIN(ID, TYPE, ATTRS) \
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{#ID, TYPE, ATTRS, nullptr, HeaderDesc::NO_HEADER, ALL_LANGUAGES},
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#include "clang/Basic/BuiltinsBPF.inc"
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};
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void BPFTargetInfo::getTargetDefines(const LangOptions &Opts,
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MacroBuilder &Builder) const {
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Builder.defineMacro("__bpf__");
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Builder.defineMacro("__BPF__");
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std::string CPU = getTargetOpts().CPU;
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if (CPU == "probe") {
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Builder.defineMacro("__BPF_CPU_VERSION__", "0");
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return;
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}
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Builder.defineMacro("__BPF_FEATURE_ADDR_SPACE_CAST");
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if (CPU.empty())
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CPU = "v3";
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if (CPU == "generic" || CPU == "v1") {
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Builder.defineMacro("__BPF_CPU_VERSION__", "1");
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return;
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}
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std::string CpuVerNumStr = CPU.substr(1);
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Builder.defineMacro("__BPF_CPU_VERSION__", CpuVerNumStr);
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Builder.defineMacro("__BPF_FEATURE_MAY_GOTO");
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int CpuVerNum = std::stoi(CpuVerNumStr);
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if (CpuVerNum >= 2)
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Builder.defineMacro("__BPF_FEATURE_JMP_EXT");
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if (CpuVerNum >= 3) {
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Builder.defineMacro("__BPF_FEATURE_JMP32");
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Builder.defineMacro("__BPF_FEATURE_ALU32");
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}
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if (CpuVerNum >= 4) {
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Builder.defineMacro("__BPF_FEATURE_LDSX");
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Builder.defineMacro("__BPF_FEATURE_MOVSX");
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Builder.defineMacro("__BPF_FEATURE_BSWAP");
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Builder.defineMacro("__BPF_FEATURE_SDIV_SMOD");
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Builder.defineMacro("__BPF_FEATURE_GOTOL");
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Builder.defineMacro("__BPF_FEATURE_ST");
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}
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}
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static constexpr llvm::StringLiteral ValidCPUNames[] = {"generic", "v1", "v2",
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"v3", "v4", "probe"};
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bool BPFTargetInfo::isValidCPUName(StringRef Name) const {
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return llvm::is_contained(ValidCPUNames, Name);
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}
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void BPFTargetInfo::fillValidCPUList(SmallVectorImpl<StringRef> &Values) const {
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Values.append(std::begin(ValidCPUNames), std::end(ValidCPUNames));
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}
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ArrayRef<Builtin::Info> BPFTargetInfo::getTargetBuiltins() const {
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return llvm::ArrayRef(BuiltinInfo,
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clang::BPF::LastTSBuiltin - Builtin::FirstTSBuiltin);
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}
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bool BPFTargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
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DiagnosticsEngine &Diags) {
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for (const auto &Feature : Features) {
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if (Feature == "+alu32") {
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HasAlu32 = true;
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}
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}
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return true;
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}
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