[turbofan] Enable loop rotation

R=mstarzinger@chromium.org

Bug: v8:8423
Change-Id: Iefa50c221f38d1548ca2298e3c03c42d03d1c2d8
Reviewed-on: https://chromium-review.googlesource.com/c/1340281Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57582}

src/flag-definitions.h

@@ -495,7 +495,7 @@ DEFINE_BOOL(turbo_move_optimization, true, "optimize gap moves in TurboFan")
 DEFINE_BOOL(turbo_jt, true, "enable jump threading in TurboFan")
 DEFINE_BOOL(turbo_loop_peeling, true, "Turbofan loop peeling")
 DEFINE_BOOL(turbo_loop_variable, true, "Turbofan loop variable optimization")
-DEFINE_BOOL(turbo_loop_rotation, false, "Turbofan loop rotation")
+DEFINE_BOOL(turbo_loop_rotation, true, "Turbofan loop rotation")
 DEFINE_BOOL(turbo_cf_optimization, true, "optimize control flow in TurboFan")
 DEFINE_BOOL(turbo_escape, true, "enable escape analysis")
 DEFINE_BOOL(turbo_allocation_folding, true, "Turbofan allocation folding")