Shorten live ranges for arguments to runtime calls.

src/lithium.h

Index: src/lithium.h
diff --git a/src/lithium.h b/src/lithium.h
index a2f9df0fdf802060d87565eb9570605e49a8bd46..d85a87c12e9fa1848858733b570ddd8f4387277e 100644
--- a/src/lithium.h
+++ b/src/lithium.h
@@ -536,10 +536,12 @@ class ShallowIterator BASE_EMBEDDED {
   inline LEnvironment* env() { return env_; }
 
  private:
+  inline bool ShouldSkip(LOperand* op) {
+    return op == NULL || op->IsConstantOperand() || op->IsArgument();

[fschneider, 2011/02/21 17:02:01]

Just wondering: Was this already a problem before to have LArgument operands in
the enumeration of environment uses not skipped?

+  }
+
   inline int AdvanceToNext(int start) {
-    while (start < limit_ &&
-           (env_->values()->at(start) == NULL ||
-            env_->values()->at(start)->IsConstantOperand())) {
+    while (start < limit_ && ShouldSkip(env_->values()->at(start))) {
       start++;
     }
     return start;