Extend TargetPassConfig to allow running only a subset of the normal passes.

This is still a work in progress but I believe it is currently good enough
to fix PR13122 "Need unit test driver for codegen IR passes".  For example,
you can run llc with -stop-after=loop-reduce to have it dump out the IR after
running LSR.  Serializing machine-level IR is not yet supported but we have
some patches in progress for that.

The plan is to serialize the IR to a YAML file, containing separate sections
for the LLVM IR, machine-level IR, and whatever other info is needed.  Chad
suggested that we stash the stop-after pass in the YAML file and use that
instead of the start-after option to figure out where to restart the
compilation.  I think that's a great idea, but since it's not implemented yet
I put the -start-after option into this patch for testing purposes.

llvm-svn: 159570

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Generic/stop-after.ll b/llvm/test/CodeGen/Generic/stop-after.ll
new file mode 100644
index 00000000000..557e097840a
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/stop-after.ll
@@ -0,0 +1,10 @@
+; RUN: llc < %s -debug-pass=Structure -stop-after=loop-reduce -o /dev/null 2>&1 | FileCheck %s -check-prefix=STOP
+; RUN: llc < %s -debug-pass=Structure -start-after=loop-reduce -o /dev/null 2>&1 | FileCheck %s -check-prefix=START
+
+; STOP: -loop-reduce -print-module
+; STOP: Loop Strength Reduction
+; STOP-NEXT: Machine Function Analysis
+
+; START: -machine-branch-prob -gc-lowering
+; START: FunctionPass Manager
+; START-NEXT: Lower Garbage Collection Instructions