[MC] Support labels as offsets in .reloc directive

Currently, expressions like

  .reloc 1f, R_MIPS_JALR, foo
  1: nop

are not allowed, ie. an offset in .reloc can only be absolute value.
This patch adds support for labels as offsets.
If offset is a forward declared label, MCObjectStreamer keeps the fixup locally
and adds it to the fixups vector after the label (and its offset) is defined.
label+number is not supported yet.

Differential revision: https://reviews.llvm.org/D53990

llvm-svn: 347397

1 files changed, 9 insertions, 9 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 7299ed29e4b..aa07eee4491 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -2938,20 +2938,20 @@ bool AsmParser::parseDirectiveAscii(StringRef IDVal, bool ZeroTerminated) {
 bool AsmParser::parseDirectiveReloc(SMLoc DirectiveLoc) {
   const MCExpr *Offset;
   const MCExpr *Expr = nullptr;
-
-  SMLoc OffsetLoc = Lexer.getTok().getLoc();
   int64_t OffsetValue;
-  // We can only deal with constant expressions at the moment.
+  SMLoc OffsetLoc = Lexer.getTok().getLoc();
 
   if (parseExpression(Offset))
     return true;
 
-  if (check(!Offset->evaluateAsAbsolute(OffsetValue,
-                                        getStreamer().getAssemblerPtr()),
-            OffsetLoc, "expression is not a constant value") ||
-      check(OffsetValue < 0, OffsetLoc, "expression is negative") ||
-      parseToken(AsmToken::Comma, "expected comma") ||
-      check(getTok().isNot(AsmToken::Identifier), "expected relocation name"))
+  if ((Offset->evaluateAsAbsolute(OffsetValue,
+                                  getStreamer().getAssemblerPtr()) &&
+       check(OffsetValue < 0, OffsetLoc, "expression is negative")) ||
+      (check(Offset->getKind() != llvm::MCExpr::Constant &&
+             Offset->getKind() != llvm::MCExpr::SymbolRef,
+             OffsetLoc, "expected non-negative number or a label")) ||
+      (parseToken(AsmToken::Comma, "expected comma") ||
+       check(getTok().isNot(AsmToken::Identifier), "expected relocation name")))
     return true;
 
   SMLoc NameLoc = Lexer.getTok().getLoc();