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, 5 insertions, 4 deletions

diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index d6b44a0..5d76851 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -188,9 +188,9 @@ void MCStreamer::InitSections(bool NoExecStack) {
   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
 }
 
-void MCStreamer::AssignSection(MCSymbol *Symbol, MCSection *Section) {
-  assert(Section);
-  Symbol->setSection(*Section);
+void MCStreamer::AssignFragment(MCSymbol *Symbol, MCFragment *Fragment) {
+  assert(Fragment);
+  Symbol->setFragment(Fragment);
 
   // As we emit symbols into a section, track the order so that they can
   // be sorted upon later. Zero is reserved to mean 'unemitted'.
@@ -200,7 +200,8 @@ void MCStreamer::AssignSection(MCSymbol *Symbol, MCSection *Section) {
 void MCStreamer::EmitLabel(MCSymbol *Symbol) {
   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
   assert(getCurrentSection().first && "Cannot emit before setting section!");
-  AssignSection(Symbol, getCurrentSection().first);
+  assert(!Symbol->getFragment() && "Unexpected fragment on symbol data!");
+  Symbol->setFragment(&getCurrentSectionOnly()->getDummyFragment());
 
   MCTargetStreamer *TS = getTargetStreamer();
   if (TS)