[lld] r329787 - [ELF] - Reorder local symbols.
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 11 02:24:28 PDT 2018
Author: grimar
Date: Wed Apr 11 02:24:27 2018
New Revision: 329787
URL: http://llvm.org/viewvc/llvm-project?rev=329787&view=rev
Log:
[ELF] - Reorder local symbols.
This fixes PR36716 (https://bugs.llvm.org/show_bug.cgi?id=36716),
Patch sorts local symbols to match the
following order: file1, local1, hidden1, file2, local2, hidden2 ...
Differential revision: https://reviews.llvm.org/D45325
Modified:
lld/trunk/ELF/SyntheticSections.cpp
lld/trunk/ELF/Writer.cpp
lld/trunk/test/ELF/local-symbols-order.s
lld/trunk/test/ELF/relocatable-comdat-multiple.s
Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=329787&r1=329786&r2=329787&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Wed Apr 11 02:24:27 2018
@@ -1545,16 +1545,35 @@ void SymbolTableBaseSection::finalizeCon
// The ELF spec requires that all local symbols precede global symbols, so we
// sort symbol entries in this function. (For .dynsym, we don't do that because
// symbols for dynamic linking are inherently all globals.)
+//
+// Aside from above, we put local symbols in groups starting with the STT_FILE
+// symbol. That is convenient for purpose of identifying where are local symbols
+// coming from.
void SymbolTableBaseSection::postThunkContents() {
if (this->Type == SHT_DYNSYM)
return;
- // move all local symbols before global symbols.
- auto It = std::stable_partition(
+
+ // Move all local symbols before global symbols.
+ auto E = std::stable_partition(
Symbols.begin(), Symbols.end(), [](const SymbolTableEntry &S) {
return S.Sym->isLocal() || S.Sym->computeBinding() == STB_LOCAL;
});
- size_t NumLocals = It - Symbols.begin();
+ size_t NumLocals = E - Symbols.begin();
getParent()->Info = NumLocals + 1;
+
+ // Assign the growing unique ID for each local symbol's file.
+ DenseMap<InputFile *, unsigned> FileIDs;
+ for (auto I = Symbols.begin(); I != E; ++I)
+ FileIDs.insert({I->Sym->File, FileIDs.size()});
+
+ // Sort the local symbols to group them by file. We do not need to care about
+ // the STT_FILE symbols, they are already naturally placed first in each group.
+ // That happens because STT_FILE is always the first symbol in the object and
+ // hence precede all other local symbols we add for a file.
+ std::stable_sort(Symbols.begin(), E,
+ [&](const SymbolTableEntry &L, const SymbolTableEntry &R) {
+ return FileIDs[L.Sym->File] < FileIDs[R.Sym->File];
+ });
}
void SymbolTableBaseSection::addSymbol(Symbol *B) {
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=329787&r1=329786&r2=329787&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Wed Apr 11 02:24:27 2018
@@ -1673,15 +1673,15 @@ template <class ELFT> void Writer<ELFT>:
} while (Changed);
}
+ // createThunks may have added local symbols to the static symbol table
+ applySynthetic({InX::SymTab},
+ [](SyntheticSection *SS) { SS->postThunkContents(); });
+
// Fill other section headers. The dynamic table is finalized
// at the end because some tags like RELSZ depend on result
// of finalizing other sections.
for (OutputSection *Sec : OutputSections)
Sec->finalize<ELFT>();
-
- // createThunks may have added local symbols to the static symbol table
- applySynthetic({InX::SymTab},
- [](SyntheticSection *SS) { SS->postThunkContents(); });
}
// The linker is expected to define SECNAME_start and SECNAME_end
Modified: lld/trunk/test/ELF/local-symbols-order.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/local-symbols-order.s?rev=329787&r1=329786&r2=329787&view=diff
==============================================================================
--- lld/trunk/test/ELF/local-symbols-order.s (original)
+++ lld/trunk/test/ELF/local-symbols-order.s Wed Apr 11 02:24:27 2018
@@ -1,22 +1,32 @@
# REQUIRES: x86
-# RUN: echo '.file "file2"; foo2:; .global bar2; .hidden bar2; bar2:' > %t2.s
+# RUN: echo '.data; .file "file2"; foo2:; .global bar2; .hidden bar2; bar2:' > %t2.s
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %t2.s -o %t2.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
-# RUN: ld.lld -o %t %t1.o %t2.o
-# RUN: llvm-readobj -symbols -elf-output-style=GNU %t | FileCheck %s
+# RUN: ld.lld -o %t %t1.o %t2.o --emit-relocs
+# RUN: llvm-readobj -symbols -sections -elf-output-style=GNU %t | FileCheck %s
-## Show the order of the local symbols produced currently by LLD.
+## Check we sort local symbols to match the following order:
+## file1, local1, section1, hidden1, file2, local2, section2, hidden2 ...
+
+# CHECK: Section Headers:
+# CHECK: [Nr] Name
+# CHECK: [ [[ST:.*]]] .text
+# CHECK: [ [[SD:.*]]] .data
+# CHECK: [ [[SC:.*]]] .comment
# CHECK: Num: Value Size Type Bind Vis Ndx Name
# CHECK-NEXT: 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
# CHECK-NEXT: 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS file1
# CHECK-NEXT: 2: 0000000000201000 0 NOTYPE LOCAL DEFAULT 1 foo1
-# CHECK-NEXT: 3: 0000000000000000 0 FILE LOCAL DEFAULT ABS file2
-# CHECK-NEXT: 4: 0000000000201000 0 NOTYPE LOCAL DEFAULT 1 foo2
-# CHECK-NEXT: 5: 0000000000201000 0 NOTYPE LOCAL HIDDEN 1 bar1
-# CHECK-NEXT: 6: 0000000000201000 0 NOTYPE LOCAL HIDDEN 1 bar2
+# CHECK-NEXT: 3: 0000000000201000 0 SECTION LOCAL DEFAULT [[ST]]
+# CHECK-NEXT: 4: 0000000000201000 0 NOTYPE LOCAL HIDDEN 1 bar1
+# CHECK-NEXT: 5: 0000000000000000 0 FILE LOCAL DEFAULT ABS file2
+# CHECK-NEXT: 6: 0000000000201000 0 NOTYPE LOCAL DEFAULT 2 foo2
+# CHECK-NEXT: 7: 0000000000201000 0 SECTION LOCAL DEFAULT [[SD]]
+# CHECK-NEXT: 8: 0000000000201000 0 NOTYPE LOCAL HIDDEN 2 bar2
+# CHECK-NEXT: 9: 0000000000000000 0 SECTION LOCAL DEFAULT [[SC]]
foo1:
Modified: lld/trunk/test/ELF/relocatable-comdat-multiple.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/relocatable-comdat-multiple.s?rev=329787&r1=329786&r2=329787&view=diff
==============================================================================
--- lld/trunk/test/ELF/relocatable-comdat-multiple.s (original)
+++ lld/trunk/test/ELF/relocatable-comdat-multiple.s Wed Apr 11 02:24:27 2018
@@ -21,7 +21,7 @@
# CHECK-NEXT: Name: .group
# CHECK-NEXT: Index: 5
# CHECK-NEXT: Link: 8
-# CHECK-NEXT: Info: 2
+# CHECK-NEXT: Info: 6
# CHECK-NEXT: Type: COMDAT
# CHECK-NEXT: Signature: bbb
# CHECK-NEXT: Section(s) in group [
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