[codegen] Default to inlining off-heap builtin trampolines

Previously only AssemblerOptions created by AssemblerOptions::Default()
could have inline_offheap_trampolines set to true.

This fixes OutOfLineTruncateDoubleToI from generating calls via the
DoubleToI trampoline.

Bug: v8:9338
Change-Id: Ia4638cd185e9041c7c69996783d0ce5600e9723a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1662288Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62213}

src/codegen/assembler.cc

@@ -64,8 +64,8 @@ AssemblerOptions AssemblerOptions::Default(
   // might be run on real hardware.
   options.enable_simulator_code = !serializer;
 #endif
-  options.inline_offheap_trampolines =
-      FLAG_embedded_builtins && !serializer && !generating_embedded_builtin;
+  options.inline_offheap_trampolines &=
+      !serializer && !generating_embedded_builtin;
 #if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_ARM64
   const base::AddressRegion& code_range =
       isolate->heap()->memory_allocator()->code_range();

src/codegen/assembler.h

@@ -155,7 +155,7 @@ struct V8_EXPORT_PRIVATE AssemblerOptions {
   bool isolate_independent_code = false;
   // Enables the use of isolate-independent builtins through an off-heap
   // trampoline. (macro assembler feature).
-  bool inline_offheap_trampolines = false;
+  bool inline_offheap_trampolines = FLAG_embedded_builtins;
   // On some platforms, all code is within a given range in the process,
   // and the start of this range is configured here.
   Address code_range_start = 0;