[csa] disable release build FixedArray bounds checks by default

Not unexpectedly, always emitting bounds checks regressed performance quite
a bit. This CL disables release builds bounds checks for now, until we found
and disabled the performance critical bounds checks.

Bug: v8:8029
Change-Id: Ifab95b2baf88adc5443765e8c132f80ed2bb4aad
Reviewed-on: https://chromium-review.googlesource.com/1170768
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55052}

src/code-stub-assembler.cc

@@ -1958,6 +1958,7 @@ void CodeStubAssembler::FixedArrayBoundsCheck(TNode<FixedArrayBase> array,
                                               Node* index,
                                               int additional_offset,
                                               ParameterMode parameter_mode) {
+  if (!FLAG_fixed_array_bounds_checks) return;
   DCHECK_EQ(0, additional_offset % kPointerSize);
   if (parameter_mode == ParameterMode::SMI_PARAMETERS) {
     TNode<Smi> effective_index;

src/flag-definitions.h

@@ -439,6 +439,8 @@ DEFINE_BOOL(trace_verify_csa, false, "trace code stubs verification")
 DEFINE_STRING(csa_trap_on_node, nullptr,
               "trigger break point when a node with given id is created in "
               "given stub. The format is: StubName,NodeId")
+DEFINE_BOOL_READONLY(fixed_array_bounds_checks, DEBUG_BOOL,
+                     "enable FixedArray bounds checks")
 DEFINE_BOOL(turbo_stats, false, "print TurboFan statistics")
 DEFINE_BOOL(turbo_stats_nvp, false,
             "print TurboFan statistics in machine-readable format")