Add a flag to defer vectorization into a phase after the inliner and its

CGSCC pass manager. This should insulate the inlining decisions from the
vectorization decisions, however it may have both compile time and code
size problems so it is just an experimental option right now.

Adding this based on a discussion with Arnold and it seems at least
worth having this flag for us to both run some experiments to see if
this strategy is workable. It may solve some of the regressions seen
with the loop vectorizer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184698 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 66 insertions, 16 deletions

diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 9d88608..1917cc8 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -33,6 +33,11 @@ RunLoopVectorization("vectorize-loops",
                      cl::desc("Run the Loop vectorization passes"));
 
 static cl::opt<bool>
+LateVectorization("late-vectorize", cl::init(false), cl::Hidden,
+                  cl::desc("Run the vectorization pasess late in the pass "
+                           "pipeline (after the inliner)"));
+
+static cl::opt<bool>
 RunSLPVectorization("vectorize-slp",
                     cl::desc("Run the SLP vectorization passes"));
 
@@ -59,6 +64,7 @@ PassManagerBuilder::PassManagerBuilder() {
     BBVectorize = RunBBVectorization;
     SLPVectorize = RunSLPVectorization;
     LoopVectorize = RunLoopVectorization;
+    LateVectorize = LateVectorization;
 }
 
 PassManagerBuilder::~PassManagerBuilder() {
@@ -189,8 +195,8 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
   MPM.add(createLoopIdiomPass());             // Recognize idioms like memset.
   MPM.add(createLoopDeletionPass());          // Delete dead loops
 
-  if (LoopVectorize && OptLevel > 1 && SizeLevel < 2)
-    MPM.add(createLoopVectorizePass());
+  if (!LateVectorize && LoopVectorize && OptLevel > 1 && SizeLevel < 2)
+      MPM.add(createLoopVectorizePass());
 
   if (!DisableUnrollLoops)
     MPM.add(createLoopUnrollPass());          // Unroll small loops
@@ -210,26 +216,70 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
 
   addExtensionsToPM(EP_ScalarOptimizerLate, MPM);
 
-  if (SLPVectorize)
-    MPM.add(createSLPVectorizerPass());     // Vectorize parallel scalar chains.
-
-  if (BBVectorize) {
-    MPM.add(createBBVectorizePass());
-    MPM.add(createInstructionCombiningPass());
-    if (OptLevel > 1 && UseGVNAfterVectorization)
-      MPM.add(createGVNPass());                   // Remove redundancies
-    else
-      MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
-
-    // BBVectorize may have significantly shortened a loop body; unroll again.
-    if (!DisableUnrollLoops)
-      MPM.add(createLoopUnrollPass());
+  if (!LateVectorize) {
+    if (SLPVectorize)
+      MPM.add(createSLPVectorizerPass());   // Vectorize parallel scalar chains.
+
+    if (BBVectorize) {
+      MPM.add(createBBVectorizePass());
+      MPM.add(createInstructionCombiningPass());
+      if (OptLevel > 1 && UseGVNAfterVectorization)
+        MPM.add(createGVNPass());           // Remove redundancies
+      else
+        MPM.add(createEarlyCSEPass());      // Catch trivial redundancies
+
+      // BBVectorize may have significantly shortened a loop body; unroll again.
+      if (!DisableUnrollLoops)
+        MPM.add(createLoopUnrollPass());
+    }
   }
 
   MPM.add(createAggressiveDCEPass());         // Delete dead instructions
   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) {
+    // 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.
+    if (LoopVectorize && OptLevel > 1 && SizeLevel < 2) {
+      MPM.add(createLoopVectorizePass());
+
+      if (!DisableUnrollLoops)
+        MPM.add(createLoopUnrollPass());    // Unroll small loops
+
+      // FIXME: Is this necessary/useful? Should we also do SimplifyCFG?
+      MPM.add(createInstructionCombiningPass());
+    }
+
+    if (SLPVectorize) {
+      MPM.add(createSLPVectorizerPass());   // Vectorize parallel scalar chains.
+
+      // FIXME: Is this necessary/useful? Should we also do SimplifyCFG?
+      MPM.add(createInstructionCombiningPass());
+    }
+
+    if (BBVectorize) {
+      MPM.add(createBBVectorizePass());
+      MPM.add(createInstructionCombiningPass());
+      if (OptLevel > 1 && UseGVNAfterVectorization)
+        MPM.add(createGVNPass());           // Remove redundancies
+      else
+        MPM.add(createEarlyCSEPass());      // Catch trivial redundancies
+
+      // BBVectorize may have significantly shortened a loop body; unroll again.
+      if (!DisableUnrollLoops)
+        MPM.add(createLoopUnrollPass());
+    }
+  }
+
   if (!DisableUnitAtATime) {
     // FIXME: We shouldn't bother with this anymore.
     MPM.add(createStripDeadPrototypesPass()); // Get rid of dead prototypes