forked from OSchip/llvm-project
[ARM] Support .reloc *, R_ARM_NONE, *
R_ARM_NONE can be used to create references among sections. When --gc-sections is used, the referenced section will be retained if the origin section is retained. Add a generic MCFixupKind FK_NONE as this kind of no-op relocation is ubiquitous on ELF and COFF, and probably available on many other binary formats. See D62014. Reviewed By: peter.smith Differential Revision: https://reviews.llvm.org/D61992 llvm-svn: 360980
This commit is contained in:
Fangrui Song
parent
a74d654374
commit
43ca0e9eb8
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@ -20,7 +20,8 @@ class MCExpr;
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/// Extensible enumeration to represent the type of a fixup.
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enum MCFixupKind {
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FK_Data_1 = 0, ///< A one-byte fixup.
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FK_NONE = 0, ///< A no-op fixup.
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FK_Data_1, ///< A one-byte fixup.
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FK_Data_2, ///< A two-byte fixup.
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FK_Data_4, ///< A four-byte fixup.
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FK_Data_8, ///< A eight-byte fixup.
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@ -64,6 +64,7 @@ Optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
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const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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static const MCFixupKindInfo Builtins[] = {
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{"FK_NONE", 0, 0, 0},
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{"FK_Data_1", 0, 8, 0},
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{"FK_Data_2", 0, 16, 0},
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{"FK_Data_4", 0, 32, 0},
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@ -46,6 +46,13 @@ public:
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};
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} // end anonymous namespace
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Optional<MCFixupKind> ARMAsmBackend::getFixupKind(StringRef Name) const {
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if (STI.getTargetTriple().isOSBinFormatELF() && Name == "R_ARM_NONE")
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return FK_NONE;
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return MCAsmBackend::getFixupKind(Name);
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}
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const MCFixupKindInfo &ARMAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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const static MCFixupKindInfo InfosLE[ARM::NumTargetFixupKinds] = {
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// This table *must* be in the order that the fixup_* kinds are defined in
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@ -383,6 +390,7 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCAssembler &Asm,
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default:
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Ctx.reportError(Fixup.getLoc(), "bad relocation fixup type");
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return 0;
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case FK_NONE:
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case FK_Data_1:
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case FK_Data_2:
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case FK_Data_4:
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@ -761,7 +769,9 @@ bool ARMAsmBackend::shouldForceRelocation(const MCAssembler &Asm,
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const MCSymbolRefExpr *A = Target.getSymA();
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const MCSymbol *Sym = A ? &A->getSymbol() : nullptr;
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const unsigned FixupKind = Fixup.getKind() ;
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if ((unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_bl) {
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if (FixupKind == FK_NONE)
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return true;
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if (FixupKind == ARM::fixup_arm_thumb_bl) {
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assert(Sym && "How did we resolve this?");
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// If the symbol is external the linker will handle it.
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@ -803,6 +813,9 @@ static unsigned getFixupKindNumBytes(unsigned Kind) {
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default:
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llvm_unreachable("Unknown fixup kind!");
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case FK_NONE:
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return 0;
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case FK_Data_1:
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case ARM::fixup_arm_thumb_bcc:
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case ARM::fixup_arm_thumb_cp:
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@ -857,6 +870,9 @@ static unsigned getFixupKindContainerSizeBytes(unsigned Kind) {
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default:
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llvm_unreachable("Unknown fixup kind!");
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case FK_NONE:
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return 0;
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case FK_Data_1:
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return 1;
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case FK_Data_2:
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@ -37,6 +37,8 @@ public:
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// different.
