Turn stack check elimination into proper HPhase.

src/hydrogen-sce.cc

Index: src/hydrogen-sce.cc
diff --git a/src/hydrogen-escape-analysis.cc b/src/hydrogen-sce.cc
similarity index 63%
copy from src/hydrogen-escape-analysis.cc
copy to src/hydrogen-sce.cc
index e852fb8d6d75d7756df6e4e03399bfb8789d4c76..a6995f647afc00437783f057110c7654a28265c3 100644
--- a/src/hydrogen-escape-analysis.cc
+++ b/src/hydrogen-sce.cc
@@ -25,42 +25,38 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#include "hydrogen-escape-analysis.h"
+#include "hydrogen-sce.h"
+#include "v8.h"
 
 namespace v8 {
 namespace internal {
 
-
-void HEscapeAnalysisPhase::CollectIfNoEscapingUses(HInstruction* instr) {
-  for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
-    HValue* use = it.value();
-    if (use->HasEscapingOperandAt(it.index())) {
-      if (FLAG_trace_escape_analysis) {
-        PrintF("#%d (%s) escapes through #%d (%s) @%d\n", instr->id(),
-               instr->Mnemonic(), use->id(), use->Mnemonic(), it.index());
-      }
-      return;
-    }
-  }
-  if (FLAG_trace_escape_analysis) {
-    PrintF("#%d (%s) is being captured\n", instr->id(), instr->Mnemonic());
-  }
-  captured_.Add(instr, zone());
-}
-
-
-void HEscapeAnalysisPhase::CollectCapturedValues() {
-  int block_count = graph()->blocks()->length();
-  for (int i = 0; i < block_count; ++i) {
+void HStackCheckEliminationPhase::Run() {
+  // For each loop block walk the dominator tree from the backwards branch to
+  // the loop header. If a call instruction is encountered the backwards branch
+  // is dominated by a call and the stack check in the backwards branch can be
+  // removed.
+  for (int i = 0; i < graph()->blocks()->length(); i++) {
     HBasicBlock* block = graph()->blocks()->at(i);
-    for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
-      HInstruction* instr = it.Current();
-      if (instr->IsAllocate() || instr->IsAllocateObject()) {
-        CollectIfNoEscapingUses(instr);
+    if (block->IsLoopHeader()) {
+      HBasicBlock* back_edge = block->loop_information()->GetLastBackEdge();
+      HBasicBlock* dominator = back_edge;
+      while (true) {
+        for (HInstructionIterator it(dominator); !it.Done(); it.Advance()) {
+          if (it.Current()->IsCall()) {
+            block->loop_information()->stack_check()->Eliminate();
+            break;
+          }
+        }
+
+        // Done when the loop header is processed.
+        if (dominator == block) break;
+
+        // Move up the dominator tree.
+        dominator = dominator->dominator();
       }
     }
   }
 }
 
-
 } }  // namespace v8::internal