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