Disable unrolling in the loop vectorizer when disabled in the pass manager

When unrolling is disabled in the pass manager, the loop vectorizer should also
not unroll loops. This will allow the -fno-unroll-loops option in Clang to
behave as expected (even for vectorizable loops). The loop vectorizer's
-force-vector-unroll option will (continue to) override the pass-manager
setting (including -force-vector-unroll=0 to force use of the internal
auto-selection logic).

In order to test this, I added a flag to opt (-disable-loop-unrolling) to force
disable unrolling through opt (the analog of -fno-unroll-loops in Clang). Also,
this fixes a small bug in opt where the loop vectorizer was enabled only after
the pass manager populated the queue of passes (the global_alias.ll test needed
a slight update to the RUN line as a result of this fix).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189499 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 743dc42343..d4c0c2caea 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -196,7 +196,7 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
   MPM.add(createLoopDeletionPass());          // Delete dead loops
 
   if (!LateVectorize && LoopVectorize)
-      MPM.add(createLoopVectorizePass());
+      MPM.add(createLoopVectorizePass(DisableUnrollLoops));
 
   if (!DisableUnrollLoops)
     MPM.add(createLoopUnrollPass());          // Unroll small loops
@@ -250,7 +250,7 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
     // Add the various vectorization passes and relevant cleanup passes for
     // them since we are no longer in the middle of the main scalar pipeline.
     if (LoopVectorize) {
-      MPM.add(createLoopVectorizePass());
+      MPM.add(createLoopVectorizePass(DisableUnrollLoops));
 
       if (!DisableUnrollLoops)
         MPM.add(createLoopUnrollPass());    // Unroll small loops