llc: Add support for -run-pass none

This does not schedule any passes besides the ones necessary to
construct and print the machine function. This is useful to test .mir
file reading and printing.

Differential Revision: http://reviews.llvm.org/D22432

llvm-svn: 275664
diff --git a/llvm/test/CodeGen/MIR/Generic/machine-basic-block-ir-block-reference.mir b/llvm/test/CodeGen/MIR/Generic/machine-basic-block-ir-block-reference.mir
index 22af270..a5737c2 100644
--- a/llvm/test/CodeGen/MIR/Generic/machine-basic-block-ir-block-reference.mir
+++ b/llvm/test/CodeGen/MIR/Generic/machine-basic-block-ir-block-reference.mir
@@ -1,4 +1,4 @@
-# RUN: llc -start-after branch-folder -stop-after branch-folder -o - %s 2>&1 | FileCheck %s
+# RUN: llc -run-pass none -o - %s 2>&1 | FileCheck %s
 # This test ensures that the MIR parser preserves unnamed LLVM IR block
 # references.