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AArch64: add stubs to support long function calls on MCJIT

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As with global accesses, external functions could exist anywhere in
memory. Therefore the stub must create a complete 64-bit address. This
patch implements the fragment as (roughly):
    movz x16, #:abs_g3:somefunc
    movk x16, #:abs_g2_nc:somefunc
    movk x16, #:abs_g1_nc:somefunc
    movk x16, #:abs_g0_nc:somefunc
    br x16

In principle we could save 4 bytes by using a literal-load instead,
but it is unclear that would be more efficient and can only be tested
when real hardware is readily available.

This allows (for example) the MCJIT test 2003-05-07-ArgumentTest to
pass on AArch64.

llvm-svn: 181133
This commit is contained in:
Tim Northover 2013-05-04 20:14:09 +00:00
parent 71cd109478
commit 41e94642a9
3 changed files with 84 additions and 2 deletions
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20
lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
View File

@ -336,7 +336,25 @@ void RuntimeDyldImpl::addRelocationForSymbol(const RelocationEntry &RE,
}
uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr) {
if (Arch == Triple::arm) {
if (Arch == Triple::aarch64) {
// This stub has to be able to access the full address space,
// since symbol lookup won't necessarily find a handy, in-range,
// PLT stub for functions which could be anywhere.
uint32_t *StubAddr = (uint32_t*)Addr;
// Stub can use ip0 (== x16) to calculate address
*StubAddr = 0xd2e00010; // movz ip0, #:abs_g3:<addr>
StubAddr++;
*StubAddr = 0xf2c00010; // movk ip0, #:abs_g2_nc:<addr>
StubAddr++;
*StubAddr = 0xf2a00010; // movk ip0, #:abs_g1_nc:<addr>
StubAddr++;
*StubAddr = 0xf2800010; // movk ip0, #:abs_g0_nc:<addr>
StubAddr++;
*StubAddr = 0xd61f0200; // br ip0
return Addr;
} else if (Arch == Triple::arm) {
// TODO: There is only ARM far stub now. We should add the Thumb stub,
// and stubs for branches Thumb - ARM and ARM - Thumb.
uint32_t *StubAddr = (uint32_t*)Addr;

64
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
View File

@ -296,6 +296,19 @@ void RuntimeDyldELF::resolveAArch64Relocation(const SectionEntry &Section,
*TargetPtr = static_cast<uint32_t>(Result & 0xffffffffU);
break;
}
case ELF::R_AARCH64_CALL26: // fallthrough
case ELF::R_AARCH64_JUMP26: {
// Operation: S+A-P. Set Call or B immediate value to bits fff_fffc of the
// calculation.
uint64_t BranchImm = Value + Addend - FinalAddress;
// "Check that -2^27 <= result < 2^27".
assert(-(1LL << 27) <= static_cast<int64_t>(BranchImm) &&
static_cast<int64_t>(BranchImm) < (1LL << 27));
// Immediate goes in bits 25:0 of B and BL.
*TargetPtr |= static_cast<uint32_t>(BranchImm & 0xffffffcU) >> 2;
break;
}
case ELF::R_AARCH64_MOVW_UABS_G3: {
uint64_t Result = Value + Addend;
// Immediate goes in bits 20:5 of MOVZ/MOVK instruction
@ -775,7 +788,56 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
DEBUG(dbgs() << "\t\tSectionID: " << SectionID
<< " Offset: " << Offset
<< "\n");
if (Arch == Triple::arm &&
if (Arch == Triple::aarch64 &&
(RelType == ELF::R_AARCH64_CALL26 ||
RelType == ELF::R_AARCH64_JUMP26)) {
// This is an AArch64 branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is an AArch64 branch relocation.");
SectionEntry &Section = Sections[SectionID];
// Look for an existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
resolveRelocation(Section, Offset,
(uint64_t)Section.Address + i->second, RelType, 0);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr = createStubFunction(Section.Address +
Section.StubOffset);
RelocationEntry REmovz_g3(SectionID,
StubTargetAddr - Section.Address,
ELF::R_AARCH64_MOVW_UABS_G3, Value.Addend);
RelocationEntry REmovk_g2(SectionID,
StubTargetAddr - Section.Address + 4,
ELF::R_AARCH64_MOVW_UABS_G2_NC, Value.Addend);
RelocationEntry REmovk_g1(SectionID,
StubTargetAddr - Section.Address + 8,
ELF::R_AARCH64_MOVW_UABS_G1_NC, Value.Addend);
RelocationEntry REmovk_g0(SectionID,
StubTargetAddr - Section.Address + 12,
ELF::R_AARCH64_MOVW_UABS_G0_NC, Value.Addend);
if (Value.SymbolName) {
addRelocationForSymbol(REmovz_g3, Value.SymbolName);
addRelocationForSymbol(REmovk_g2, Value.SymbolName);
addRelocationForSymbol(REmovk_g1, Value.SymbolName);
addRelocationForSymbol(REmovk_g0, Value.SymbolName);
} else {
addRelocationForSection(REmovz_g3, Value.SectionID);
addRelocationForSection(REmovk_g2, Value.SectionID);
addRelocationForSection(REmovk_g1, Value.SectionID);
addRelocationForSection(REmovk_g0, Value.SectionID);
}
resolveRelocation(Section, Offset,
(uint64_t)Section.Address + Section.StubOffset,
RelType, 0);
Section.StubOffset += getMaxStubSize();
}
} else if (Arch == Triple::arm &&
(RelType == ELF::R_ARM_PC24 ||
RelType == ELF::R_ARM_CALL ||
RelType == ELF::R_ARM_JUMP24)) {

2
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
View File

@ -166,6 +166,8 @@ protected:
Triple::ArchType Arch;
inline unsigned getMaxStubSize() {
if (Arch == Triple::aarch64)
return 20; // movz; movk; movk; movk; br
if (Arch == Triple::arm || Arch == Triple::thumb)
return 8; // 32-bit instruction and 32-bit address
else if (Arch == Triple::mipsel || Arch == Triple::mips)