[arm64] Increase code alignment to 64

This should fix unexpected regressions which occur after builtins
modifications.

This CL affects alignment of embedded builtins on all configurations
and Code header size only for non-pointer compression configuration.

Bug: v8:11708
Change-Id: I8058197c5b768a699e7f52446424013e86203b57
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3700392
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81113}

src/common/globals.h

@@ -649,7 +649,7 @@ constexpr intptr_t kDoubleAlignmentMask = kDoubleAlignment - 1;
 // Desired alignment for generated code is 64 bytes on x64 (to allow 64-bytes
 // loop header alignment) and 32 bytes (to improve cache line utilization) on
 // other architectures.
-#if V8_TARGET_ARCH_X64
+#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_ARM64
 constexpr int kCodeAlignmentBits = 6;
 #elif V8_TARGET_ARCH_PPC64
 // 64 byte alignment is needed on ppc64 to make sure p10 prefixed instructions

src/objects/code.h

@@ -668,7 +668,7 @@ class Code : public HeapObject {
   // due to padding for code alignment.
 #if V8_TARGET_ARCH_ARM64
   static constexpr int kHeaderPaddingSize =
-      V8_EXTERNAL_CODE_SPACE_BOOL ? 4 : (COMPRESS_POINTERS_BOOL ? 8 : 20);
+      V8_EXTERNAL_CODE_SPACE_BOOL ? 4 : (COMPRESS_POINTERS_BOOL ? 8 : 52);
 #elif V8_TARGET_ARCH_MIPS64
   static constexpr int kHeaderPaddingSize = 20;
 #elif V8_TARGET_ARCH_LOONG64

src/snapshot/embedded/platform-embedded-file-writer-aix.cc

@@ -53,7 +53,7 @@ void PlatformEmbeddedFileWriterAIX::DeclareSymbolGlobal(const char* name) {
 }
 
 void PlatformEmbeddedFileWriterAIX::AlignToCodeAlignment() {
-#if V8_TARGET_ARCH_X64
+#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_ARM64
   // On x64 use 64-bytes code alignment to allow 64-bytes loop header alignment.
   static_assert((1 << 6) >= kCodeAlignment);
   fprintf(fp_, ".align 6\n");

src/snapshot/embedded/platform-embedded-file-writer-generic.cc

@@ -67,7 +67,7 @@ void PlatformEmbeddedFileWriterGeneric::AlignToCodeAlignment() {
   // On these architectures and platforms, we remap the builtins, so need these
   // to be aligned on a page boundary.
   fprintf(fp_, ".balign 4096\n");
-#elif V8_TARGET_ARCH_X64
+#elif V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_ARM64
   // On x64 use 64-bytes code alignment to allow 64-bytes loop header alignment.
   static_assert(64 >= kCodeAlignment);
   fprintf(fp_, ".balign 64\n");

src/snapshot/embedded/platform-embedded-file-writer-win.cc

@@ -609,7 +609,7 @@ void PlatformEmbeddedFileWriterWin::DeclareSymbolGlobal(const char* name) {
 }
 
 void PlatformEmbeddedFileWriterWin::AlignToCodeAlignment() {
-#if V8_TARGET_ARCH_X64
+#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_ARM64
   // On x64 use 64-bytes code alignment to allow 64-bytes loop header alignment.
   static_assert(64 >= kCodeAlignment);
   fprintf(fp_, ".balign 64\n");