More zero-check eliminator improvements

[Gary Benson]

Hi all,

This patch allows Shark's zero-check eliminator to eliminate checks
through phid states.  Previously, zero-checked status was lost
whenever the flow passed through a phi, meaning checks were performed
unnecessarily.

Cheers,
Gary

-- 
http://gbenson.net/
-------------- next part --------------
diff -r 052feb41dea9 ports/hotspot/src/share/vm/shark/sharkState.cpp
--- a/ports/hotspot/src/share/vm/shark/sharkState.cpp	Tue Mar 17 13:49:28 2009 +0000
+++ b/ports/hotspot/src/share/vm/shark/sharkState.cpp	Mon Mar 23 09:27:43 2009 +0000
@@ -149,30 +149,31 @@
     SharkValue *this_value = this->local(i);
     SharkValue *other_value = other->local(i);
     assert((this_value == NULL) == (other_value == NULL), "should be");
-    if (this_value == other_value)
-      continue;
+    set_local(i, this_value->merge(other_value));
+//     if (this_value == other_value)
+//       continue;
 
-    if (this_value->is_address()) {
-      assert(other_value->is_address(), "should be");
+//     if (this_value->is_address()) {
+//       assert(other_value->is_address(), "should be");
 
-      int bci = this_value->address_value();
-      assert(bci == other_value->address_value(), "should be");
+//       int bci = this_value->address_value();
+//       assert(bci == other_value->address_value(), "should be");
 
-      set_local(i, SharkValue::address_constant(bci));
-    }
-    else {
-      ciType *this_type = this_value->type();
-      assert(this_type == other_value->type(), "should be");
+//       set_local(i, SharkValue::address_constant(bci));
+//     }
+//     else {
+//       ciType *this_type = this_value->type();
+//       assert(this_type == other_value->type(), "should be");
 
-      bool this_checked = this_value->zero_checked();
-      assert(this_checked == other_value->zero_checked(), "should be");
+//       bool this_checked = this_value->zero_checked();
+//       assert(this_checked == other_value->zero_checked(), "should be");
 
-      snprintf(name, sizeof(name), "local_%d_", i);
-      phi = builder()->CreatePHI(SharkType::to_stackType(this_type), name);
-      phi->addIncoming(this_value->generic_value(), this_block);
-      phi->addIncoming(other_value->generic_value(), other_block);
-      set_local(i, SharkValue::create_generic(this_type, phi, this_checked));
-    }
+//       snprintf(name, sizeof(name), "local_%d_", i);
+//       phi = builder()->CreatePHI(SharkType::to_stackType(this_type), name);
+//       phi->addIncoming(this_value->generic_value(), this_block);
+//       phi->addIncoming(other_value->generic_value(), other_block);
+//       set_local(i, SharkValue::create_generic(this_type, phi, this_checked));
+//     }
   }
 
   // Expression stack
@@ -181,30 +182,7 @@
     SharkValue *this_value = this->stack(i);
     SharkValue *other_value = other->stack(i);
     assert((this_value == NULL) == (other_value == NULL), "should be");
-    if (this_value == other_value)
-      continue;
-
-    if (this_value->is_address()) {
-      assert(other_value->is_address(), "should be");
-
-      int bci = this_value->address_value();
-      assert(bci == other_value->address_value(), "should be");
-
-      set_stack(i, SharkValue::address_constant(bci));
-    }
-    else {
-      ciType *this_type = this_value->type();
-      assert(this_type == other_value->type(), "should be");
-
-      bool this_checked = this_value->zero_checked();
-      assert(this_checked == other_value->zero_checked(), "should be");
-
-      snprintf(name, sizeof(name), "stack_%d_", i);
-      phi = builder()->CreatePHI(SharkType::to_stackType(this_type), name);
-      phi->addIncoming(this_value->generic_value(), this_block);
-      phi->addIncoming(other_value->generic_value(), other_block);
-      set_stack(i, SharkValue::create_generic(this_type, phi, this_checked));
-    }
+    set_stack(i, this_value->merge(other_value));
   }
 }