[AArch64] Implement R_AARCH64_ LD_PREL_LO19.

Fixes PR34660.

Differential Revision:  https://reviews.llvm.org/D38053

llvm-svn: 313841

4 files changed, 32 insertions, 0 deletions

diff --git a/lld/ELF/Arch/AArch64.cpp b/lld/ELF/Arch/AArch64.cpp
index 8fa79c092d2..7493b6c5e83 100644
--- a/lld/ELF/Arch/AArch64.cpp
+++ b/lld/ELF/Arch/AArch64.cpp
@@ -92,6 +92,7 @@ RelExpr AArch64::getRelExpr(uint32_t Type, const SymbolBody &S,
   case R_AARCH64_PREL32:
   case R_AARCH64_PREL64:
   case R_AARCH64_ADR_PREL_LO21:
+  case R_AARCH64_LD_PREL_LO19:
     return R_PC;
   case R_AARCH64_ADR_PREL_PG_HI21:
     return R_PAGE_PC;
@@ -247,6 +248,7 @@ void AArch64::relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
     or32le(Loc, (Val & 0x0FFFFFFC) >> 2);
     break;
   case R_AARCH64_CONDBR19:
+  case R_AARCH64_LD_PREL_LO19:
     checkInt<21>(Loc, Val, Type);
     or32le(Loc, (Val & 0x1FFFFC) << 3);
     break;
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 016234abc90..338efcbea28 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -487,6 +487,7 @@ static uint64_t getAArch64UndefinedRelativeWeakVA(uint64_t Type, uint64_t A,
   case R_AARCH64_PREL32:
   case R_AARCH64_PREL64:
   case R_AARCH64_ADR_PREL_LO21:
+  case R_AARCH64_LD_PREL_LO19:
     return P + A;
   }
   llvm_unreachable("AArch64 pc-relative relocation expected\n");
diff --git a/lld/test/ELF/aarch64-undefined-weak.s b/lld/test/ELF/aarch64-undefined-weak.s
index 1c21213643a..c0f6ffe99aa 100644
--- a/lld/test/ELF/aarch64-undefined-weak.s
+++ b/lld/test/ELF/aarch64-undefined-weak.s
@@ -30,6 +30,8 @@ _start:
  .xword target - .
 // R_AARCH64_PREL16
  .hword target - .
+// R_AARCH64_LD_PREL_LO19
+ ldr x8, target
 
 // CHECK: Disassembly of section .text:
 // 131076 = 0x20004
@@ -43,3 +45,5 @@ _start:
 // CHECK-NEXT:    2001c: {{.*}} .word   0x00000000
 // CHECK-NEXT:    20020: {{.*}} .word   0x00000000
 // CHECK-NEXT:    20024: {{.*}} .short  0x0000
+// CHECK:         $x.2:
+// CHECK-NEXT:    20026: {{.*}} ldr     x8, #0
diff --git a/lld/test/ELF/pr34660.s b/lld/test/ELF/pr34660.s
new file mode 100644
index 00000000000..11191169659
--- /dev/null
+++ b/lld/test/ELF/pr34660.s
@@ -0,0 +1,25 @@
+# REQUIRES: aarch64
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-linux-none %s -o %t.o
+# RUN: ld.lld -shared %t.o -o %t
+# RUN: llvm-objdump %t -d | FileCheck %s --check-prefix=DISASM
+# RUN: llvm-readobj -elf-output-style=GNU %t -t | FileCheck %s --check-prefix=SYM
+
+# It would be much easier to understand/read this test if llvm-objdump would print
+# the immediates in hex.
+# IMM = hex(65540) = 0x10004
+# PC = 0x10000
+# As the relocation is PC-relative, IMM + PC = 0x20004 which is the VA of the
+# correct symbol.
+
+# DISASM: Disassembly of section .text:
+# DISASM-NEXT: $x.0:
+# DISASM-NEXT:   10000:       28 00 08 58     ldr     x8, #65540
+
+# SYM: Symbol table '.symtab'
+# SYM:  0000000000020004     0 NOTYPE  LOCAL  DEFAULT    5 patatino
+
+  ldr x8, patatino
+  .data
+  .zero 4
+patatino: