[builtins] Move builtin constants into read_only_space

Create a new function NewHeapNumberForCodeAssembler used only by
CodeAssembler that allocates in read_only_space whenever it is writable
(e.g. when constructing builtins). This can allocate in old_space for
CSA tests that run after read_only_space is sealed.

This move 512 bytes from old_space to read_only_space.

Bug: v8:7464
Change-Id: I3e29b38a8c062fa74feed63ecf0d07625c04347f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1752855
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63220}

src/compiler/code-assembler.cc

@@ -259,7 +259,7 @@ TNode<Number> CodeAssembler::NumberConstant(double value) {
     // (see AllocateAndInstallRequestedHeapObjects) since that makes it easier
     // to generate constant lookups for embedded builtins.
     return UncheckedCast<Number>(HeapConstant(
-        isolate()->factory()->NewHeapNumber(value, AllocationType::kOld)));
+        isolate()->factory()->NewHeapNumberForCodeAssembler(value)));
   }
 }
 

src/heap/factory.cc

@@ -2226,6 +2226,12 @@ Handle<HeapNumber> Factory::NewHeapNumber(AllocationType allocation) {
   return handle(HeapNumber::cast(result), isolate());
 }
 
+Handle<HeapNumber> Factory::NewHeapNumberForCodeAssembler(double value) {
+  return NewHeapNumber(value, isolate()->heap()->CanAllocateInReadOnlySpace()
+                                  ? AllocationType::kReadOnly
+                                  : AllocationType::kOld);
+}
+
 Handle<MutableHeapNumber> Factory::NewMutableHeapNumber(
     AllocationType allocation) {
   STATIC_ASSERT(HeapNumber::kSize <= kMaxRegularHeapObjectSize);

src/heap/factory.h

@@ -587,6 +587,10 @@ class V8_EXPORT_PRIVATE Factory {
   Handle<HeapNumber> NewHeapNumber(
       AllocationType allocation = AllocationType::kYoung);
 
+  // Creates a new HeapNumber in read-only space if possible otherwise old
+  // space.
+  Handle<HeapNumber> NewHeapNumberForCodeAssembler(double value);
+
   Handle<MutableHeapNumber> NewMutableHeapNumber(
       AllocationType allocation = AllocationType::kYoung);
   inline Handle<MutableHeapNumber> NewMutableHeapNumber(