Revert r319008, "[ELF] Do not keep symbols if they referenced only from discarded sections."

and r319051, "Add a missing test."

r319008 broke the LTO bots;
r319051 depends on changes in r319008.

llvm-svn: 319154

lld/ELF/MarkLive.cpp

@@ -64,12 +64,6 @@ static void resolveReloc(InputSectionBase &Sec, RelT &Rel,
                          std::function<void(InputSectionBase *, uint64_t)> Fn) {
   Symbol &B = Sec.getFile<ELFT>()->getRelocTargetSym(Rel);
 
-  // If a symbol is referenced in a live section, it is used.
-  B.Used = true;
-  if (auto *SS = dyn_cast<SharedSymbol>(&B))
-    if (!SS->isWeak())
-      SS->getFile<ELFT>()->IsNeeded = true;
-
   if (auto *D = dyn_cast<Defined>(&B)) {
     if (!D->Section)
       return;

lld/ELF/SymbolTable.cpp

@@ -305,8 +305,7 @@ Symbol *SymbolTable::addUndefined(StringRef Name, uint8_t Binding,
     S->Binding = Binding;
   if (Binding != STB_WEAK) {
     if (auto *SS = dyn_cast<SharedSymbol>(S))
-      if (!Config->GcSections)
-        SS->getFile<ELFT>()->IsNeeded = true;
+      SS->getFile<ELFT>()->IsNeeded = true;
   }
   if (auto *L = dyn_cast<Lazy>(S)) {
     // An undefined weak will not fetch archive members. See comment on Lazy in
@@ -501,7 +500,7 @@ void SymbolTable::addShared(StringRef Name, SharedFile<ELFT> *File,
                                 Alignment, Verdef);
     if (!WasInserted) {
       S->Binding = Binding;
-      if (!S->isWeak() && !Config->GcSections)
+      if (!S->isWeak())
         File->IsNeeded = true;
     }
   }

lld/ELF/Symbols.h

@@ -134,8 +134,8 @@ protected:
          uint8_t Type)
       : Binding(Binding), SymbolKind(K), NeedsPltAddr(false),
         IsInGlobalMipsGot(false), Is32BitMipsGot(false), IsInIplt(false),
-        IsInIgot(false), IsPreemptible(false), Used(!Config->GcSections),
-        Type(Type), StOther(StOther), Name(Name) {}
+        IsInIgot(false), IsPreemptible(false), Type(Type), StOther(StOther),
+        Name(Name) {}
 
   const unsigned SymbolKind : 8;
 
@@ -157,9 +157,6 @@ public:
 
   unsigned IsPreemptible : 1;
 
-  // True if an undefined or shared symbol is used from a live section.
-  unsigned Used : 1;
-
   // The following fields have the same meaning as the ELF symbol attributes.
   uint8_t Type;    // symbol type
   uint8_t StOther; // st_other field value

lld/ELF/Writer.cpp

@@ -448,9 +448,8 @@ static bool includeInSymtab(const Symbol &B) {
     if (auto *S = dyn_cast<MergeInputSection>(Sec))
       if (!S->getSectionPiece(D->Value)->Live)
         return false;
-    return true;
   }
-  return B.Used;
+  return true;
 }
 
 // Local symbols are not in the linker's symbol table. This function scans

lld/test/ELF/Inputs/gc-sections-shared2.s

@@ -1,3 +0,0 @@
-.global qux
-.type qux, @function
-qux:

lld/test/ELF/gc-collect-undefined.s

@@ -1,19 +0,0 @@
-# REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
-# RUN: ld.lld %t -o %tout --gc-sections -shared
-# RUN: llvm-nm -D %tout | FileCheck %s
-
-# CHECK-NOT: qux
-# CHECK: bar
-# CHECK-NOT: qux
-
-	.global foo,bar,qux
-	.local baz
-
-	.section .data.foo,"aw",%progbits
-foo:
-	.dc.a	bar
-
-	.section .bata.baz,"aw",%progbits
-baz:
-	.dc.a	qux

lld/test/ELF/gc-sections-shared.s

@@ -1,18 +1,14 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t2.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/gc-sections-shared.s -o %t3.o
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/gc-sections-shared2.s -o %t4.o
 # RUN: ld.lld -shared %t2.o -o %t2.so
 # RUN: ld.lld -shared %t3.o -o %t3.so
-# RUN: ld.lld -shared %t4.o -o %t4.so
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
-# RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t %t.o --as-needed %t2.so %t3.so %t4.so
+# RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t %t.o --as-needed %t2.so %t3.so
 # RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck %s
 
 # This test the property that we have a needed line for every undefined.
-# It would also be OK to keep bar2 and the need for %t2.so
-# At the same time, weak symbols should not cause adding DT_NEEDED;
-# this case is checked with symbol qux and %t4.so.
+# It would also be OK to drop bar2 and the need for the .so
 
 # CHECK:      DynamicSymbols [
 # CHECK-NEXT:   Symbol {
@@ -25,6 +21,15 @@
 # CHECK-NEXT:     Section: Undefined (0x0)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: bar2
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Global
+# CHECK-NEXT:     Type:
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: bar
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size:
@@ -43,15 +48,6 @@
 # CHECK-NEXT:     Section: .text
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: qux
-# CHECK-NEXT:     Value:
-# CHECK-NEXT:     Size:
-# CHECK-NEXT:     Binding: Weak
-# CHECK-NEXT:     Type:
-# CHECK-NEXT:     Other:
-# CHECK-NEXT:     Section: Undefined
-# CHECK-NEXT:   }
-# CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: baz
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size:
@@ -63,65 +59,10 @@
 # CHECK-NEXT: ]
 
 # CHECK-NOT: NEEDED
+# CHECK:     NEEDED Shared library: [{{.*}}2.so]
 # CHECK:     NEEDED Shared library: [{{.*}}3.so]
 # CHECK-NOT: NEEDED
 
-# Test with %t.o at the end too.
-# RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t --as-needed %t2.so %t3.so %t4.so %t.o
-# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck --check-prefix=CHECK2 %s
-
-# CHECK2:      DynamicSymbols [
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name:
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Local
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined (0x0)
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: bar
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: .text
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: qux
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Weak
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: foo
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: .text
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: baz
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined
-# CHECK2-NEXT:   }
-# CHECK2-NEXT: ]
-
-# CHECK2-NOT: NEEDED
-# CHECK2:     NEEDED Shared library: [{{.*}}3.so]
-# CHECK2-NOT: NEEDED
-
 .section .text.foo, "ax"
 .globl foo
 foo:
@@ -134,10 +75,8 @@ ret
 
 .section .text._start, "ax"
 .globl _start
-.weak qux
 _start:
 call baz
-call qux
 ret
 
 .section .text.unused, "ax"