[ELF][PPC] Support initial relocation type R_PPC64_UADDR64

[MaskRay]

Depends on D66072

ELF/Arch/PPC64.cpp

default:
     llvm_unreachable("unknown relocation for IE to LE");
     break;
   }
 }
 
 RelExpr PPC64::getRelExpr(RelType type, const Symbol &s,
                           const uint8_t *loc) const {
   switch (type) {
+  case R_PPC64_UADDR64:
+    return R_ABS;
   case R_PPC64_GOT16:
   case R_PPC64_GOT16_DS:
   case R_PPC64_GOT16_HA:
   case R_PPC64_GOT16_HI:
   case R_PPC64_GOT16_LO:
   case R_PPC64_GOT16_LO_DS:
     return R_GOT_OFF;
   case R_PPC64_TOC16:
RelExpr PPC64::getRelExpr(RelType type, const Symbol &s,
   default:
     return R_ABS;
   }
 }
 
 RelType PPC64::getDynRel(RelType type) const {
   if (type == R_PPC64_ADDR64 || type == R_PPC64_TOC)
     return R_PPC64_ADDR64;
+  if (type == R_PPC64_UADDR64)
+    return type;
   return R_PPC64_NONE;
 }
 
 void PPC64::writeGotHeader(uint8_t *buf) const {
   write64(buf, getPPC64TocBase());
 }
 
 void PPC64::writePltHeader(uint8_t *buf) const {
case R_PPC64_TPREL16:
     checkInt(loc, val, 16, originalType);
     write16(loc, val);
     break;
   case R_PPC64_REL32:
     checkInt(loc, val, 32, type);
     write32(loc, val);
     break;
   case R_PPC64_ADDR64:
+  case R_PPC64_UADDR64:
   case R_PPC64_REL64:
   case R_PPC64_TOC:
     write64(loc, val);
     break;
   case R_PPC64_REL14: {
     uint32_t mask = 0x0000FFFC;
     checkInt(loc, val, 16, type);
     checkAlignment(loc, val, 4, type);

test/ELF/ppc64-reloc-uaddr.s

+# REQUIRES: ppc
+# RUN: llvm-mc -filetype=obj -triple=powerpc64le-unknown-linux %s -o %t.o
+# RUN: ld.lld -pie %t.o --defsym=external=42 -o %t
+# RUN: llvm-readobj -r -x .data %t | FileCheck --check-prefix=PIE %s
+# RUN: ld.lld -shared %t.o -o %t.so
+# RUN: llvm-readobj -r %t.so | FileCheck --check-prefix=SHARED %s
+
+## 'local' and 'global' are non-preemptable, but we have to use R_PPC64_UADDR64,
+## instead of misaligned R_PPC64_RELATIVE.
+# PIE:      .rela.dyn {
+# PIE-NEXT:   0x20001 R_PPC64_UADDR64 - 0x1
+# PIE-NEXT:   0x20011 R_PPC64_UADDR64 - 0x3
+# PIE-NEXT: }
+
+## 'external' is absolute of value 42. The field is filled at link time.
+# PIE:      section '.data':
+# PIE-NEXT: 0x00020000 00000000 00000000 002c0000 00000000
+# PIE-NEXT: 0x00020010 00000000 00000000 00
+
+## 'local' is non-preemptable, but we have to use R_PPC64_UADDR64.
+## Preemptable 'external' and 'global' are associated with symbols.
+# SHARED:      .rela.dyn {
+# SHARED-NEXT:   0x20001 R_PPC64_UADDR64 - 0x1
+# SHARED-NEXT:   0x20009 R_PPC64_UADDR64 external 0x2
+# SHARED-NEXT:   0x20011 R_PPC64_UADDR64 global 0x3
+# SHARED-NEXT: }
+
+.data
+.globl global
+global:
+local:
+
+.byte 0
+.quad local + 1
+.quad external + 2
+.quad global + 3