[MC, COFF] Add .reloc support for WinCOFF

This adds rudimentary support for a few relocations that we will use for
the CodeView debug format.

llvm-svn: 258216

3 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/MC/MCAsmBackend.cpp b/llvm/lib/MC/MCAsmBackend.cpp
index fcf139b7253..281bba27a0e 100644
--- a/llvm/lib/MC/MCAsmBackend.cpp
+++ b/llvm/lib/MC/MCAsmBackend.cpp
@@ -16,8 +16,8 @@ MCAsmBackend::MCAsmBackend() : HasDataInCodeSupport(false) {}
 
 MCAsmBackend::~MCAsmBackend() {}
 
-bool MCAsmBackend::getFixupKind(StringRef Name, MCFixupKind &MappedKind) const {
-  return false;
+Optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
+  return None;
 }
 
 const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 8ee24786967..19ce9113f27 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -420,13 +420,18 @@ bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name,
   if (!Offset.evaluateAsAbsolute(OffsetValue))
     llvm_unreachable("Offset is not absolute");
 
+  if (OffsetValue < 0)
+    llvm_unreachable("Offset is negative");
+
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
 
-  MCFixupKind Kind;
-  if (!Assembler->getBackend().getFixupKind(Name, Kind))
+  Optional<MCFixupKind> MaybeKind = Assembler->getBackend().getFixupKind(Name);
+  if (!MaybeKind.hasValue())
     return true;
 
+  MCFixupKind Kind = *MaybeKind;
+
   if (Expr == nullptr)
     Expr =
         MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext());
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 646cbb43cae..939b54dd3c8 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -2485,6 +2485,9 @@ bool AsmParser::parseDirectiveReloc(SMLoc DirectiveLoc) {
   if (!Offset->evaluateAsAbsolute(OffsetValue))
     return Error(OffsetLoc, "expression is not a constant value");
 
+  if (OffsetValue < 0)
+    return Error(OffsetLoc, "expression is negative");
+
   if (Lexer.isNot(AsmToken::Comma))
     return TokError("expected comma");
   Lexer.Lex();