ARM: add support for segment base relocations (SBREL)

This adds support for parsing and emitting the SBREL relocation variant for the
ARM target.  Handling this relocation variant is necessary for supporting the
full ARM ELF specification.  Addresses PR22128.

llvm-svn: 225595

2 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index c7739b4d792..a821a6b0b53 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -200,6 +200,9 @@ unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
       case MCSymbolRefExpr::VK_ARM_PREL31:
         Type = ELF::R_ARM_PREL31;
         break;
+      case MCSymbolRefExpr::VK_ARM_SBREL:
+        Type = ELF::R_ARM_SBREL32;
+        break;
       case MCSymbolRefExpr::VK_ARM_TLSLDO:
         Type = ELF::R_ARM_TLS_LDO32;
         break;
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
index f9403063dd6..99b5c628f50 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -553,6 +553,10 @@ public:
   /// necessary.
   void EmitValueImpl(const MCExpr *Value, unsigned Size,
                      const SMLoc &Loc) override {
+    if (const MCSymbolRefExpr *SRE = dyn_cast_or_null<MCSymbolRefExpr>(Value))
+      if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_SBREL && !(Size == 4))
+        getContext().FatalError(Loc, "relocated expression must be 32-bit");
+
     EmitDataMappingSymbol();
     MCELFStreamer::EmitValueImpl(Value, Size);
   }