[MC] Delete unnecessary diagnostic: "No relocation available to represent this relative expression"

Replace

- error: No relocation available to represent this relative expression

with

+ error: symbol 'undef' can not be undefined in a subtraction expression

or

+ error: Cannot represent a difference across sections

Keep !IsPcRel as an assertion after the two diagnostic checks are done.

llvm-svn: 369239

1 files changed, 1 insertions, 15 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 111ba3fab39..97607b43295 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1441,22 +1441,7 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
   MCContext &Ctx = Asm.getContext();
 
   if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
-    // Let A, B and C being the components of Target and R be the location of
-    // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
-    // If it is pcrel, we want to compute (A - B + C - R).
-
-    // In general, ELF has no relocations for -B. It can only represent (A + C)
-    // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
-    // replace B to implement it: (A - R - K + C)
-    if (IsPCRel) {
-      Ctx.reportError(
-          Fixup.getLoc(),
-          "No relocation available to represent this relative expression");
-      return;
-    }
-
     const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
-
     if (SymB.isUndefined()) {
       Ctx.reportError(Fixup.getLoc(),
                       Twine("symbol '") + SymB.getName() +
@@ -1474,6 +1459,7 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
 
     uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
     uint64_t K = SymBOffset - FixupOffset;
+    assert(!IsPCRel && "should have been folded");
     IsPCRel = true;
     C -= K;
   }