Add #pragma vectorize enable/disable to LLVM

The intended behaviour is to force vectorization on the presence
of the flag (either turn on or off), and to continue the behaviour
as expected in its absence. Tests were added to make sure the all
cases are covered in opt. No tests were added in other tools with
the assumption that they should use the PassManagerBuilder in the
same way.

This patch also removes the outdated -late-vectorize flag, which was
on by default and not helping much.

The pragma metadata is being attached to the same place as other loop
metadata, but nothing forbids one from attaching it to a function
(to enable #pragma optimize) or basic blocks (to hint the basic-block
vectorizers), etc. The logic should be the same all around.

Patches to Clang to produce the metadata will be produced after the
initial implementation is agreed upon and committed. Patches to other
vectorizers (such as SLP and BB) will be added once we're happy with
the pass manager changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196537 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 24 deletions

diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 24c5018d542..cd46c799829 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -33,11 +33,6 @@ RunLoopVectorization("vectorize-loops", cl::Hidden,
                      cl::desc("Run the Loop vectorization passes"));
 
 static cl::opt<bool>
-LateVectorization("late-vectorize", cl::init(true), cl::Hidden,
-                  cl::desc("Run the vectorization pasess late in the pass "
-                           "pipeline (after the inliner)"));
-
-static cl::opt<bool>
 RunSLPVectorization("vectorize-slp", cl::Hidden,
                     cl::desc("Run the SLP vectorization passes"));
 
@@ -68,7 +63,6 @@ PassManagerBuilder::PassManagerBuilder() {
     BBVectorize = RunBBVectorization;
     SLPVectorize = RunSLPVectorization;
     LoopVectorize = RunLoopVectorization;
-    LateVectorize = LateVectorization;
     RerollLoops = RunLoopRerolling;
 }
 
@@ -200,9 +194,6 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
   MPM.add(createLoopIdiomPass());             // Recognize idioms like memset.
   MPM.add(createLoopDeletionPass());          // Delete dead loops
 
-  if (!LateVectorize && LoopVectorize)
-      MPM.add(createLoopVectorizePass(DisableUnrollLoops));
-
   if (!DisableUnrollLoops)
     MPM.add(createLoopUnrollPass());          // Unroll small loops
   addExtensionsToPM(EP_LoopOptimizerEnd, MPM);
@@ -243,21 +234,18 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
   MPM.add(createCFGSimplificationPass()); // Merge & remove BBs
   MPM.add(createInstructionCombiningPass());  // Clean up after everything.
 
-  // As an experimental mode, run any vectorization passes in a separate
-  // pipeline from the CGSCC pass manager that runs iteratively with the
-  // inliner.
-  if (LateVectorize && LoopVectorize) {
-    // FIXME: This is a HACK! The inliner pass above implicitly creates a CGSCC
-    // pass manager that we are specifically trying to avoid. To prevent this
-    // we must insert a no-op module pass to reset the pass manager.
-    MPM.add(createBarrierNoopPass());
-
-    // Add the various vectorization passes and relevant cleanup passes for
-    // them since we are no longer in the middle of the main scalar pipeline.
-    MPM.add(createLoopVectorizePass(DisableUnrollLoops));
-    MPM.add(createInstructionCombiningPass());
-    MPM.add(createCFGSimplificationPass());
-  }
+  // FIXME: This is a HACK! The inliner pass above implicitly creates a CGSCC
+  // pass manager that we are specifically trying to avoid. To prevent this
+  // we must insert a no-op module pass to reset the pass manager.
+  MPM.add(createBarrierNoopPass());
+  MPM.add(createLoopVectorizePass(DisableUnrollLoops, LoopVectorize));
+  // FIXME: Because of #pragma vectorize enable, the passes below are always
+  // inserted in the pipeline, even when the vectorizer doesn't run (ex. when
+  // on -O1 and no #pragma is found). Would be good to have these two passes
+  // as function calls, so that we can only pass them when the vectorizer
+  // changed the code.
+  MPM.add(createInstructionCombiningPass());
+  MPM.add(createCFGSimplificationPass());
 
   if (!DisableUnitAtATime) {
     // FIXME: We shouldn't bother with this anymore.