[ELF2] R_X86_64_64 plt relocation implemented.

[grimar]

Summary

This little patch is a final point in fix for https://llvm.org/bugs/show_bug.cgi?id=25175.

It`s make sample from issue description to work with -O0 optimization flag (with -O0 it generates R_X86_64_64 plt relocation).
Previous patch that implemented copy relocations (http://reviews.llvm.org/D14090) fixed -O1,2,3 cases.

[ruiu]

LGTM with a nit.

ELF/Target.cpp

265–274 ↗

(On Diff #38672)

This function is called only when relocNeedsPlt returns true, so

if (Type == R_X86_64_PLT32)
  return R_X86_64_PC32;
return Type;

lld/trunk/ELF/Target.cpp

bool X86_64TargetInfo::relocNeedsCopy(uint32_t Type,
   return false;
 }
 
 bool X86_64TargetInfo::relocNeedsGot(uint32_t Type, const SymbolBody &S) const {
   return Type == R_X86_64_GOTPCREL || relocNeedsPlt(Type, S);
 }
 
 unsigned X86_64TargetInfo::getPLTRefReloc(unsigned Type) const {
-  switch (Type) {
-  case R_X86_64_32:
-    return R_X86_64_32;
-  case R_X86_64_PC32:
-  case R_X86_64_PLT32:
+  if (Type == R_X86_64_PLT32)
     return R_X86_64_PC32;
-  }
-  llvm_unreachable("Unexpected relocation");
+  return Type;
 }
 
 bool X86_64TargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
   if (relocNeedsCopy(Type, S))
     return false;
 
   switch (Type) {
   default:
     return false;
   case R_X86_64_32:
+  case R_X86_64_64:
   case R_X86_64_PC32:
     // This relocation is defined to have a value of (S + A - P).
     // The problems start when a non PIC program calls a function in a shared
     // library.
     // In an ideal world, we could just report an error saying the relocation
     // can overflow at runtime.
     // In the real world with glibc, crt1.o has a R_X86_64_PC32 pointing to
     // libc.so.

lld/trunk/test/elf2/dynamic-reloc-index.s

 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t2.o
 // RUN: ld.lld2 -shared %t2.o -o %t2.so
 // RUN: ld.lld2 %t.o %t2.so -o %t
 // RUN: llvm-readobj -r %t | FileCheck %s
 
 // We used to record the wrong symbol index for this test
 
 // CHECK:      Relocations [
-// CHECK-NEXT:   Section ({{.*}}) .rela.dyn {
-// CHECK-NEXT:     0x11000 R_X86_64_64 bar 0x0
+// CHECK-NEXT:   Section ({{.*}}) .rela.plt {
+// CHECK-NEXT:     0x120C8 R_X86_64_JUMP_SLOT bar 0x0
 // CHECK-NEXT:   }
 // CHECK-NEXT: ]
 
         .global foobar
 foobar:
         .global zedx
 zedx:
         .global _start
 _start:
 .quad bar

lld/trunk/test/elf2/dynamic-reloc.s

 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 // 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/dynamic-reloc.s -o %t3.o
 // RUN: ld.lld2 -shared %t2.o -o %t2.so
 // RUN: ld.lld2 %t.o %t3.o %t2.so -o %t
 // RUN: llvm-readobj -dynamic-table -r --expand-relocs -s %t | FileCheck %s
 // REQUIRES: x86
 
 // CHECK:      Index: 1
 // CHECK-NEXT: Name: .dynsym
 
-// CHECK:      Name: .rela.dyn
+// CHECK:      Name: .rela.plt
 // CHECK-NEXT: Type: SHT_RELA
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT: ]
 // CHECK-NEXT: Address: [[RELAADDR:.*]]
 // CHECK-NEXT: Offset:
 // CHECK-NEXT: Size: [[RELASIZE:.*]]
 // CHECK-NEXT: Link: 1
 // CHECK-NEXT: Info: 0
 // CHECK-NEXT: AddressAlignment: 8
 // CHECK-NEXT: EntrySize: 24
 
 // CHECK:      Name: .text
 // CHECK-NEXT: Type: SHT_PROGBITS
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT:   SHF_EXECINSTR
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: [[ADDR:.*]]
+// CHECK-NEXT: Address: 0x11000
 
 // CHECK:      Relocations [
-// CHECK-NEXT:   Section ({{.*}}) .rela.dyn {
+// CHECK-NEXT:   Section ({{.*}}) .rela.plt {
 // CHECK-NEXT:     Relocation {
-// CHECK-NEXT:       Offset: [[ADDR]]
-// CHECK-NEXT:       Type: R_X86_64_64
+// CHECK-NEXT:       Offset: 0x120C8
+// CHECK-NEXT:       Type: R_X86_64_JUMP_SLOT
 // CHECK-NEXT:       Symbol: bar
-// CHECK-NEXT:       Addend: 0x42
+// CHECK-NEXT:       Addend: 0x0
 // CHECK-NEXT:     }
 // CHECK-NEXT:   }
 // CHECK-NEXT: ]
 
 // CHECK: DynamicSection [
 // CHECK-NEXT:  Tag                Type                 Name/Value
-// CHECK-NEXT:  0x0000000000000007 RELA                 [[RELAADDR]]
-// CHECK-NEXT:  0x0000000000000008 RELASZ               [[RELASIZE]] (bytes)
-// CHECK-NEXT:  0x0000000000000009 RELAENT              24 (bytes)
+// CHECK-NEXT:  0x0000000000000017 JMPREL               0x10200
+// CHECK-NEXT:  0x0000000000000002 PLTRELSZ             24 (bytes)
+// CHECK-NEXT:  0x0000000000000003 PLTGOT               0x120B0
+// CHECK-NEXT:  0x0000000000000014 PLTREL               RELA
 // CHECK-NEXT:  0x0000000000000006 SYMTAB
 // CHECK-NEXT:  0x000000000000000B SYMENT               24 (bytes)
 // CHECK-NEXT:  0x0000000000000005 STRTAB
 // CHECK-NEXT:  0x000000000000000A STRSZ
 // CHECK-NEXT:  0x0000000000000004 HASH
 // CHECK-NEXT:  0x0000000000000001 NEEDED               SharedLibrary ({{.*}}2.so)
 // CHECK-NEXT:  0x0000000000000000 NULL                 0x0
 // CHECK-NEXT: ]
 
-
 .global _start
 _start:
 .quad bar + 0x42
 .weak foo
 .quad foo
 call main