llc: Add a 'run-pass' option.

This commit adds a 'run-pass' option to llc, which instructs the compiler to run
one specific code generation pass only.

Llc already has the 'start-after' and the 'stop-after' options, and this new
option complements the other two by making it easier to write tests that want
to invoke a single pass only.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10776


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241476 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/CommandFlags.h

@@ -206,6 +206,10 @@ cl::opt<std::string> StartAfter("start-after",
                           cl::value_desc("pass-name"),
                           cl::init(""));
 
+cl::opt<std::string>
+    RunPass("run-pass", cl::desc("Run compiler only for one specific pass"),
+            cl::value_desc("pass-name"), cl::init(""));
+
 cl::opt<bool> DataSections("data-sections",
                            cl::desc("Emit data into separate sections"),
                            cl::init(false));