Add support for the 'X' inline asm operand modifier.

Patch by Jack Carter.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156577 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/Mips/inlineasm-operand-code.ll b/test/CodeGen/Mips/inlineasm-operand-code.ll
new file mode 100644
index 0000000..4568a84
--- /dev/null
+++ b/test/CodeGen/Mips/inlineasm-operand-code.ll
@@ -0,0 +1,15 @@
+; Positive test for inline register constraints
+;
+; RUN: llc -march=mipsel < %s  | FileCheck %s
+
+define i32 @main() nounwind {
+entry:
+
+; X with -3
+;CHECK:	#APP
+;CHECK:	addi ${{[0-9]+}},${{[0-9]+}},0xfffffffffffffffd
+;CHECK:	#NO_APP
+  tail call i32 asm sideeffect "addi $0,$1,${2:X}", "=r,r,I"(i32 7, i32 -3) nounwind
+
+  ret i32 0
+}