commit e3a20f57d927e422874a8e7730bb7590515b586d
author Rafael Espindola <rafael.espindola@gmail.com> Mon Oct 05 12:07:05 2015 +0000
committer Rafael Espindola <rafael.espindola@gmail.com> Mon Oct 05 12:07:05 2015 +0000
tree c173b7c07c1267489d17715ee156ee7a8412a78c
parent ee4e08ba94e2ee04ad7ad0e0e396147be417c79f

Fix pr24486.

This extends the work done in r233995 so that now getFragment (in addition to
getSection) also works for variable symbols.

With that the existing logic to decide if a-b can be computed works even if
a or b are variables. Given that, the expression evaluation can avoid expanding
variables as aggressively and that in turn lets the relocation code see the
original variable.

In order for this to work with the asm streamer, there is now a dummy fragment
per section. It is used to assign a section to a symbol when no other fragment
exists.

This patch is a joint work by Maxim Ostapenko andy myself.

llvm-svn: 249303

llvm/lib/MC/MCAssembler.cpp

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index d93bf44..143d284 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -277,7 +277,7 @@
     : Kind(Kind), HasInstructions(HasInstructions), AlignToBundleEnd(false),
       BundlePadding(BundlePadding), Parent(Parent), Atom(nullptr),
       Offset(~UINT64_C(0)) {
-  if (Parent)
+  if (Parent && !isDummy())
     Parent->getFragmentList().push_back(this);
 }
 
@@ -319,6 +319,9 @@
     case FT_SafeSEH:
       delete cast<MCSafeSEHFragment>(this);
       return;
+    case FT_Dummy:
+      delete cast<MCDummyFragment>(this);
+      return;
   }
 }
 
@@ -411,7 +414,7 @@
     return &S;
 
   // Absolute and undefined symbols have no defining atom.
-  if (!S.getFragment())
+  if (!S.isInSection())
     return nullptr;
 
   // Non-linker visible symbols in sections which can't be atomized have no
@@ -547,6 +550,8 @@
     return cast<MCDwarfLineAddrFragment>(F).getContents().size();
   case MCFragment::FT_DwarfFrame:
     return cast<MCDwarfCallFrameFragment>(F).getContents().size();
+  case MCFragment::FT_Dummy:
+    llvm_unreachable("Should not have been added");
   }
 
   llvm_unreachable("invalid fragment kind");
@@ -780,6 +785,8 @@
     OW->writeBytes(CF.getContents());
     break;
   }
+  case MCFragment::FT_Dummy:
+    llvm_unreachable("Should not have been added");
   }
 
   assert(OW->getStream().tell() - Start == FragmentSize &&
@@ -1147,6 +1154,9 @@
   case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
   case MCFragment::FT_SafeSEH:    OS << "MCSafeSEHFragment"; break;
+  case MCFragment::FT_Dummy:
+    OS << "MCDummyFragment";
+    break;
   }
 
   OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
@@ -1245,6 +1255,8 @@
     OS << " Sym:" << F->getSymbol();
     break;
   }
+  case MCFragment::FT_Dummy:
+    break;
   }
   OS << ">";
 }