[lld] r264048 - Skip some relocations in scanRelocs.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Tue Mar 22 08:24:29 2016
New Revision: 264048

URL: http://llvm.org/viewvc/llvm-project?rev=264048&view=rev
Log:
Skip some relocations in scanRelocs.

When a tls access is optimized, a group of relocations is converted at a
time.

We were already skipping relocations that were optimized out in
relocate, but not in scanRelocs.

This is a small optimization. I got here while working on a patch that
will always keep scanRelocs and relocate in sync.

Modified:
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/ELF/tls-opt-gdie.s

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=264048&r1=264047&r2=264048&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Mar 22 08:24:29 2016
@@ -258,21 +258,22 @@ template <bool Is64Bits> struct DenseMap
 };
 }
 
+// Returns the number of relocations processed.
 template <class ELFT, class RelT>
-static bool handleTlsRelocation(uint32_t Type, SymbolBody &Body,
-                                InputSectionBase<ELFT> &C, RelT &RI) {
+static unsigned handleTlsRelocation(uint32_t Type, SymbolBody &Body,
+                                    InputSectionBase<ELFT> &C, RelT &RI) {
   if (Target->pointsToLocalDynamicGotEntry(Type)) {
     if (Target->canRelaxTls(Type, nullptr))
-      return true;
+      return 1;
     if (Out<ELFT>::Got->addTlsIndex())
       Out<ELFT>::RelaDyn->addReloc({Target->TlsModuleIndexRel,
                                     DynamicReloc<ELFT>::Off_LTlsIndex,
                                     nullptr});
-    return true;
+    return 1;
   }
 
   if (!Body.IsTls)
-    return false;
+    return 0;
 
   if (Target->isTlsGlobalDynamicRel(Type)) {
     if (!Target->canRelaxTls(Type, &Body)) {
@@ -283,12 +284,16 @@ static bool handleTlsRelocation(uint32_t
         Out<ELFT>::RelaDyn->addReloc(
             {Target->TlsOffsetRel, DynamicReloc<ELFT>::Off_GTlsOffset, &Body});
       }
-      return true;
+      return 1;
     }
     if (!Body.isPreemptible())
-      return true;
+      return 1;
+    Out<ELFT>::Got->addEntry(Body);
+    Out<ELFT>::RelaDyn->addReloc(
+        {Target->TlsGotRel, DynamicReloc<ELFT>::Off_Got, false, &Body});
+    return 2;
   }
-  return false;
+  return 0;
 }
 
 // The reason we have to do this early scan is as follows
@@ -309,7 +314,8 @@ template <class RelTy>
 void Writer<ELFT>::scanRelocs(InputSectionBase<ELFT> &C,
                               iterator_range<const RelTy *> Rels) {
   const elf::ObjectFile<ELFT> &File = *C.getFile();
-  for (const RelTy &RI : Rels) {
+  for (auto I = Rels.begin(), E = Rels.end(); I != E; ++I) {
+    const RelTy &RI = *I;
     uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
     SymbolBody &OrigBody = File.getSymbolBody(SymIndex);
     SymbolBody &Body = OrigBody.repl();
@@ -328,8 +334,10 @@ void Writer<ELFT>::scanRelocs(InputSecti
         S->File->IsUsed = true;
 
     bool Preemptible = Body.isPreemptible();
-    if (handleTlsRelocation<ELFT>(Type, Body, C, RI))
+    if (unsigned Processed = handleTlsRelocation<ELFT>(Type, Body, C, RI)) {
+      I += (Processed - 1);
       continue;
+    }
 
     if (Target->needsDynRelative(Type))
       Out<ELFT>::RelaDyn->addReloc({Target->RelativeRel, &C, RI.r_offset, true,

Modified: lld/trunk/test/ELF/tls-opt-gdie.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/tls-opt-gdie.s?rev=264048&r1=264047&r2=264048&view=diff
==============================================================================
--- lld/trunk/test/ELF/tls-opt-gdie.s (original)
+++ lld/trunk/test/ELF/tls-opt-gdie.s Tue Mar 22 08:24:29 2016
@@ -6,15 +6,15 @@
 // RUN: llvm-objdump -d %t1 | FileCheck --check-prefix=DISASM %s
 
 //RELOC:      Section {
-//RELOC:      Index: 9
-//RELOC-NEXT: Name: .got
+//RELOC:      Index:
+//RELOC:      Name: .got
 //RELOC-NEXT: Type: SHT_PROGBITS
 //RELOC-NEXT: Flags [
 //RELOC-NEXT:   SHF_ALLOC
 //RELOC-NEXT:   SHF_WRITE
 //RELOC-NEXT: ]
-//RELOC-NEXT: Address: 0x120F0
-//RELOC-NEXT: Offset: 0x20F0
+//RELOC-NEXT: Address: 0x120B0
+//RELOC-NEXT: Offset: 0x20B0
 //RELOC-NEXT: Size: 16
 //RELOC-NEXT: Link: 0
 //RELOC-NEXT: Info: 0
@@ -23,22 +23,19 @@
 //RELOC-NEXT: }
 //RELOC:      Relocations [
 //RELOC-NEXT:   Section (4) .rela.dyn {
-//RELOC-NEXT:     0x120F0 R_X86_64_TPOFF64 tlsshared0 0x0
-//RELOC-NEXT:     0x120F8 R_X86_64_TPOFF64 tlsshared1 0x0
-//RELOC-NEXT:   }
-//RELOC-NEXT:   Section (5) .rela.plt {
-//RELOC-NEXT:     0x13018 R_X86_64_JUMP_SLOT __tls_get_addr 0x0
+//RELOC-NEXT:     0x120B0 R_X86_64_TPOFF64 tlsshared0 0x0
+//RELOC-NEXT:     0x120B8 R_X86_64_TPOFF64 tlsshared1 0x0
 //RELOC-NEXT:   }
 //RELOC-NEXT: ]
 
-//0x11009 + (4304 + 7) = 0x120F0
-//0x11019 + (4296 + 7) = 0x120F8
+//0x11009 + (4256 + 7) = 0x120B0
+//0x11019 + (4248 + 7) = 0x120B8
 // DISASM:      Disassembly of section .text:
 // DISASM-NEXT: _start:
-// DISASM-NEXT: 11000: 64 48 8b 04 25 00 00 00 00 movq %fs:0, %rax
-// DISASM-NEXT: 11009: 48 03 05 e0 10 00 00       addq 4320(%rip), %rax
-// DISASM-NEXT: 11010: 64 48 8b 04 25 00 00 00 00 movq %fs:0, %rax
-// DISASM-NEXT: 11019: 48 03 05 d8 10 00 00       addq 4312(%rip), %rax
+// DISASM-NEXT: 11000: {{.*}} movq %fs:0, %rax
+// DISASM-NEXT: 11009: {{.*}} addq 4256(%rip), %rax
+// DISASM-NEXT: 11010: {{.*}} movq %fs:0, %rax
+// DISASM-NEXT: 11019: {{.*}} addq 4248(%rip), %rax
 
 .section .text
 .globl _start