[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, 20 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h
index c4e69843615..3f11dcb5164 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h
@@ -26,14 +26,18 @@
 #define LLVM_TRANSFORMS_VECTORIZE_VPLAN_VPLANHCFGBUILDER_H
 
 #include "VPlan.h"
+#include "VPlanDominatorTree.h"
 #include "VPlanVerifier.h"
 
 namespace llvm {
 
 class Loop;
+class VPlanTestBase;
 
 /// Main class to build the VPlan H-CFG for an incoming IR.
 class VPlanHCFGBuilder {
+  friend VPlanTestBase;
+
 private:
   // The outermost loop of the input loop nest considered for vectorization.
   Loop *TheLoop;
@@ -41,14 +45,27 @@ private:
   // Loop Info analysis.
   LoopInfo *LI;
 
+  // The VPlan that will contain the H-CFG we are building.
+  VPlan &Plan;
+
   // VPlan verifier utility.
   VPlanVerifier Verifier;
 
+  // Dominator analysis for VPlan plain CFG to be used in the
+  // construction of the H-CFG. This analysis is no longer valid once regions
+  // are introduced.
+  VPDominatorTree VPDomTree;
+
+  /// Build plain CFG for TheLoop. Return a new VPRegionBlock (TopRegion)
+  /// enclosing the plain CFG.
+  VPRegionBlock *buildPlainCFG();
+
 public:
-  VPlanHCFGBuilder(Loop *Lp, LoopInfo *LI) : TheLoop(Lp), LI(LI) {}
+  VPlanHCFGBuilder(Loop *Lp, LoopInfo *LI, VPlan &P)
+      : TheLoop(Lp), LI(LI), Plan(P) {}
 
-  /// Build H-CFG for TheLoop and update \p Plan accordingly.
-  void buildHierarchicalCFG(VPlan &Plan);
+  /// Build H-CFG for TheLoop and update Plan accordingly.
+  void buildHierarchicalCFG();
 };
 } // namespace llvm