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-rw-r--r--lld/ELF/InputSection.cpp9
-rw-r--r--lld/ELF/InputSection.h15
-rw-r--r--lld/ELF/MarkLive.cpp2
-rw-r--r--lld/ELF/OutputSections.cpp4
-rw-r--r--lld/ELF/OutputSections.h3
-rw-r--r--lld/ELF/Writer.cpp9
-rw-r--r--lld/test/ELF/string-gc.s54
7 files changed, 85 insertions, 11 deletions
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 6737c2d8367..41703fb73b3 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -419,7 +419,8 @@ MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F,
StringRef Data((const char *)D.data(), D.size());
std::vector<std::pair<uintX_t, uintX_t>> &Offsets = this->Offsets;
- uintX_t V = Config->GcSections ? -1 : 0;
+ uintX_t V = Config->GcSections ? MergeInputSection<ELFT>::PieceDead
+ : MergeInputSection<ELFT>::PieceLive;
if (Header->sh_flags & SHF_STRINGS) {
uintX_t Offset = 0;
while (!Data.empty()) {
@@ -478,15 +479,15 @@ typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) {
// Compute the Addend and if the Base is cached, return.
uintX_t Addend = Offset - Start;
uintX_t &Base = I->second;
- if (Base != uintX_t(-1))
+ auto *MOS = static_cast<MergeOutputSection<ELFT> *>(this->OutSec);
+ if (!MOS->shouldTailMerge())
return Base + Addend;
// Map the base to the offset in the output section and cache it.
ArrayRef<uint8_t> D = this->getSectionData();
StringRef Data((const char *)D.data(), D.size());
StringRef Entry = Data.substr(Start, End - Start);
- Base =
- static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Entry);
+ Base = MOS->getOffset(Entry);
return Base + Addend;
}
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
index 908375f1a63..ea8fd438cdf 100644
--- a/lld/ELF/InputSection.h
+++ b/lld/ELF/InputSection.h
@@ -144,9 +144,22 @@ public:
typename InputSectionBase<ELFT>::Kind SectionKind);
// For each piece of data, we maintain the offsets in the input section and
- // in the output section. The latter may be -1 if it is not assigned yet.
+ // in the output section.
std::vector<std::pair<uintX_t, uintX_t>> Offsets;
+ // Merge input sections may use the following special values as the output
+ // section offset:
+ enum {
+ // The piece is dead.
+ PieceDead = uintX_t(-1),
+ // The piece is live, and an offset has not yet been assigned. After offsets
+ // have been assigned, if the output section uses tail merging, the field
+ // will still have this value and the output section offset is available
+ // from MergeOutputSection<ELFT>::getOffset(). Otherwise, this value has no
+ // special significance, it just means that the offset is 0.
+ PieceLive = uintX_t(0),
+ };
+
std::pair<std::pair<uintX_t, uintX_t> *, uintX_t>
getRangeAndSize(uintX_t Offset);
};
diff --git a/lld/ELF/MarkLive.cpp b/lld/ELF/MarkLive.cpp
index 5b20ccca047..f8000007913 100644
--- a/lld/ELF/MarkLive.cpp
+++ b/lld/ELF/MarkLive.cpp
@@ -143,7 +143,7 @@ template <class ELFT> void elf::markLive() {
if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(R.Sec)) {
std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
MS->getRangeAndSize(R.Offset);
- T.first->second = 0;
+ T.first->second = MergeInputSection<ELFT>::PieceLive;
}
if (R.Sec->Live)
return;
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 50108de6845..c3c9672e708 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -1271,7 +1271,7 @@ void MergeOutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
if (this->Header.sh_flags & SHF_STRINGS) {
for (unsigned I = 0, N = Offsets.size(); I != N; ++I) {
auto &P = Offsets[I];
- if (P.second == (uintX_t)-1)
+ if (P.second == MergeInputSection<ELFT>::PieceDead)
continue;
uintX_t Start = P.first;
@@ -1279,7 +1279,7 @@ void MergeOutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
StringRef Entry = Data.substr(Start, End - Start);
uintX_t OutputOffset = Builder.add(Entry);
if (shouldTailMerge())
- OutputOffset = -1;
+ OutputOffset = MergeInputSection<ELFT>::PieceLive;
P.second = OutputOffset;
}
return;
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 1a305fbf1b0..d8c0e5b7484 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -310,8 +310,6 @@ template <class ELFT>
class MergeOutputSection final : public OutputSectionBase<ELFT> {
typedef typename ELFT::uint uintX_t;
- bool shouldTailMerge() const;
-
public:
MergeOutputSection(StringRef Name, uint32_t Type, uintX_t Flags,
uintX_t Alignment);
@@ -319,6 +317,7 @@ public:
void writeTo(uint8_t *Buf) override;
unsigned getOffset(StringRef Val);
void finalize() override;
+ bool shouldTailMerge() const;
private:
llvm::StringTableBuilder Builder;
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 63ed12a64e1..a590827c2e0 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1118,9 +1118,16 @@ template <class ELFT> static bool includeInSymtab(const SymbolBody &B) {
return false;
if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B)) {
+ // Always include absolute symbols.
+ if (!D->Section)
+ return true;
// Exclude symbols pointing to garbage-collected sections.
- if (D->Section && !D->Section->Live)
+ if (!D->Section->Live)
return false;
+ if (auto *S = dyn_cast<MergeInputSection<ELFT>>(D->Section))
+ if (S->getRangeAndSize(D->Value).first->second ==
+ MergeInputSection<ELFT>::PieceDead)
+ return false;
}
return true;
}
diff --git a/lld/test/ELF/string-gc.s b/lld/test/ELF/string-gc.s
new file mode 100644
index 00000000000..b6b1e868f5d
--- /dev/null
+++ b/lld/test/ELF/string-gc.s
@@ -0,0 +1,54 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld %t.o -o %t --gc-sections
+// RUN: llvm-readobj -symbols %t | FileCheck %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: s1 (8)
+// CHECK-NEXT: Value: 0x10120
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Local (0x0)
+// CHECK-NEXT: Type: Object (0x1)
+// CHECK-NEXT: Other [ (0x2)
+// CHECK-NEXT: STV_HIDDEN (0x2)
+// CHECK-NEXT: ]
+// CHECK-NEXT: Section: .rodata (0x1)
+// CHECK-NEXT: }
+// CHECK-NEXT: Symbol {
+// CHECK-NEXT: Name: _start (1)
+// CHECK-NEXT: Value: 0x11000
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Global (0x1)
+// CHECK-NEXT: Type: Function (0x2)
+// CHECK-NEXT: Other: 0
+// CHECK-NEXT: Section: .text (0x2)
+// CHECK-NEXT: }
+// CHECK-NEXT: ]
+
+.text
+.globl _start
+.type _start,@function
+_start:
+movl $s1, %eax
+
+.hidden s1
+.type s1,@object
+.section .rodata.str1.1,"aMS",@progbits,1
+.globl s1
+s1:
+.asciz "abcd"
+
+.hidden s2
+.type s2,@object
+.globl s2
+s2:
+.asciz "efgh"
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