[regexp] Turn on regexp tier-up with ticks = 1

This CL enables regexp interpreter and tier-up to the compiler after one
execution by setting the --regexp-tier-up flag to true by default. The
number of times a regexp is interpreted before tiering-up is controlled
by the --regexp-tier-up-ticks flag which is already set to 1 by default.

Change-Id: I79ff7fcd159f50f2f5351b339d8ffb21af039a86
Bug: v8:9566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1816501Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Ana Pesko <anapesko@google.com>
Cr-Commit-Position: refs/heads/master@{#63905}

src/flags/flag-definitions.h

@@ -1268,7 +1268,7 @@ DEFINE_UINT(serialization_chunk_size, 4096,
 DEFINE_BOOL(regexp_optimization, true, "generate optimized regexp code")
 DEFINE_BOOL(regexp_mode_modifiers, false, "enable inline flags in regexp.")
 DEFINE_BOOL(regexp_interpret_all, false, "interpret all regexp code")
-DEFINE_BOOL(regexp_tier_up, false,
+DEFINE_BOOL(regexp_tier_up, true,
             "enable regexp interpreter and tier up to the compiler after the "
             "number of executions set by the tier up ticks flag")
 DEFINE_INT(regexp_tier_up_ticks, 1,

src/init/v8.cc

@@ -91,10 +91,9 @@ void V8::InitializeOncePerProcessImpl() {
   }
 
   if (FLAG_regexp_interpret_all && FLAG_regexp_tier_up) {
+    // Turning off the tier-up strategy, because the --regexp-interpret-all and
+    // --regexp-tier-up flags are incompatible.
     FLAG_regexp_tier_up = false;
-    PrintF(
-        "(WARNING) Turning off the tier-up strategy, because the "
-        "--regexp-interpret-all and --regexp-tier-up flags are incompatible.");
   }
 
   // The --jitless and --interpreted-frames-native-stack flags are incompatible