[v8] Add --maglev-untagged-phis with 0.5 probability

Change-Id: I9f2aedf60a7d3d8eec7011243e6ddac5af94aa74
Reviewed-on: https://chrome-internal-review.googlesource.com/c/v8/fuzzilli/+/9099036
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Matthias Liedtke <mliedtke@google.com>
Reviewed-by: Darius Mercadier <dmercadier@google.com>

Author: marjakh

Sources/Fuzzilli/Profiles/V8CommonProfile.swift

@@ -946,6 +946,9 @@ public func v8ProcessArgs(randomize: Bool, forSandbox: Bool) -> [String] {
     }
 
     if !args.contains("--no-maglev") {
+        if probability(0.5) {
+            args.append("--maglev-untagged-phis")
+        }
         if probability(0.25) {
             args.append("--maglev-future")
         }
@@ -1152,7 +1155,6 @@ public func v8ProcessArgs(randomize: Bool, forSandbox: Bool) -> [String] {
         chooseBooleanFlag("maglev-range-analysis")
         chooseBooleanFlag("maglev-escape-analysis")
         chooseBooleanFlag("maglev-licm")
-        chooseBooleanFlag("maglev-untagged-phis")
 
         // Compiler related flags
         chooseBooleanFlag("turbo-move-optimization")