[ELF2] Implement PPC64TargetInfo::isRelRelative

[hfinkel]

Summary

This is essentially patern-matching against the x86 target. It is still missing a test case, but feedback is certainly appreciated.

[ruiu]

This change seems good, but we need a test for this indeed.

[davide]

Hal, I think the change is correct. Please add a test preferably written in assembler.
The only comment if have is -- can you please add \n immediately right before and after the function?

[hfinkel]

Added a test case (and some new lines).

[ruiu]

LGTM

[hfinkel]

r250102, thanks!

ELF/Target.h

 public:
   PPC64TargetInfo();
   void writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                      uint64_t PltEntryAddr) const override;
   bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
   bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
   void relocateOne(uint8_t *Buf, const void *RelP, uint32_t Type,
                    uint64_t BaseAddr, uint64_t SymVA) const override;
+  bool isRelRelative(uint32_t Type) const override;
 };
 
 class PPCTargetInfo final : public TargetInfo {
 public:
   PPCTargetInfo();
   void writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                      uint64_t PltEntryAddr) const override;
   bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;

ELF/Target.cpp

 static uint16_t applyPPCHighesta(uint64_t V) {
   return ((V + 0x8000) >> 48) & 0xffff;
 }
 
 PPC64TargetInfo::PPC64TargetInfo() {
   PCRelReloc = R_PPC64_REL24;
   GotReloc = R_PPC64_GLOB_DAT;
   GotRefReloc = R_PPC64_REL64;
+  RelativeReloc = R_PPC64_RELATIVE;
   PltEntrySize = 32;
   PageSize = 65536;
   VAStart = 0x10000000;
 }
 
 static uint64_t getPPC64TocBase() {
   // The TOC consists of sections .got, .toc, .tocbss, .plt in that
   // order. The TOC starts where the first of these sections starts.

 bool PPC64TargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
   if (Type != R_PPC64_REL24)
     return false;
 
   // These are function calls that need to be redirected through a PLT stub.
   return S.isShared() || (S.isUndefined() && S.isWeak());
 }
 
+bool PPC64TargetInfo::isRelRelative(uint32_t Type) const {
+  switch (Type) {
+  default:
+    return false;
+  case R_PPC64_REL24:
+  case R_PPC64_REL14:
+  case R_PPC64_REL14_BRTAKEN:
+  case R_PPC64_REL14_BRNTAKEN:
+  case R_PPC64_REL32:
+    return true;
+  }
+}
+
 void PPC64TargetInfo::relocateOne(uint8_t *Buf, const void *RelP, uint32_t Type,
                                   uint64_t BaseAddr, uint64_t SymVA) const {
   typedef ELFFile<ELF64BE>::Elf_Rela Elf_Rela;
   auto &Rel = *reinterpret_cast<const Elf_Rela *>(RelP);
 
   uint8_t *L = Buf + Rel.r_offset;
   uint64_t S = SymVA;
   int64_t A = Rel.r_addend;

test/elf2/relative-dynamic-reloc-ppc64.s

+// RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
+// RUN: ld.lld2 -shared %t.o -o %t.so
+// RUN: llvm-readobj -t -r -dyn-symbols %t.so | FileCheck %s
+
+// Test that we create R_PPC64_RELATIVE relocations but don't put any
+// symbols in the dynamic symbol table.
+
+// CHECK:      Relocations [
+// CHECK-NEXT:   Section ({{.*}}) .rela.dyn {
+// CHECK-NEXT:     0x[[FOO_ADDR:.*]] R_PPC64_RELATIVE - 0x[[FOO_ADDR]]
+// CHECK-NEXT:     0x[[BAR_ADDR:.*]] R_PPC64_RELATIVE - 0x[[BAR_ADDR]]
+// CHECK-NEXT:     0x20010 R_PPC64_RELATIVE - 0x20009
+// CHECK-NEXT:     0x{{.*}} R_PPC64_RELATIVE - 0x[[ZED_ADDR:.*]]
+// CHECK-NEXT:     0x{{.*}} R_PPC64_RELATIVE - 0x[[FOO_ADDR]]
+// CHECK-NEXT:     0x10008 R_PPC64_ADDR64 external 0x0
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+
+// CHECK:      Symbols [
+// CHECK:        Name: foo
+// CHECK-NEXT:   Value: 0x[[FOO_ADDR]]
+// CHECK:        Name: bar
+// CHECK-NEXT:   Value: 0x[[BAR_ADDR]]
+// CHECK:        Name: zed
+// CHECK-NEXT:   Value: 0x[[ZED_ADDR]]
+// CHECK:      ]
+
+// CHECK:      DynamicSymbols [
+// CHECK-NEXT:   Symbol {
+// CHECK-NEXT:     Name: @ (0)
+// CHECK-NEXT:     Value: 0x0
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Binding: Local
+// CHECK-NEXT:     Type: None
+// CHECK-NEXT:     Other: 0
+// CHECK-NEXT:     Section: Undefined
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Symbol {
+// CHECK-NEXT:     Name: external@
+// CHECK-NEXT:     Value: 0x0
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Binding: Global
+// CHECK-NEXT:     Type: None
+// CHECK-NEXT:     Other: 0
+// CHECK-NEXT:     Section: Undefined
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+
+foo:
+        .quad foo
+
+        .hidden bar
+        .global bar
+bar:
+        .quad bar
+        .quad bar + 1
+
+        .hidden zed
+        .comm zed,1
+        .quad zed
+
+        .section abc,"a"
+        .quad foo
+
+        .quad external