Fix --filetype=iasm non-pc-rel fixup offsets (double counted).

src/IceAssembler.cpp

 //===- subzero/src/IceAssembler.cpp - Assembler base class ----------------===//
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 // This is forked from Dart revision 39313.
 // Please update the revision if we merge back changes from Dart.
 // https://code.google.com/p/dart/wiki/GettingTheSource
@@ skipping 114 matching lines @@
   intptr_t CurPosition = 0;
   const intptr_t FixupSize = 4;
   for (const AssemblerFixup *NextFixup : fixups()) {
     intptr_t NextFixupLoc = NextFixup->position();
     for (intptr_t i = CurPosition; i < NextFixupLoc; ++i) {
       Str << "\t.byte 0x";
       Str.write_hex(Buffer.load<uint8_t>(i));
       Str << "\n";
     }
     Str << "\t.long ";
+    // For PCRel fixups, we write the pc-offset from a symbol into the Buffer
+    // (e.g., -4), but we don't represent that in the fixup's offset.
+    // Otherwise the fixup holds the true offset, and so does the Buffer.
+    // Just load the offset from the buffer.
     NextFixup->emit(Ctx, Buffer.load<RelocOffsetT>(NextFixupLoc));
     if (fixupIsPCRel(NextFixup->kind()))
       Str << " - .";
     Str << "\n";
     CurPosition = NextFixupLoc + FixupSize;
     assert(CurPosition <= EndPosition);
   }
   // Handle any bytes that are not prefixed by a fixup.
   for (intptr_t i = CurPosition; i < EndPosition; ++i) {
     Str << "\t.byte 0x";
     Str.write_hex(Buffer.load<uint8_t>(i));
     Str << "\n";
   }
 }
 
 } // end of namespace Ice