299 lines
8.9 KiB
C++
299 lines
8.9 KiB
C++
//===-- RISCVMCExpr.cpp - RISCV specific MC expression classes ------------===//
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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 contains the implementation of the assembly expression modifiers
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// accepted by the RISCV architecture (e.g. ":lo12:", ":gottprel_g1:", ...).
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//
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//===----------------------------------------------------------------------===//
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#include "RISCVMCExpr.h"
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#include "MCTargetDesc/RISCVAsmBackend.h"
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#include "RISCV.h"
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#include "RISCVFixupKinds.h"
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbolELF.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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using namespace llvm;
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#define DEBUG_TYPE "riscvmcexpr"
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const RISCVMCExpr *RISCVMCExpr::create(const MCExpr *Expr, VariantKind Kind,
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MCContext &Ctx) {
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return new (Ctx) RISCVMCExpr(Expr, Kind);
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}
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void RISCVMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
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VariantKind Kind = getKind();
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bool HasVariant = ((Kind != VK_RISCV_None) && (Kind != VK_RISCV_CALL) &&
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(Kind != VK_RISCV_CALL_PLT));
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if (HasVariant)
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OS << '%' << getVariantKindName(getKind()) << '(';
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Expr->print(OS, MAI);
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if (Kind == VK_RISCV_CALL_PLT)
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OS << "@plt";
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if (HasVariant)
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OS << ')';
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}
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const MCFixup *RISCVMCExpr::getPCRelHiFixup() const {
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MCValue AUIPCLoc;
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if (!getSubExpr()->evaluateAsRelocatable(AUIPCLoc, nullptr, nullptr))
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return nullptr;
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const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
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if (!AUIPCSRE)
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return nullptr;
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const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
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const auto *DF = dyn_cast_or_null<MCDataFragment>(AUIPCSymbol->getFragment());
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if (!DF)
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return nullptr;
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uint64_t Offset = AUIPCSymbol->getOffset();
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if (DF->getContents().size() == Offset) {
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DF = dyn_cast_or_null<MCDataFragment>(DF->getNextNode());
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if (!DF)
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return nullptr;
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Offset = 0;
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}
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for (const MCFixup &F : DF->getFixups()) {
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if (F.getOffset() != Offset)
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continue;
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switch ((unsigned)F.getKind()) {
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default:
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continue;
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case RISCV::fixup_riscv_got_hi20:
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case RISCV::fixup_riscv_tls_got_hi20:
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case RISCV::fixup_riscv_tls_gd_hi20:
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case RISCV::fixup_riscv_pcrel_hi20:
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return &F;
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}
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}
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return nullptr;
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}
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bool RISCVMCExpr::evaluatePCRelLo(MCValue &Res, const MCAsmLayout *Layout,
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const MCFixup *Fixup) const {
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// VK_RISCV_PCREL_LO has to be handled specially. The MCExpr inside is
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// actually the location of a auipc instruction with a VK_RISCV_PCREL_HI fixup
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// pointing to the real target. We need to generate an MCValue in the form of
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// (<real target> + <offset from this fixup to the auipc fixup>). The Fixup
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// is pcrel relative to the VK_RISCV_PCREL_LO fixup, so we need to add the
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// offset to the VK_RISCV_PCREL_HI Fixup from VK_RISCV_PCREL_LO to correct.
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// Don't try to evaluate if the fixup will be forced as a relocation (e.g.
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// as linker relaxation is enabled). If we evaluated pcrel_lo in this case,
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// the modified fixup will be converted into a relocation that no longer
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// points to the pcrel_hi as the linker requires.
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auto &RAB =
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static_cast<RISCVAsmBackend &>(Layout->getAssembler().getBackend());
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if (RAB.willForceRelocations())
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return false;
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MCValue AUIPCLoc;
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if (!getSubExpr()->evaluateAsValue(AUIPCLoc, *Layout))
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return false;
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const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
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// Don't try to evaluate %pcrel_hi/%pcrel_lo pairs that cross fragment
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// boundries.
