Have HInstruction::StrictlyDominates compute strict dominance.

Change-Id: I3a4fa133268615fb4ce54a0bcb43e0c2458cc865

3 files changed, 11 insertions, 6 deletions

diff --git a/compiler/optimizing/graph_checker.cc b/compiler/optimizing/graph_checker.cc
index 9f40297..743ffc4 100644
--- a/compiler/optimizing/graph_checker.cc
+++ b/compiler/optimizing/graph_checker.cc
@@ -268,7 +268,7 @@ void SSAChecker::VisitInstruction(HInstruction* instruction) {
   for (HUseIterator<HInstruction> use_it(instruction->GetUses());
        !use_it.Done(); use_it.Advance()) {
     HInstruction* use = use_it.Current()->GetUser();
-    if (!use->IsPhi() && !instruction->Dominates(use)) {
+    if (!use->IsPhi() && !instruction->StrictlyDominates(use)) {
       std::stringstream error;
       error << "Instruction " << instruction->GetId()
             << " in block " << current_block_->GetBlockId()
@@ -285,7 +285,7 @@ void SSAChecker::VisitInstruction(HInstruction* instruction) {
     for (size_t i = 0, e = environment->Size(); i < e; ++i) {
       HInstruction* env_instruction = environment->GetInstructionAt(i);
       if (env_instruction != nullptr
-          && !env_instruction->Dominates(instruction)) {
+          && !env_instruction->StrictlyDominates(instruction)) {
         std::stringstream error;
         error << "Instruction " << env_instruction->GetId()
               << " in environment of instruction " << instruction->GetId()
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index aee2177..10c6014 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -472,7 +472,11 @@ bool HInstructionList::FoundBefore(const HInstruction* instruction1,
   return true;
 }
 
-bool HInstruction::Dominates(HInstruction* other_instruction) const {
+bool HInstruction::StrictlyDominates(HInstruction* other_instruction) const {
+  if (other_instruction == this) {
+    // An instruction does not strictly dominate itself.
+    return false;
+  }
   HBasicBlock* block = GetBlock();
   HBasicBlock* other_block = other_instruction->GetBlock();
   if (block != other_block) {
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index ec26c4a..7bb71b6 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -684,9 +684,10 @@ class HInstruction : public ArenaObject {
     return result;
   }
 
-  // Does this instruction dominate `other_instruction`?  Aborts if
-  // this instruction and `other_instruction` are both phis.
-  bool Dominates(HInstruction* other_instruction) const;
+  // Does this instruction strictly dominate `other_instruction`?
+  // Returns false if this instruction and `other_instruction` are the same.
+  // Aborts if this instruction and `other_instruction` are both phis.
+  bool StrictlyDominates(HInstruction* other_instruction) const;
 
   int GetId() const { return id_; }
   void SetId(int id) { id_ = id; }