[llvm-mc] - Produce R_X86_64_PLT32 for "call/jmp foo".

For instructions like call foo and jmp foo patch changes
relocation produced from R_X86_64_PC32 to R_X86_64_PLT32.
Relocation can be used as a marker for 32-bit PC-relative branches.
Linker will reduce PLT32 relocation to PC32 if function is defined locally.

Differential revision: https://reviews.llvm.org/D43383

llvm-svn: 325569

6 files changed, 39 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index da4ca665d83..eea94b2eb1d 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
@@ -46,6 +46,7 @@ static unsigned getFixupKindLog2Size(unsigned Kind) {
   case X86::reloc_signed_4byte:
   case X86::reloc_signed_4byte_relax:
   case X86::reloc_global_offset_table:
+  case X86::reloc_branch_4byte_pcrel:
   case FK_SecRel_4:
   case FK_Data_4:
     return 2;
@@ -86,6 +87,7 @@ public:
         {"reloc_signed_4byte_relax", 0, 32, 0},
         {"reloc_global_offset_table", 0, 32, 0},
         {"reloc_global_offset_table8", 0, 64, 0},
+        {"reloc_branch_4byte_pcrel", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
     };
 
     if (Kind < FirstTargetFixupKind)
@@ -93,6 +95,7 @@ public:
 
     assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
            "Invalid kind!");
+    assert(Infos[Kind - FirstTargetFixupKind].Name && "Empty fixup name!");
     return Infos[Kind - FirstTargetFixupKind];
   }
 
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
index 4cdbae4d0d9..2ecbb80cd06 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -75,6 +75,9 @@ static X86_64RelType getType64(unsigned Kind,
   case X86::reloc_riprel_4byte_relax_rex:
   case X86::reloc_riprel_4byte_movq_load:
     return RT64_32;
+  case X86::reloc_branch_4byte_pcrel:
+    Modifier = MCSymbolRefExpr::VK_PLT;
+    return RT64_32;
   case FK_PCRel_2:
   case FK_Data_2:
     return RT64_16;
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86FixupKinds.h b/llvm/lib/Target/X86/MCTargetDesc/X86FixupKinds.h
index dfdc9ec29ae..3c04b13e002 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86FixupKinds.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86FixupKinds.h
@@ -30,6 +30,7 @@ enum Fixups {
                                              // of the instruction. Used only
                                              // for _GLOBAL_OFFSET_TABLE_.
   reloc_global_offset_table8,                // 64-bit variant.
+  reloc_branch_4byte_pcrel,                  // 32-bit PC relative branch.
   // Marker
   LastTargetFixupKind,
   NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index 4ddc1f0ba42..608dc4acb04 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -152,6 +152,8 @@ public:
 
   uint8_t DetermineREXPrefix(const MCInst &MI, uint64_t TSFlags,
                              int MemOperand, const MCInstrDesc &Desc) const;
+
+  bool isPCRel32Branch(const MCInst &MI) const;
 };
 
 } // end anonymous namespace
@@ -276,6 +278,22 @@ static bool HasSecRelSymbolRef(const MCExpr *Expr) {
   return false;
 }
 
+bool X86MCCodeEmitter::isPCRel32Branch(const MCInst &MI) const {
+  unsigned Opcode = MI.getOpcode();
+  const MCInstrDesc &Desc = MCII.get(Opcode);
+  if ((Opcode != X86::CALL64pcrel32 && Opcode != X86::JMP_4) ||
+      getImmFixupKind(Desc.TSFlags) != FK_PCRel_4)
+    return false;
+
+  unsigned CurOp = X86II::getOperandBias(Desc);
+  const MCOperand &Op = MI.getOperand(CurOp);
+  if (!Op.isExpr())
+    return false;
+
+  const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Op.getExpr());
+  return Ref && Ref->getKind() == MCSymbolRefExpr::VK_None;
+}
+
 void X86MCCodeEmitter::
 EmitImmediate(const MCOperand &DispOp, SMLoc Loc, unsigned Size,
               MCFixupKind FixupKind, unsigned &CurByte, raw_ostream &OS,
@@ -331,7 +349,8 @@ EmitImmediate(const MCOperand &DispOp, SMLoc Loc, unsigned Size,
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte) ||
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte_movq_load) ||
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax) ||
-      FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax_rex))
+      FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax_rex) ||
+      FixupKind == MCFixupKind(X86::reloc_branch_4byte_pcrel))
     ImmOffset -= 4;
   if (FixupKind == FK_PCRel_2)
     ImmOffset -= 2;
@@ -1287,9 +1306,18 @@ encodeInstruction(const MCInst &MI, raw_ostream &OS,
     EmitByte(BaseOpcode, CurByte, OS);
     break;
   }
-  case X86II::RawFrm:
+  case X86II::RawFrm: {
     EmitByte(BaseOpcode, CurByte, OS);
+
+    if (!is64BitMode(STI) || !isPCRel32Branch(MI))
+      break;
+
+    const MCOperand &Op = MI.getOperand(CurOp++);
+    EmitImmediate(Op, MI.getLoc(), X86II::getSizeOfImm(TSFlags),
+                  MCFixupKind(X86::reloc_branch_4byte_pcrel), CurByte, OS,
+                  Fixups);
     break;
+  }
   case X86II::RawFrmMemOffs:
     // Emit segment override opcode prefix as needed.
     EmitSegmentOverridePrefix(CurByte, 1, MI, OS);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index 965f7de809b..22773e64409 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -94,6 +94,7 @@ static unsigned getFixupKindLog2Size(unsigned Kind) {
   case X86::reloc_riprel_4byte_movq_load:
   case X86::reloc_signed_4byte:
   case X86::reloc_signed_4byte_relax:
+  case X86::reloc_branch_4byte_pcrel:
   case FK_Data_4: return 2;
   case FK_Data_8: return 3;
   }
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
index 5139bb46b56..291056e3526 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
@@ -62,6 +62,7 @@ unsigned X86WinCOFFObjectWriter::getRelocType(MCContext &Ctx,
     case X86::reloc_riprel_4byte_movq_load:
     case X86::reloc_riprel_4byte_relax:
     case X86::reloc_riprel_4byte_relax_rex:
+    case X86::reloc_branch_4byte_pcrel:
       return COFF::IMAGE_REL_AMD64_REL32;
     case FK_Data_4:
     case X86::reloc_signed_4byte: