MIR Serialization: Report an error when machine functions have the same name.

This commit reports an error when the MIR parser encounters a machine
function with the name that is the same as the name of a different
machine function.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10130

llvm-svn: 239774
diff --git a/llvm/test/CodeGen/MIR/machine-function-redefinition-error.mir b/llvm/test/CodeGen/MIR/machine-function-redefinition-error.mir
new file mode 100644
index 0000000..be84161
--- /dev/null
+++ b/llvm/test/CodeGen/MIR/machine-function-redefinition-error.mir
@@ -0,0 +1,10 @@
+# RUN: not llc -start-after branch-folder -stop-after branch-folder -o /dev/null %s 2>&1 | FileCheck %s
+# This test ensures that the machine function errors are reported correctly.
+
+---
+name:            foo
+...
+---
+# CHECK: redefinition of machine function 'foo'
+name:            foo
+...