dart2js: improve ssa utilization of bool value types

pkg/compiler/lib/src/ssa/optimize.dart

Index: pkg/compiler/lib/src/ssa/optimize.dart
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 07611f654a3292066d02ec241076f47e28dc7c3b..d4a55a4ee065f519ffdaa03c296d2ef8f77c112f 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -200,6 +200,24 @@ class SsaInstructionSimplifier extends HBaseVisitor
     return node;
   }
 
+  void replaceUsesWithConstant(HInstruction known) {
+    if (known.isValue() && !known.canBeNull()) {
+      ValueTypeMask valueMask = known.instructionType;
+      if (valueMask.value.isBool) {
+        bool knownValue = valueMask.value.isTrue;
+        var users = new List.from(known.usedBy);
+        users.forEach((HInstruction user) {

[sra1, 2015/09/30 16:49:39]

maybe just write:

for (HInstruction user in known.usedBy.toList()) {
}

[Harry Terkelsen, 2015/09/30 18:39:26]

Done.

+          user.changeUse(known, graph.addConstantBool(knownValue, compiler));

[sra1, 2015/09/30 16:49:39]

Factor this into (1) finding the HConstant (if any) (2) doing the replacement
(which can reuse the constant).

If (1) is extended (replace ints, small strings, etc) this will be cleaner.

First check usedBy is not empty (it will be on second pass) to avoid computing
the constant.

[Harry Terkelsen, 2015/09/30 18:39:26]

Done.

+        });
+      }
+    }
+  }
+
+  HInstruction visitParameterValue(HParameterValue node) {
+    replaceUsesWithConstant(node);

[sra1, 2015/09/30 16:49:40]

Reading this I ask 'why'?
Maybe call it propagateConstantValueToUses

[Harry Terkelsen, 2015/09/30 18:39:26]

Done.

+    return node;
+  }
+
   HInstruction visitBoolify(HBoolify node) {
     List<HInstruction> inputs = node.inputs;
     assert(inputs.length == 1);
@@ -402,6 +420,7 @@ class SsaInstructionSimplifier extends HBaseVisitor
         }
       }
     }
+    replaceUsesWithConstant(node);

[sra1, 2015/09/30 16:49:40]

Any reason not to do this first?
It might require more mock_library changes.

[Harry Terkelsen, 2015/09/30 18:39:26]

Done.

     return node;
   }
 
@@ -811,6 +830,7 @@ class SsaInstructionSimplifier extends HBaseVisitor
       if (folded != node) return folded;
     }
     HInstruction receiver = node.getDartReceiver(compiler);
+    replaceUsesWithConstant(node);

[sra1, 2015/09/30 16:49:39]

Any reason not to do this first?
We might know we are calling (const EmptyIterator()).isEmpty; which returns
true.

[Harry Terkelsen, 2015/09/30 18:39:26]

Done.

     Element field = findConcreteFieldForDynamicAccess(
         receiver, node.selector);
     if (field == null) return node;
@@ -867,6 +887,7 @@ class SsaInstructionSimplifier extends HBaseVisitor
   }
 
   HInstruction visitInvokeStatic(HInvokeStatic node) {
+    replaceUsesWithConstant(node);
     if (node.element == backend.getCheckConcurrentModificationError()) {
       if (node.inputs.length == 2) {
         HInstruction firstArgument = node.inputs[0];
@@ -1306,13 +1327,6 @@ class SsaLiveBlockAnalyzer extends HBaseVisitor {
       } else {
         markBlockLive(instruction.elseBlock);
       }
-    } else if (condition.isValue()) {
-      ValueTypeMask valueType = condition.instructionType;
-      if (valueType.value == true) {
-        markBlockLive(instruction.thenBlock);
-      } else {
-        markBlockLive(instruction.elseBlock);
-      }
     } else {
       visitControlFlow(instruction);
     }