[LPM] Actually test what the O2 pass pipeline consists of in key places,

especially the *structure* of it with respect to various pass managers.

This uncovers an absolute horror show of problems. This test shows just
how bad PR24804 is: we have a totaly of *seven* loop pass managers in
the main optimization pipeline.

I've tried to comment the various bits to the best of my knowledge, but
more enhancements here would be great.

Also great would be folks adding various test for other pipelines, I'm
focused on trying to fix the O2 pipeline. I just wanted a test to show
what I'm changing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261305 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 101 insertions, 0 deletions

diff --git a/test/Other/pass-pipelines.ll b/test/Other/pass-pipelines.ll
new file mode 100644
index 00000000000..905dc73299b
--- /dev/null
+++ b/test/Other/pass-pipelines.ll
@@ -0,0 +1,101 @@
+; Test the particular pass pipelines have the expected structure. This is
+; particularly important in order to check that the implicit scheduling of the
+; legacy pass manager doesn't introduce unexpected structural changes in the
+; pass pipeline.
+;
+; RUN: opt -disable-output -disable-verify -debug-pass=Structure \
+; RUN:     -O2 %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefix=CHECK-O2
+;
+; In the first pipeline there should just be a function pass manager, no other
+; pass managers.
+; CHECK-O2: Pass Arguments:
+; CHECK-O2-NOT: Manager
+; CHECK-O2: FunctionPass Manager
+; CHECK-O2-NOT: Manager
+;
+; CHECK-O2: Pass Arguments:
+; CHECK-O2: ModulePass Manager
+; CHECK-O2-NOT: Manager
+; First function pass pipeline just does early opts.
+; CHECK-O2: FunctionPass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: It's a bit odd to do dead arg elim in the middle of early opts...
+; CHECK-O2: Dead Argument Elimination
+; CHECK-O2-NEXT: FunctionPass Manager
+; CHECK-O2-NOT: Manager
+; Very carefully asert the CGSCC pass pipeline as it is fragile and unusually
+; susceptible to phase ordering issues.
+; CHECK-O2: CallGraph Construction
+; CHECK-O2-NEXT: Globals Alias Analysis
+; CHECK-O2-NEXT: Call Graph SCC Pass Manager
+; CHECK-O2-NEXT: Remove unused exception handling info
+; CHECK-O2-NEXT: Function Integration/Inlining
+; CHECK-O2-NEXT: Deduce function attributes
+; Next up is the main function pass pipeline. It shouldn't be split up and
+; should contain the main loop pass pipeline as well.
+; CHECK-O2-NEXT: FunctionPass Manager
+; CHECK-O2-NOT: Manager
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: We shouldn't have this extra loop pass manager!
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: Yet another pointless loop pass manager!
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: We shouldn't be pulling out to simplify-cfg and instcombine and
+; causing new loop pass managers.
+; CHECK-O2: Simplify the CFG
+; CHECK-O2-NOT: Manager
+; CHECK-O2: Combine redundant instructions
+; CHECK-O2-NOT: Manager
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: Yet another pointless loop pass manager!
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: Yet another pointless loop pass manager!
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NOT: Manager
+; FIXME: It isn't clear that we need yet another loop pass pipeline
+; and run of LICM here.
+; CHECK-O2-NOT: Manager
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NEXT: Loop Invariant Code Motion
+; CHECK-O2-NOT: Manager
+; Next we break out of the main Function passes inside the CGSCC pipeline with
+; a barrier pass.
+; CHECK-O2: A No-Op Barrier Pass
+; CHECK-O2-NOT: Manager
+; Next is the late function pass pipeline.
+; CHECK-O2: FunctionPass Manager
+; CHECK-O2-NOT: Manager
+; We rotate loops prior to vectorization.
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NEXT: Rotate Loops
+; CHECK-O2-NOT: Manager
+; CHECK-O2: Loop Vectorization
+; CHECK-O2-NOT: Manager
+; CHECK-O2: SLP Vectorizer
+; CHECK-O2-NOT: Manager
+; After vectorization we do partial unrolling.
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NEXT: Unroll loops
+; CHECK-O2-NOT: Manager
+; After vectorization and unrolling we try to do any cleanup of inserted code,
+; including a run of LICM. This shouldn't run in the same loop pass manager as
+; the runtime unrolling though.
+; CHECK-O2: Loop Pass Manager
+; CHECK-O2-NEXT: Loop Invariant Code Motion
+; CHECK-O2-NOT: Manager
+;
+; FIXME: There really shouldn't be another pass manager, especially one that
+; just builds the domtree. It doesn't even run the verifier.
+; CHECK-O2: Pass Arguments:
+; CHECK-O2-NEXT: FunctionPass Manager
+; CHECK-O2-NEXT: Dominator Tree Construction
+
+define void @foo() {
+  ret void
+}