[Dominators] Make IsPostDominator a template parameter

Summary:
DominatorTreeBase used to have IsPostDominators (bool) member to indicate if the tree is a dominator or a postdominator tree. This made it possible to switch between the two 'modes' at runtime, but it isn't used in practice anywhere.

This patch makes IsPostDominator a template argument. This way, it is easier to switch between different algorithms at compile-time based on this argument and design external utilities around it. It also makes it impossible to incidentally assign a postdominator tree to a dominator tree (and vice versa), and to further simplify template code in GenericDominatorTreeConstruction.

Reviewers: dberlin, sanjoy, davide, grosser

Reviewed By: dberlin

Subscribers: mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D35315

llvm-svn: 308040

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/MachinePostDominators.cpp b/llvm/lib/CodeGen/MachinePostDominators.cpp
index c3f6e9249e7..488377998cb 100644
--- a/llvm/lib/CodeGen/MachinePostDominators.cpp
+++ b/llvm/lib/CodeGen/MachinePostDominators.cpp
@@ -16,6 +16,10 @@
 
 using namespace llvm;
 
+namespace llvm {
+template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTreeBase
+}
+
 char MachinePostDominatorTree::ID = 0;
 
 //declare initializeMachinePostDominatorTreePass
@@ -24,8 +28,7 @@ INITIALIZE_PASS(MachinePostDominatorTree, "machinepostdomtree",
 
 MachinePostDominatorTree::MachinePostDominatorTree() : MachineFunctionPass(ID) {
   initializeMachinePostDominatorTreePass(*PassRegistry::getPassRegistry());
-  DT = new DominatorTreeBase<MachineBasicBlock>(true); //true indicate
-                                                       // postdominator
+  DT = new PostDomTreeBase<MachineBasicBlock>();
 }
 
 FunctionPass *