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if (!AUIPCSRE ||
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findAssociatedFragment() != AUIPCSRE->findAssociatedFragment())
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return false;
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const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
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if (!AUIPCSymbol)
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return false;
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const MCFixup *TargetFixup = getPCRelHiFixup();
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if (!TargetFixup)
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return false;
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if ((unsigned)TargetFixup->getKind() != RISCV::fixup_riscv_pcrel_hi20)
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return false;
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MCValue Target;
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if (!TargetFixup->getValue()->evaluateAsValue(Target, *Layout))
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return false;
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if (!Target.getSymA() || !Target.getSymA()->getSymbol().isInSection())
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return false;
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if (&Target.getSymA()->getSymbol().getSection() !=
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findAssociatedFragment()->getParent())
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return false;
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uint64_t AUIPCOffset = AUIPCSymbol->getOffset();
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Res = MCValue::get(Target.getSymA(), nullptr,
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Target.getConstant() + (Fixup->getOffset() - AUIPCOffset));
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return true;
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}
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bool RISCVMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
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const MCAsmLayout *Layout,
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const MCFixup *Fixup) const {
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if (Kind == VK_RISCV_PCREL_LO && evaluatePCRelLo(Res, Layout, Fixup))
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return true;
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if (!getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup))
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return false;
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// Some custom fixup types are not valid with symbol difference expressions
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if (Res.getSymA() && Res.getSymB()) {
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switch (getKind()) {
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default:
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return true;
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case VK_RISCV_LO:
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case VK_RISCV_HI:
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case VK_RISCV_PCREL_LO:
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case VK_RISCV_PCREL_HI:
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case VK_RISCV_GOT_HI:
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case VK_RISCV_TPREL_LO:
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case VK_RISCV_TPREL_HI:
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case VK_RISCV_TPREL_ADD:
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case VK_RISCV_TLS_GOT_HI:
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case VK_RISCV_TLS_GD_HI:
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return false;
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}
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}
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return true;
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}
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void RISCVMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
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Streamer.visitUsedExpr(*getSubExpr());
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}
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RISCVMCExpr::VariantKind RISCVMCExpr::getVariantKindForName(StringRef name) {
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return StringSwitch<RISCVMCExpr::VariantKind>(name)
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.Case("lo", VK_RISCV_LO)
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.Case("hi", VK_RISCV_HI)
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.Case("pcrel_lo", VK_RISCV_PCREL_LO)
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.Case("pcrel_hi", VK_RISCV_PCREL_HI)
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.Case("got_pcrel_hi", VK_RISCV_GOT_HI)
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.Case("tprel_lo", VK_RISCV_TPREL_LO)
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.Case("tprel_hi", VK_RISCV_TPREL_HI)
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.Case("tprel_add", VK_RISCV_TPREL_ADD)
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.Case("tls_ie_pcrel_hi", VK_RISCV_TLS_GOT_HI)
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.Case("tls_gd_pcrel_hi", VK_RISCV_TLS_GD_HI)
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.Default(VK_RISCV_Invalid);
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}
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StringRef RISCVMCExpr::getVariantKindName(VariantKind Kind) {
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switch (Kind) {
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default:
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llvm_unreachable("Invalid ELF symbol kind");
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case VK_RISCV_LO:
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return "lo";
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case VK_RISCV_HI:
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return "hi";
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case VK_RISCV_PCREL_LO:
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return "pcrel_lo";
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case VK_RISCV_PCREL_HI:
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return "pcrel_hi";
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case VK_RISCV_GOT_HI:
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return "got_pcrel_hi";
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case VK_RISCV_TPREL_LO:
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return "tprel_lo";
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case VK_RISCV_TPREL_HI:
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return "tprel_hi";
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case VK_RISCV_TPREL_ADD:
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return "tprel_add";
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case VK_RISCV_TLS_GOT_HI:
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return "tls_ie_pcrel_hi";
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case VK_RISCV_TLS_GD_HI:
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return "tls_gd_pcrel_hi";
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}
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}
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static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
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switch (Expr->getKind()) {
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case MCExpr::Target:
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llvm_unreachable("Can't handle nested target expression");
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break;
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case MCExpr::Constant:
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break;
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case MCExpr::Binary: {
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const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr);
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fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm);
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fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm);
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break;
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}
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case MCExpr::SymbolRef: {
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// We're known to be under a TLS fixup, so any symbol should be
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// modified. There should be only one.
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const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr);
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cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS);
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break;
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}
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case MCExpr::Unary:
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fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm);
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break;
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}
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}
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void RISCVMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
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switch (getKind()) {
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default:
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return;
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case VK_RISCV_TPREL_HI:
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case VK_RISCV_TLS_GOT_HI:
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case VK_RISCV_TLS_GD_HI:
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break;
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}
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fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm);
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}
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bool RISCVMCExpr::evaluateAsConstant(int64_t &Res) const {
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MCValue Value;
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if (Kind == VK_RISCV_PCREL_HI || Kind == VK_RISCV_PCREL_LO ||
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Kind == VK_RISCV_GOT_HI || Kind == VK_RISCV_TPREL_HI ||
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Kind == VK_RISCV_TPREL_LO || Kind == VK_RISCV_TPREL_ADD ||
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Kind == VK_RISCV_TLS_GOT_HI || Kind == VK_RISCV_TLS_GD_HI ||
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Kind == VK_RISCV_CALL || Kind == VK_RISCV_CALL_PLT)
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return false;
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if (!getSubExpr()->evaluateAsRelocatable(Value, nullptr, nullptr))
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return false;
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if (!Value.isAbsolute())
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return false;
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Res = evaluateAsInt64(Value.getConstant());
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return true;
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}
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int64_t RISCVMCExpr::evaluateAsInt64(int64_t Value) const {
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switch (Kind) {
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default:
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llvm_unreachable("Invalid kind");
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case VK_RISCV_LO:
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return SignExtend64<12>(Value);
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case VK_RISCV_HI:
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// Add 1 if bit 11 is 1, to compensate for low 12 bits being negative.
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return ((Value + 0x800) >> 12) & 0xfffff;
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}
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}
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