diff --git a/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp b/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
index 1e2a6de572a..c37ae9919ce 100644
--- a/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
+++ b/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
@@ -620,6 +620,18 @@ bool X86ATTAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
     
     switch (ExtraCode[0]) {
     default: return true;  // Unknown modifier.
+    case 'a': // This is an address.  Currently only 'i' and 'r' are expected.
+      if (MO.isImm()) {
+        O << MO.getImm();
+        return false;
+      } else if (MO.isReg()) {
+        O << '(';
+        printOperand(MI, OpNo);
+        O << ')';
+        return false;
+      }
+      return true;
+
     case 'c': // Don't print "$" before a global var name or constant.
       if (MO.isImm())
         O << MO.getImm();
diff --git a/test/CodeGen/X86/2009-08-19-inline-asm-a-modifier.ll b/test/CodeGen/X86/2009-08-19-inline-asm-a-modifier.ll
new file mode 100644
index 00000000000..b2584a21ea0
--- /dev/null
+++ b/test/CodeGen/X86/2009-08-19-inline-asm-a-modifier.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as < %s | llc | grep {%gs:6}
+; RUN: llvm-as < %s | llc | grep {%gs:\\\(%*\\\)}
+; ModuleID = 'asm.c'
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin9.6"
+
+define i32 @main() nounwind {
+entry:
+  %asmtmp.i = tail call i16 asm "movw\09%gs:${1:a}, ${0:w}", "=r,ir,~{dirflag},~{fpsr},~{flags}"(i32 6) nounwind ; <i16> [#uses=1]
+  %0 = zext i16 %asmtmp.i to i32                  ; <i32> [#uses=1]
+  ret i32 %0
+}
+
+define zeroext i16 @readgsword2(i32 %address) nounwind {
+entry:
+  %asmtmp = tail call i16 asm "movw\09%gs:${1:a}, ${0:w}", "=r,ir,~{dirflag},~{fpsr},~{flags}"(i32 %address) nounwind ; <i16> [#uses=1]
+  ret i16 %asmtmp
+}