[ELF] Linkerscript: remove repeated sections in LinkerScript<ELFT>::filter

[evgeny777]

Summary

Currently we can have more than one output section with the same name. The LinkerScript filter() method removes only first section found in name lookup.

[ruiu]

LGTM

ELF/LinkerScript.cpp

194

This is basically remove_if, so let's name removeIf.

ELF/LinkerScript.cpp

for (InputSectionBase<ELFT> *S : F->getSections())
       if (!isDiscarded(S) && !S->OutSec)
         addSection(Factory, *Out, S, getOutputSectionName(S));
 
   // Remove from the output all the sections which did not meet
   // the optional constraints.
   filter();
 }
 
+template <class R, class T>
+static inline void removeElements(R &Range, const T &Pred) {
+  Range.erase(std::remove_if(Range.begin(), Range.end(), Pred), Range.end());
+}
+
 // Process ONLY_IF_RO and ONLY_IF_RW.
 template <class ELFT> void LinkerScript<ELFT>::filter() {
   // In this loop, we remove output sections if they don't satisfy
   // requested properties.
   for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
     auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
     if (!Cmd || Cmd->Name == "/DISCARD/")
       continue;
 
     if (Cmd->Constraint == ConstraintKind::NoConstraint)
       continue;
 
-    auto It = llvm::find_if(*OutputSections, [&](OutputSectionBase<ELFT> *S) {
-      return S->getName() == Cmd->Name;
-    });
-    if (It == OutputSections->end())
-      continue;
-
-    OutputSectionBase<ELFT> *Sec = *It;
-    bool Writable = (Sec->getFlags() & SHF_WRITE);
+    removeElements(*OutputSections, [&](OutputSectionBase<ELFT> *S) {
+      bool Writable = (S->getFlags() & SHF_WRITE);
       bool RO = (Cmd->Constraint == ConstraintKind::ReadOnly);
       bool RW = (Cmd->Constraint == ConstraintKind::ReadWrite);
 
-    if ((RO && Writable) || (RW && !Writable))
-      OutputSections->erase(It);
+      return S->getName() == Cmd->Name &&
+             ((RO && Writable) || (RW && !Writable));
+    });
   }
 }
 
 template <class ELFT> void LinkerScript<ELFT>::assignAddresses() {
   ArrayRef<OutputSectionBase<ELFT> *> Sections = *OutputSections;
   // Orphan sections are sections present in the input files which
   // are not explicitly placed into the output file by the linker script.
   // We place orphan sections at end of file.

test/ELF/linkerscript/linkerscript-sections-constraint.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: echo "SECTIONS { \
 # RUN:  .writable : ONLY_IF_RW { *(.writable) } \
 # RUN:  .readable : ONLY_IF_RO { *(.readable) }}" > %t.script
 # RUN: ld.lld -o %t1 --script %t.script %t
 # RUN: llvm-objdump -section-headers %t1 | \
 # RUN:   FileCheck -check-prefix=BASE %s
 # BASE: Sections:
 # BASE-NEXT: Idx Name          Size      Address          Type
 # BASE-NEXT:   0               00000000 0000000000000000
-# BASE-NEXT:   1 .writable     00000004 0000000000000190 DATA
-# BASE-NEXT:   2 .readable     00000004 0000000000000194 DATA
+# BASE-NEXT:   1 .writable     00000004 0000000000000200 DATA
+# BASE-NEXT:   2 .readable     00000004 0000000000000204 DATA
 
 # RUN: echo "SECTIONS { \
 # RUN:  .writable : ONLY_IF_RO { *(.writable) } \
 # RUN:  .readable : ONLY_IF_RW { *(.readable) }}" > %t.script
 # RUN: ld.lld -o %t1 --script %t.script %t
 # RUN: llvm-objdump -section-headers %t1 | \
 # RUN:   FileCheck -check-prefix=NOSECTIONS %s
 # NOSECTIONS: Sections:
 # NOSECTIONS-NOT: .writable
 # NOSECTIONS-NOT: .readable
 
+# RUN: echo "SECTIONS { \
+# RUN:  .foo : ONLY_IF_RO { *(.foo.*) }}" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -section-headers %t1 | \
+# RUN:   FileCheck -check-prefix=NOSECTIONS2 %s
+# NOSECTIONS2: Sections:
+# NOSECTIONS2-NOT: .foo
+
 .global _start
 _start:
   nop
 
 .section .writable, "aw"
 writable:
  .long 1
 
 .section .readable, "a"
 readable:
  .long 2
+
+.section .foo.1, "awx"
+ .long 0
+
+.section .foo.2, "aw"
+ .long 0