[VPlan] Introduce VPlan-based dominator analysis.

The patch introduces dominator analysis for VPBlockBases and extend
VPlan's GraphTraits specialization with the required interfaces. Dominator
analysis will be necessary to perform some H-CFG transformations and
to introduce VPLoopInfo (LoopInfo analysis on top of the VPlan representation).

Reviewers: fhahn, rengolin, mkuper, hfinkel, mssimpso

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D48815

llvm-svn: 338310

1 files changed, 12 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
index 08129b74cdd..26e112e02db 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
@@ -324,13 +324,22 @@ VPRegionBlock *PlainCFGBuilder::buildPlainCFG() {
   return TopRegion;
 }
 
+VPRegionBlock *VPlanHCFGBuilder::buildPlainCFG() {
+  PlainCFGBuilder PCFGBuilder(TheLoop, LI, Plan);
+  return PCFGBuilder.buildPlainCFG();
+}
+
 // Public interface to build a H-CFG.
-void VPlanHCFGBuilder::buildHierarchicalCFG(VPlan &Plan) {
+void VPlanHCFGBuilder::buildHierarchicalCFG() {
   // Build Top Region enclosing the plain CFG and set it as VPlan entry.
-  PlainCFGBuilder PCFGBuilder(TheLoop, LI, Plan);
-  VPRegionBlock *TopRegion = PCFGBuilder.buildPlainCFG();
+  VPRegionBlock *TopRegion = buildPlainCFG();
   Plan.setEntry(TopRegion);
   LLVM_DEBUG(Plan.setName("HCFGBuilder: Plain CFG\n"); dbgs() << Plan);
 
   Verifier.verifyHierarchicalCFG(TopRegion);
+
+  // Compute plain CFG dom tree for VPLInfo.
+  VPDomTree.recalculate(*TopRegion);
+  LLVM_DEBUG(dbgs() << "Dominator Tree after building the plain CFG.\n";
+             VPDomTree.print(dbgs()));
 }