bbea64250f
This re-architects the RISCV relocation handling to bring the implementation closer in line with the implementation in binutils. We would previously aggressively resolve the relocation. With this restructuring, we always will emit a paired relocation for any symbolic difference of the type of S±T[±C] where S and T are labels and C is a constant. GAS has a special target hook controlled by `RELOC_EXPANSION_POSSIBLE` which indicates that a fixup may be expanded into multiple relocations. This is used by the RISCV backend to always emit a paired relocation - either ADD[WIDTH] + SUB[WIDTH] for text relocations or SET[WIDTH] + SUB[WIDTH] for a debug info relocation. Irrespective of whether linker relaxation support is enabled, symbolic difference is always emitted as a paired relocation. This change also sinks the target specific behaviour down into the target specific area rather than exposing it to the shared relocation handling. In the process, we also sink the "special" handling for debug information down into the RISCV target. Although this improves the path for the other targets, this is not necessarily entirely ideal either. The changes in the debug info emission could be done through another type of hook as this functionality would be required by any other target which wishes to do linker relaxation. However, as there are no other targets in LLVM which currently do this, this is a reasonable thing to do until such time as the code needs to be shared. Improve the handling of the relocation (and add a reduced test case from the Linux kernel) to ensure that we handle complex expressions for symbolic difference. This ensures that we correct relocate symbols with the adddends normalized and associated with the addition portion of the paired relocation. This change also addresses some review comments from Alex Bradbury about the relocations meant for use in the DWARF CFA being named incorrectly (using ADD6 instead of SET6) in the original change which introduced the relocation type. This resolves the issues with the symbolic difference emission sufficiently to enable building the Linux kernel with clang+IAS+lld (without linker relaxation). Resolves PR50153, PR50156! Fixes: ClangBuiltLinux/linux#1023, ClangBuiltLinux/linux#1143 Reviewed By: nickdesaulniers, maskray Differential Revision: https://reviews.llvm.org/D103539
115 lines
3.7 KiB
C++
115 lines
3.7 KiB
C++
//===-- RISCVELFStreamer.h - RISCV ELF Target Streamer ---------*- 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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#ifndef LLVM_LIB_TARGET_RISCV_RISCVELFSTREAMER_H
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#define LLVM_LIB_TARGET_RISCV_RISCVELFSTREAMER_H
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#include "RISCVTargetStreamer.h"
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#include "llvm/MC/MCELFStreamer.h"
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namespace llvm {
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class RISCVTargetELFStreamer : public RISCVTargetStreamer {
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private:
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enum class AttributeType { Hidden, Numeric, Text, NumericAndText };
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struct AttributeItem {
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AttributeType Type;
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unsigned Tag;
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unsigned IntValue;
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std::string StringValue;
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};
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StringRef CurrentVendor;
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SmallVector<AttributeItem, 64> Contents;
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MCSection *AttributeSection = nullptr;
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AttributeItem *getAttributeItem(unsigned Attribute) {
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for (size_t i = 0; i < Contents.size(); ++i)
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if (Contents[i].Tag == Attribute)
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return &Contents[i];
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return nullptr;
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}
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void setAttributeItem(unsigned Attribute, unsigned Value,
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bool OverwriteExisting) {
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// Look for existing attribute item.
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if (AttributeItem *Item = getAttributeItem(Attribute)) {
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if (!OverwriteExisting)
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return;
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Item->Type = AttributeType::Numeric;
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Item->IntValue = Value;
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return;
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}
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// Create new attribute item.
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Contents.push_back({AttributeType::Numeric, Attribute, Value, ""});
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}
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void setAttributeItem(unsigned Attribute, StringRef Value,
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bool OverwriteExisting) {
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// Look for existing attribute item.
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if (AttributeItem *Item = getAttributeItem(Attribute)) {
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if (!OverwriteExisting)
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return;
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Item->Type = AttributeType::Text;
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Item->StringValue = std::string(Value);
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return;
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}
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// Create new attribute item.
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Contents.push_back({AttributeType::Text, Attribute, 0, std::string(Value)});
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}
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void setAttributeItems(unsigned Attribute, unsigned IntValue,
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StringRef StringValue, bool OverwriteExisting) {
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// Look for existing attribute item.
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if (AttributeItem *Item = getAttributeItem(Attribute)) {
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if (!OverwriteExisting)
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return;
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Item->Type = AttributeType::NumericAndText;
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Item->IntValue = IntValue;
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Item->StringValue = std::string(StringValue);
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return;
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}
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// Create new attribute item.
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Contents.push_back({AttributeType::NumericAndText, Attribute, IntValue,
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std::string(StringValue)});
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}
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void emitAttribute(unsigned Attribute, unsigned Value) override;
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void emitTextAttribute(unsigned Attribute, StringRef String) override;
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void emitIntTextAttribute(unsigned Attribute, unsigned IntValue,
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StringRef StringValue) override;
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void finishAttributeSection() override;
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size_t calculateContentSize() const;
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public:
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MCELFStreamer &getStreamer();
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RISCVTargetELFStreamer(MCStreamer &S, const MCSubtargetInfo &STI);
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void emitDirectiveOptionPush() override;
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void emitDirectiveOptionPop() override;
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void emitDirectiveOptionPIC() override;
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void emitDirectiveOptionNoPIC() override;
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void emitDirectiveOptionRVC() override;
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void emitDirectiveOptionNoRVC() override;
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void emitDirectiveOptionRelax() override;
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void emitDirectiveOptionNoRelax() override;
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};
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MCELFStreamer *createRISCVELFStreamer(MCContext &C,
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std::unique_ptr<MCAsmBackend> MAB,
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std::unique_ptr<MCObjectWriter> MOW,
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std::unique_ptr<MCCodeEmitter> MCE,
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bool RelaxAll);
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}
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#endif
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