[lld-macho] Optimize bind opcodes with multiple passes
In D105866, we used an intermediate container to store a list of opcodes. Here,
we use that data structure to help us perform optimization passes that would allow
a more efficient encoding of bind opcodes. Currently, the functionality mirrors the
optimization pass {1,2} done in ld64 for bind opcodes under optimization gate
to prevent slight regressions.
Reviewed By: int3, #lld-macho
Differential Revision: https://reviews.llvm.org/D105867
This commit is contained in:
Vincent Lee
parent
c23da666b5
commit
d695d0d6f6
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@ -124,6 +124,7 @@ struct Configuration {
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uint32_t dylibCompatibilityVersion = 0;
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uint32_t dylibCurrentVersion = 0;
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uint32_t timeTraceGranularity = 500;
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unsigned optimize;
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std::string progName;
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// For `clang -arch arm64 -arch x86_64`, clang will:
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@ -1170,6 +1170,7 @@ bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
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symtab->addDynamicLookup(arg->getValue());
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config->mapFile = args.getLastArgValue(OPT_map);
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config->optimize = args::getInteger(args, OPT_O, 1);
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config->outputFile = args.getLastArgValue(OPT_o, "a.out");
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config->finalOutput =
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args.getLastArgValue(OPT_final_output, config->outputFile);
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@ -71,6 +71,8 @@ def lto_O: Joined<["--"], "lto-O">,
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def thinlto_cache_policy: Joined<["--"], "thinlto-cache-policy=">,
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HelpText<"Pruning policy for the ThinLTO cache">,
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Group<grp_lld>;
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def O : JoinedOrSeparate<["-"], "O">,
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HelpText<"Optimize output file size">;
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// This is a complete Options.td compiled from Apple's ld(1) manpage
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// dated 2018-03-07 and cross checked with ld64 source code in repo
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@ -282,6 +282,7 @@ struct BindIR {
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// scream instead of accidentally writing "valid" values.
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uint8_t opcode = 0xF0;
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uint64_t data = 0;
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uint64_t consecutiveCount = 0;
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};
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} // namespace
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@ -297,46 +298,77 @@ static void encodeBinding(const OutputSection *osec, uint64_t outSecOff,
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OutputSegment *seg = osec->parent;
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uint64_t offset = osec->getSegmentOffset() + outSecOff;
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if (lastBinding.segment != seg) {
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BindIR op = {
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static_cast<uint8_t>(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB |
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seg->index), // opcode
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offset // data
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};
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opcodes.push_back(op);
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opcodes.push_back(
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{static_cast<uint8_t>(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB |
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seg->index),
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offset});
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lastBinding.segment = seg;
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lastBinding.offset = offset;
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} else if (lastBinding.offset != offset) {
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BindIR op = {
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static_cast<uint8_t>(BIND_OPCODE_ADD_ADDR_ULEB), // opcode
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offset - lastBinding.offset // data
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};
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opcodes.push_back(op);
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opcodes.push_back({BIND_OPCODE_ADD_ADDR_ULEB, offset - lastBinding.offset});
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lastBinding.offset = offset;
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}
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if (lastBinding.addend != addend) {
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BindIR op = {
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static_cast<uint8_t>(BIND_OPCODE_SET_ADDEND_SLEB), // opcode
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static_cast<uint64_t>(addend) // data
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};
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opcodes.push_back(op);
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opcodes.push_back(
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{BIND_OPCODE_SET_ADDEND_SLEB, static_cast<uint64_t>(addend)});
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lastBinding.addend = addend;
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}
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BindIR op = {
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static_cast<uint8_t>(BIND_OPCODE_DO_BIND), // opcode
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0 // data
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};
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opcodes.push_back(op);
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opcodes.push_back({BIND_OPCODE_DO_BIND, 0});
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// DO_BIND causes dyld to both perform the binding and increment the offset
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lastBinding.offset += target->wordSize;
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}
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static void optimizeOpcodes(std::vector<BindIR> &opcodes) {
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// Pass 1: Combine bind/add pairs
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size_t i;
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int pWrite = 0;
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for (i = 1; i < opcodes.size(); ++i, ++pWrite) {
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if ((opcodes[i].opcode == BIND_OPCODE_ADD_ADDR_ULEB) &&
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(opcodes[i - 1].opcode == BIND_OPCODE_DO_BIND)) {
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opcodes[pWrite].opcode = BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB;
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opcodes[pWrite].data = opcodes[i].data;
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++i;
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} else {
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opcodes[pWrite] = opcodes[i - 1];
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}
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}
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if (i == opcodes.size())
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opcodes[pWrite] = opcodes[i - 1];
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opcodes.resize(pWrite + 1);
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// Pass 2: Compress two or more bind_add opcodes
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pWrite = 0;
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for (i = 1; i < opcodes.size(); ++i, ++pWrite) {
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if ((opcodes[i].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
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(opcodes[i - 1].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
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(opcodes[i].data == opcodes[i - 1].data)) {
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opcodes[pWrite].opcode = BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB;
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opcodes[pWrite].consecutiveCount = 2;
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opcodes[pWrite].data = opcodes[i].data;
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++i;
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while (i < opcodes.size() &&
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(opcodes[i].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
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(opcodes[i].data == opcodes[i - 1].data)) {
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opcodes[pWrite].consecutiveCount++;
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++i;
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}
