[SystemZ] Add support for .reloc assembler directive

Add support for the .reloc directive along the lines of
other back-ends.

This fixes a regression after https://reviews.llvm.org/D104080
was merged, since that patch presupposed support for .reloc.

lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp

@@ -8,6 +8,7 @@
 
 #include "MCTargetDesc/SystemZMCFixups.h"
 #include "MCTargetDesc/SystemZMCTargetDesc.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCFixupKindInfo.h"
@@ -49,7 +50,10 @@ public:
   unsigned getNumFixupKinds() const override {
     return SystemZ::NumTargetFixupKinds;
   }
+  Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
+  bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
+                             const MCValue &Target) override;
   void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
                   const MCValue &Target, MutableArrayRef<char> Data,
                   uint64_t Value, bool IsResolved,
@@ -67,6 +71,22 @@ public:
 };
 } // end anonymous namespace
 
+Optional<MCFixupKind> SystemZMCAsmBackend::getFixupKind(StringRef Name) const {
+  unsigned Type = llvm::StringSwitch<unsigned>(Name)
+#define ELF_RELOC(X, Y) .Case(#X, Y)
+#include "llvm/BinaryFormat/ELFRelocs/SystemZ.def"
+#undef ELF_RELOC
+			.Case("BFD_RELOC_NONE", ELF::R_390_NONE)
+			.Case("BFD_RELOC_8", ELF::R_390_8)
+			.Case("BFD_RELOC_16", ELF::R_390_16)
+			.Case("BFD_RELOC_32", ELF::R_390_32)
+			.Case("BFD_RELOC_64", ELF::R_390_64)
+			.Default(-1u);
+  if (Type != -1u)
+    return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
+  return None;
+}
+
 const MCFixupKindInfo &
 SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
   const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
@@ -77,6 +97,11 @@ SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
     { "FK_390_TLS_CALL", 0, 0, 0 }
   };
 
+  // Fixup kinds from .reloc directive are like R_390_NONE. They
+  // do not require any extra processing.
+  if (Kind >= FirstLiteralRelocationKind)
+    return MCAsmBackend::getFixupKindInfo(FK_NONE);
+
   if (Kind < FirstTargetFixupKind)
     return MCAsmBackend::getFixupKindInfo(Kind);
 
@@ -85,6 +110,12 @@ SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
   return Infos[Kind - FirstTargetFixupKind];
 }
 
+bool SystemZMCAsmBackend::shouldForceRelocation(const MCAssembler &,
+						const MCFixup &Fixup,
+						const MCValue &) {
+  return Fixup.getKind() >= FirstLiteralRelocationKind;
+}
+
 void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
                                      const MCFixup &Fixup,
                                      const MCValue &Target,
@@ -92,6 +123,8 @@ void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
                                      bool IsResolved,
                                      const MCSubtargetInfo *STI) const {
   MCFixupKind Kind = Fixup.getKind();
+  if (Kind >= FirstLiteralRelocationKind)
+    return;
   unsigned Offset = Fixup.getOffset();
   unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
   unsigned Size = (BitSize + 7) / 8;

lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp

@@ -117,8 +117,10 @@ unsigned SystemZObjectWriter::getRelocType(MCContext &Ctx,
                                            const MCValue &Target,
                                            const MCFixup &Fixup,
                                            bool IsPCRel) const {
-  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
   unsigned Kind = Fixup.getKind();
+  if (Kind >= FirstLiteralRelocationKind)
+    return Kind - FirstLiteralRelocationKind;
+  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
   switch (Modifier) {
   case MCSymbolRefExpr::VK_None:
     if (IsPCRel)

test/MC/SystemZ/reloc-directive.s

@@ -0,0 +1,51 @@
+# RUN: llvm-mc -triple=s390x-linux-gnu %s | FileCheck --check-prefix=PRINT %s
+
+# RUN: llvm-mc -filetype=obj -triple=s390x-linux-gnu %s -o %t
+# RUN: llvm-readobj -r %t | FileCheck %s
+
+# PRINT:      .reloc 2, R_390_NONE, .data
+# PRINT-NEXT: .reloc 1, R_390_NONE, foo+4
+# PRINT-NEXT: .reloc 0, R_390_NONE, 8
+# PRINT-NEXT: .reloc 0, R_390_64, .data+2
+# PRINT-NEXT: .reloc 0, R_390_GOTENT, foo+3
+# PRINT-NEXT: .reloc 0, R_390_PC32DBL, 6
+# PRINT:      .reloc 0, BFD_RELOC_NONE, 9
+# PRINT-NEXT: .reloc 0, BFD_RELOC_8, 9
+# PRINT-NEXT: .reloc 0, BFD_RELOC_16, 9
+# PRINT-NEXT: .reloc 0, BFD_RELOC_32, 9
+# PRINT-NEXT: .reloc 0, BFD_RELOC_64, 9
+
+# CHECK:      0x2 R_390_NONE .data 0x0
+# CHECK-NEXT: 0x1 R_390_NONE foo 0x4
+# CHECK-NEXT: 0x0 R_390_NONE - 0x8
+# CHECK-NEXT: 0x0 R_390_64 .data 0x2
+# CHECK-NEXT: 0x0 R_390_GOTENT foo 0x3
+# CHECK-NEXT: 0x0 R_390_PC32DBL - 0x6
+# CHECK-NEXT: 0x0 R_390_NONE - 0x9
+# CHECK-NEXT: 0x0 R_390_8 - 0x9
+# CHECK-NEXT: 0x0 R_390_16 - 0x9
+# CHECK-NEXT: 0x0 R_390_32 - 0x9
+# CHECK-NEXT: 0x0 R_390_64 - 0x9
+
+.text
+  br %r14
+  nop
+  nop
+  .reloc 2, R_390_NONE, .data
+  .reloc 1, R_390_NONE, foo+4
+  .reloc 0, R_390_NONE, 8
+  .reloc 0, R_390_64, .data+2
+  .reloc 0, R_390_GOTENT, foo+3
+  .reloc 0, R_390_PC32DBL, 6
+
+  .reloc 0, BFD_RELOC_NONE, 9
+  .reloc 0, BFD_RELOC_8, 9
+  .reloc 0, BFD_RELOC_16, 9
+  .reloc 0, BFD_RELOC_32, 9
+  .reloc 0, BFD_RELOC_64, 9
+
+.data
+.globl foo
+foo:
+  .word 0
+  .word 0