[heap] adjust kMaxRegularHeapObjectSize on ppc64le

This is to address the first issue reported on v8:8453

Page::kPageSize is 524288
MemoryAllocator::GetCommitPageSize() returns 65536 on ppc

ObjectEndOffsetInCodePage() returns 458752
ObjectStartOffsetInCodePage() returns (65536 + 65536) => 131072

Therefore, memory = 327680, which is less than
kMaxRegularHeapObjectSize(507136), which causes the DCHECK to fail.

Bug: v8:8453
Change-Id: I6048192ded4234a6987371ec4d4b2a8553756c25
Reviewed-on: https://chromium-review.googlesource.com/c/1355422
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58001}

src/globals.h

@@ -241,7 +241,12 @@ constexpr int kExternalAllocationSoftLimit =
 // account.
 //
 // Current value: Page::kAllocatableMemory (on 32-bit arch) - 512 (slack).
+#ifdef V8_HOST_ARCH_PPC
+// Reduced kMaxRegularHeapObjectSize due to larger page size(64k) on ppc64le
+constexpr int kMaxRegularHeapObjectSize = 327680;
+#else
 constexpr int kMaxRegularHeapObjectSize = 507136;
+#endif
 
 constexpr int kBitsPerByte = 8;
 constexpr int kBitsPerByteLog2 = 3;

src/objects/hash-table.h

@@ -176,7 +176,12 @@ class HashTable : public HashTableBase {
   static const int kMinShrinkCapacity = 16;
 
   // Maximum length to create a regular HashTable (aka. non large object).
+#if V8_HOST_ARCH_PPC
+  // Reduced kMaxRegularCapacity due to reduced kMaxRegularHeapObjectSize
+  static const int kMaxRegularCapacity = 16384 / 2;
+#else
   static const int kMaxRegularCapacity = 16384;
+#endif
 
   // Returns the index for an entry (of the key)
   static constexpr inline int EntryToIndex(int entry) {

test/cctest/test-serialize.cc

@@ -1833,11 +1833,20 @@ TEST(CodeSerializerThreeBigStrings) {
   result_str = CompileRun("b")
                    ->ToString(CcTest::isolate()->GetCurrentContext())
                    .ToLocalChecked();
+#if V8_HOST_ARCH_PPC
+  CHECK(heap->InSpace(*v8::Utils::OpenHandle(*result_str), LO_SPACE));
+#else
   CHECK(heap->InSpace(*v8::Utils::OpenHandle(*result_str), OLD_SPACE));
+#endif
+
   result_str = CompileRun("c")
                    ->ToString(CcTest::isolate()->GetCurrentContext())
                    .ToLocalChecked();
+#if V8_HOST_ARCH_PPC
+  CHECK(heap->InSpace(*v8::Utils::OpenHandle(*result_str), LO_SPACE));
+#else
   CHECK(heap->InSpace(*v8::Utils::OpenHandle(*result_str), OLD_SPACE));
+#endif
 
   delete cache;
   source_a.Dispose();