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, 5 deletions

diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 0f65d51bb73..50ee08fa1f9 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -180,8 +180,6 @@ void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 
-  // isSymbolLinkerVisible uses the section.
-  AssignSection(Symbol, getCurrentSection().first);
   // We have to create a new fragment if this is an atom defining symbol,
   // fragments cannot span atoms.
   if (getAssembler().isSymbolLinkerVisible(*Symbol))
@@ -415,8 +413,6 @@ void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
   if (ByteAlignment != 1)
     new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, Section);
 
-  AssignSection(Symbol, Section);
-
   MCFragment *F = new MCFillFragment(0, 0, Size, Section);
   Symbol->setFragment(F);
 
@@ -460,7 +456,8 @@ void MCMachOStreamer::FinishImpl() {
   // defining symbols.
   DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
   for (const MCSymbol &Symbol : getAssembler().symbols()) {
-    if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.getFragment()) {
+    if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.isInSection() &&
+        !Symbol.isVariable()) {
       // An atom defining symbol should never be internal to a fragment.
       assert(Symbol.getOffset() == 0 &&
              "Invalid offset in atom defining symbol!");