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bool hasNOP() const { return STI.getFeatureBits()[ARM::HasV6T2Ops]; }
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Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
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const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
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bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
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@ -143,6 +143,8 @@ unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
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default:
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Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol");
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return ELF::R_ARM_NONE;
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case FK_NONE:
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return ELF::R_ARM_NONE;
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case FK_Data_1:
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switch (Modifier) {
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default:
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@ -302,7 +302,7 @@ void MipsAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
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Optional<MCFixupKind> MipsAsmBackend::getFixupKind(StringRef Name) const {
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return StringSwitch<Optional<MCFixupKind>>(Name)
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.Case("R_MIPS_NONE", (MCFixupKind)Mips::fixup_Mips_NONE)
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.Case("R_MIPS_NONE", FK_NONE)
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.Case("R_MIPS_32", FK_Data_4)
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.Case("R_MIPS_GOT_PAGE", (MCFixupKind)Mips::fixup_Mips_GOT_PAGE)
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.Case("R_MIPS_CALL_HI16", (MCFixupKind)Mips::fixup_Mips_CALL_HI16)
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@ -350,7 +350,6 @@ getFixupKindInfo(MCFixupKind Kind) const {
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// MipsFixupKinds.h.
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//
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// name offset bits flags
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{ "fixup_Mips_NONE", 0, 0, 0 },
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{ "fixup_Mips_16", 0, 16, 0 },
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{ "fixup_Mips_32", 0, 32, 0 },
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{ "fixup_Mips_REL32", 0, 32, 0 },
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@ -430,7 +429,6 @@ getFixupKindInfo(MCFixupKind Kind) const {
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// MipsFixupKinds.h.
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//
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// name offset bits flags
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{ "fixup_Mips_NONE", 0, 0, 0 },
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{ "fixup_Mips_16", 16, 16, 0 },
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{ "fixup_Mips_32", 0, 32, 0 },
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{ "fixup_Mips_REL32", 0, 32, 0 },
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@ -222,7 +222,7 @@ unsigned MipsELFObjectWriter::getRelocType(MCContext &Ctx,
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unsigned Kind = (unsigned)Fixup.getKind();
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switch (Kind) {
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case Mips::fixup_Mips_NONE:
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case FK_NONE:
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return ELF::R_MIPS_NONE;
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case FK_Data_1:
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Ctx.reportError(Fixup.getLoc(),
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@ -22,11 +22,8 @@ namespace Mips {
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// in MipsAsmBackend.cpp.
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//
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enum Fixups {
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// Branch fixups resulting in R_MIPS_NONE.
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fixup_Mips_NONE = FirstTargetFixupKind,
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// Branch fixups resulting in R_MIPS_16.
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fixup_Mips_16,
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fixup_Mips_16 = FirstTargetFixupKind,
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// Pure 32 bit data fixup resulting in - R_MIPS_32.
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fixup_Mips_32,
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@ -0,0 +1,37 @@
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# RUN: llvm-mc -triple=armv7-linux-gnueabi %s | FileCheck --check-prefix=PRINT %s
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# RUN: llvm-mc -triple=armv7eb-linux-gnueabi %s | FileCheck --check-prefix=PRINT %s
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# RUN: llvm-mc -filetype=obj -triple=armv7-linux-gnueabi %s -o %t
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# RUN: llvm-readobj -r %t | FileCheck %s
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# RUN: llvm-readelf -x .data %t | FileCheck --check-prefix=HEX %s
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# RUN: llvm-mc -filetype=obj -triple=armv7eb-linux-gnueabi %s -o %t
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# RUN: llvm-readobj -r %t | FileCheck %s
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# RUN: llvm-readelf -x .data %t | FileCheck --check-prefix=HEX %s
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.text
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bx lr
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nop
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nop
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.reloc 8, R_ARM_NONE, .data
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.reloc 4, R_ARM_NONE, foo+4
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.reloc 0, R_ARM_NONE, 8
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.data
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.globl foo
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foo:
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.word 0
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.word 0
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.word 0
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# PRINT: .reloc 8, R_ARM_NONE, .data
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# PRINT: .reloc 4, R_ARM_NONE, foo+4
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# PRINT: .reloc 0, R_ARM_NONE, 8
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# ARM relocations use the Elf32_Rel format. Addends are neither stored in the
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# relocation entries nor applied in the referenced locations.
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# CHECK: 0x8 R_ARM_NONE .data 0x0
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# CHECK-NEXT: 0x4 R_ARM_NONE foo 0x0
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# CHECK-NEXT: 0x0 R_ARM_NONE - 0x0
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# HEX: 0x00000000 00000000 00000000
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