diff options
| -rw-r--r-- | lld/ELF/LTO.cpp | 43 | ||||
| -rw-r--r-- | lld/ELF/Writer.cpp | 4 | ||||
| -rw-r--r-- | lld/test/ELF/lto/parallel-internalize.ll | 57 |
3 files changed, 81 insertions, 23 deletions
diff --git a/lld/ELF/LTO.cpp b/lld/ELF/LTO.cpp index bf9e1d2ba3c..9f2457f1277 100644 --- a/lld/ELF/LTO.cpp +++ b/lld/ELF/LTO.cpp @@ -106,13 +106,6 @@ void BitcodeCompiler::add(BitcodeFile &F) { SmallPtrSet<GlobalValue *, 8> Used; collectUsedGlobalVariables(M, Used, /* CompilerUsed */ false); - // This function is called if we know that the combined LTO object will - // provide a definition of a symbol. It undefines the symbol so that the - // definition in the combined LTO object will replace it when parsed. - auto Undefine = [](Symbol *S) { - replaceBody<Undefined>(S, S->body()->getName(), STV_DEFAULT, 0); - }; - for (const BasicSymbolRef &Sym : Obj->symbols()) { uint32_t Flags = Sym.getFlags(); GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl()); @@ -123,14 +116,30 @@ void BitcodeCompiler::add(BitcodeFile &F) { Symbol *S = Syms[BodyIndex++]; if (Flags & BasicSymbolRef::SF_Undefined) continue; - if (!GV) { - // Module asm symbol. - Undefine(S); - continue; - } auto *B = dyn_cast<DefinedBitcode>(S->body()); if (!B || B->File != &F) continue; + + // We collect the set of symbols we want to internalize here + // and change the linkage after the IRMover executed, i.e. after + // we imported the symbols and satisfied undefined references + // to it. We can't just change linkage here because otherwise + // the IRMover will just rename the symbol. + if (GV && shouldInternalize(Used, S, GV)) + InternalizedSyms.insert(GV->getName()); + + // At this point we know that either the combined LTO object will provide a + // definition of a symbol, or we will internalize it. In either case, we + // need to undefine the symbol. In the former case, the real definition + // needs to be able to replace the original definition without conflicting. + // In the latter case, we need to allow the combined LTO object to provide a + // definition with the same name, for example when doing parallel codegen. + replaceBody<Undefined>(S, S->body()->getName(), STV_DEFAULT, 0); + + if (!GV) + // Module asm symbol. + continue; + switch (GV->getLinkage()) { default: break; @@ -142,16 +151,6 @@ void BitcodeCompiler::add(BitcodeFile &F) { break; } - // We collect the set of symbols we want to internalize here - // and change the linkage after the IRMover executed, i.e. after - // we imported the symbols and satisfied undefined references - // to it. We can't just change linkage here because otherwise - // the IRMover will just rename the symbol. - if (shouldInternalize(Used, S, GV)) - InternalizedSyms.insert(GV->getName()); - else - Undefine(S); - Keep.push_back(GV); } diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp index 153c645c8f1..6937dd59f88 100644 --- a/lld/ELF/Writer.cpp +++ b/lld/ELF/Writer.cpp @@ -1391,7 +1391,9 @@ template <class ELFT> void Writer<ELFT>::createSections() { if (auto *SS = dyn_cast<SharedSymbol<ELFT>>(Body)) SS->File->IsUsed = true; - if (Body->isUndefined() && !S->isWeak()) + // We only report undefined symbols in regular objects. This means that we + // will accept an undefined reference in bitcode if it can be optimized out. + if (S->IsUsedInRegularObj && Body->isUndefined() && !S->isWeak()) reportUndefined<ELFT>(Symtab, Body); if (auto *C = dyn_cast<DefinedCommon>(Body)) diff --git a/lld/test/ELF/lto/parallel-internalize.ll b/lld/test/ELF/lto/parallel-internalize.ll new file mode 100644 index 00000000000..58ed50eab89 --- /dev/null +++ b/lld/test/ELF/lto/parallel-internalize.ll @@ -0,0 +1,57 @@ +; REQUIRES: x86 +; RUN: llvm-as -o %t.bc %s +; RUN: ld.lld -m elf_x86_64 --lto-jobs=2 -save-temps -o %t %t.bc -e foo --lto-O0 +; RUN: llvm-readobj -t -dyn-symbols %t | FileCheck %s +; RUN: llvm-nm %t0.lto.o | FileCheck --check-prefix=CHECK0 %s +; RUN: llvm-nm %t1.lto.o | FileCheck --check-prefix=CHECK1 %s + +; CHECK: Symbols [ +; CHECK-NEXT: Symbol { +; CHECK-NEXT: Name: (0) +; CHECK-NEXT: Value: 0x0 +; CHECK-NEXT: Size: 0 +; CHECK-NEXT: Binding: Local (0x0) +; CHECK-NEXT: Type: None (0x0) +; CHECK-NEXT: Other: 0 +; CHECK-NEXT: Section: Undefined (0x0) +; CHECK-NEXT: } +; CHECK-NEXT: Symbol { +; CHECK-NEXT: Name: bar (5) +; CHECK-NEXT: Value: 0x11010 +; CHECK-NEXT: Size: 8 +; CHECK-NEXT: Binding: Local (0x0) +; CHECK-NEXT: Type: Function (0x2) +; CHECK-NEXT: Other [ (0x2) +; CHECK-NEXT: STV_HIDDEN (0x2) +; CHECK-NEXT: ] +; CHECK-NEXT: Section: .text (0x2) +; CHECK-NEXT: } +; CHECK-NEXT: Symbol { +; CHECK-NEXT: Name: foo (1) +; CHECK-NEXT: Value: 0x11000 +; CHECK-NEXT: Size: 8 +; CHECK-NEXT: Binding: Global (0x1) +; CHECK-NEXT: Type: Function (0x2) +; CHECK-NEXT: Other: 0 +; CHECK-NEXT: Section: .text (0x2) +; CHECK-NEXT: } +; CHECK-NEXT: ] +; CHECK-NEXT: DynamicSymbols [ +; CHECK-NEXT: ] + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; CHECK0: U bar +; CHECK0: T foo +define void @foo() { + call void @bar() + ret void +} + +; CHECK1: T bar +; CHECK1: U foo +define void @bar() { + call void @foo() + ret void +} |
