Correctly handle an ELF symbol defined with "a = b + expr".

We were marking the symbol as absolute instead of computing b's offset + the
expression value.

This fixes pr19126.

llvm-svn: 203962

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCSymbol.cpp b/llvm/lib/MC/MCSymbol.cpp
index 24165254e56..d0283a635be 100644
--- a/llvm/lib/MC/MCSymbol.cpp
+++ b/llvm/lib/MC/MCSymbol.cpp
@@ -9,6 +9,7 @@
 
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCValue.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
@@ -51,6 +52,22 @@ const MCSymbol &MCSymbol::AliasedSymbol() const {
   return *S;
 }
 
+const MCSymbol *MCSymbol::getBaseSymbol(const MCAsmLayout &Layout) const {
+  if (!isVariable())
+    return this;
+
+  const MCExpr *Expr = getVariableValue();
+  MCValue Value;
+  if (!Expr->EvaluateAsRelocatable(Value, &Layout))
+    return nullptr;
+
+  if (Value.getSymB())
+    return nullptr;
+  if (const MCSymbolRefExpr *A = Value.getSymA())
+    return &A->getSymbol();
+  return nullptr;
+}
+
 void MCSymbol::setVariableValue(const MCExpr *Value) {
   assert(!IsUsed && "Cannot set a variable that has already been used.");
   assert(Value && "Invalid variable value!");