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

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index caee5da47a0..992b2cfe359 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -58,7 +58,8 @@ void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
                                               const MCSymbol *Lo,
                                               unsigned Size) {
   // If not assigned to the same (valid) fragment, fallback.
-  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment()) {
+  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
+      Hi->isVariable() || Lo->isVariable()) {
     MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
     return;
   }
@@ -155,7 +156,6 @@ void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
   MCStreamer::EmitLabel(Symbol);
 
   getAssembler().registerSymbol(*Symbol);
-  assert(!Symbol->getFragment() && "Unexpected fragment on symbol data!");
 
   // If there is a current fragment, mark the symbol as pointing into it.
   // Otherwise queue the label and set its fragment pointer when we emit the