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} else {
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opcodes[pWrite] = opcodes[i - 1];
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}
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}
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if (i == opcodes.size())
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opcodes[pWrite] = opcodes[i - 1];
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opcodes.resize(pWrite + 1);
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}
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static void flushOpcodes(const BindIR &op, raw_svector_ostream &os) {
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uint8_t opcode = op.opcode & BIND_OPCODE_MASK;
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switch (opcode) {
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case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB:
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case BIND_OPCODE_ADD_ADDR_ULEB:
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case BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB:
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os << op.opcode;
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encodeULEB128(op.data, os);
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break;
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@ -347,6 +379,11 @@ static void flushOpcodes(const BindIR &op, raw_svector_ostream &os) {
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case BIND_OPCODE_DO_BIND:
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os << op.opcode;
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break;
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case BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB:
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os << op.opcode;
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encodeULEB128(op.consecutiveCount, os);
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encodeULEB128(op.data, os);
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break;
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default:
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llvm_unreachable("cannot bind to an unrecognized symbol");
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}
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@ -446,6 +483,8 @@ void BindingSection::finalizeContents() {
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encodeBinding(b.target.isec->parent,
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b.target.isec->getOffset(b.target.offset), b.addend,
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lastBinding, opcodes);
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if (config->optimize > 1)
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optimizeOpcodes(opcodes);
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for (const auto &op : opcodes)
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flushOpcodes(op, os);
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}
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@ -478,6 +517,8 @@ void WeakBindingSection::finalizeContents() {
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encodeBinding(b.target.isec->parent,
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b.target.isec->getOffset(b.target.offset), b.addend,
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lastBinding, opcodes);
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if (config->optimize > 1)
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optimizeOpcodes(opcodes);
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for (const auto &op : opcodes)
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flushOpcodes(op, os);
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}
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@ -2,28 +2,83 @@
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# RUN: rm -rf %t; split-file %s %t
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test.s -o %t/test.o
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# RUN: %lld -dylib %t/foo.o -o %t/libfoo.dylib
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# RUN: %lld -lSystem %t/test.o %t/libfoo.dylib -o %t/test
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# RUN: %lld -O2 -dylib %t/foo.o -o %t/libfoo.dylib
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# RUN: %lld -O2 -lSystem %t/test.o %t/libfoo.dylib -o %t/test
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## Make sure we emit exactly one BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM per
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## symbol.
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# RUN: obj2yaml %t/test | FileCheck %s --implicit-check-not BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM
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## Test:
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## 1/ We emit exactly one BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM per symbol.
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## 2/ Combine BIND_OPCODE_DO_BIND and BIND_OPCODE_ADD_ADDR_ULEB pairs.
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## 3/ Compact BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB
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# RUN: obj2yaml %t/test | FileCheck %s
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# CHECK: Opcode: BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM
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# CHECK: BindOpcodes:
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: Symbol: _foo
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# CHECK: Opcode: BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_TYPE_IMM
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# CHECK-NEXT: Imm: 1
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_DYLIB_ORDINAL_IMM
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# CHECK-NEXT: Imm: 2
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB
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# CHECK-NEXT: Imm: 2
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# CHECK-NEXT: ULEBExtraData: [ 0x0 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ULEBExtraData: [ 0x2, 0x8 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_ADDEND_SLEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: SLEBExtraData: [ 1 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ULEBExtraData: [ 0x1008 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_ADDEND_SLEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: SLEBExtraData: [ 0 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: Symbol: _bar
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# CHECK-NEXT: Opcode: BIND_OPCODE_SET_TYPE_IMM
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# CHECK-NEXT: Imm: 1
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ULEBExtraData: [ 0xFFFFFFFFFFFFEFD0 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ULEBExtraData: [ 0x8 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ULEBExtraData: [ 0x1008 ]
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DO_BIND
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: Symbol: ''
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# CHECK-NEXT: Opcode: BIND_OPCODE_DONE
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: Symbol: ''
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# RUN: llvm-objdump --macho --bind %t/test | FileCheck %s --check-prefix=BIND
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# BIND: Bind table:
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# BIND-NEXT: segment section address type addend dylib symbol
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# BIND-NEXT: __DATA __data {{.*}} pointer 0 libfoo _foo
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# BIND-NEXT: __DATA __data {{.*}} pointer 0 libfoo _foo
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# BIND-NEXT: __DATA __data {{.*}} pointer 0 libfoo _bar
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# BIND-NEXT: __DATA __data {{.*}} pointer 0 libfoo _bar
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# BIND-NEXT: __DATA __data 0x100001000 pointer 0 libfoo _foo
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# BIND-NEXT: __DATA __data 0x100001010 pointer 0 libfoo _foo
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# BIND-NEXT: __DATA __data 0x100001020 pointer 1 libfoo _foo
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# BIND-NEXT: __DATA __data 0x100002030 pointer 0 libfoo _foo
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# BIND-NEXT: __DATA __data 0x100001008 pointer 0 libfoo _bar
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# BIND-NEXT: __DATA __data 0x100001018 pointer 0 libfoo _bar
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# BIND-NEXT: __DATA __data 0x100002028 pointer 0 libfoo _bar
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# BIND-EMPTY:
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#--- foo.s
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@ -39,6 +94,10 @@ _bar:
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.quad _bar
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.quad _foo
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.quad _bar
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.quad _foo+1
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.zero 0x1000
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.quad _bar
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.quad _foo
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.globl _main
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.text
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