Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -3579,11 +3579,7 @@
   if (Parser.parseExpression(Value))
     return reportParseError("expected valid expression after comma");
 
-  // Check if the Name already exists as a symbol.
-  MCSymbol *Sym = getContext().LookupSymbol(Name);
-  if (Sym)
-    return reportParseError("symbol already defined");
-  Sym = getContext().GetOrCreateSymbol(Name);
+  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
   Sym->setVariableValue(Value);
 
   return false;
Index: test/MC/Mips/set-defined-symbol.s
===================================================================
--- /dev/null
+++ test/MC/Mips/set-defined-symbol.s
@@ -0,0 +1,18 @@
+# RUN: llvm-mc %s -arch=mips -mcpu=mips32 -filetype=obj -o - | \
+# RUN:   llvm-objdump -d -r -arch=mips - | FileCheck %s
+
+  .global foo
+  .weak bar
+  .set bar, b
+  .set foo, b
+  .set foo, a
+a:
+  nop
+# CHECK-NOT: a:
+# CHECK: foo:
+
+b:
+  nop
+# CHECK-NOT: b:
+# CHECK-NOT: foo:
+# CHECK: bar: