From fc0ddf551216761f5a9ecb07958fe92bbc8a9bc2 Mon Sep 17 00:00:00 2001 From: Anna Henningsen Date: Thu, 24 Jan 2019 12:00:14 +0100 Subject: [PATCH] [snapshot] Always align embedded blob code pointer and size Other platforms besides ARM64 Windows may also have alignment requirements, e.g. PPC and s390. These requirements may affect both the code pointer field and the size field, and so they each need alignment directives because they are stored in different sections. Since aligning wastes a handful of bytes at most, not making alignment conditional on the platform type seems like a good idea. Refs: https://github.com/nodejs/node/pull/24875 Change-Id: I1f58606af294be65e74a1f107cd05fc21e032704 Reviewed-on: https://chromium-review.googlesource.com/c/1433778 Commit-Queue: Jakob Gruber Reviewed-by: Jakob Gruber Cr-Commit-Position: refs/heads/master@{#59058} --- src/snapshot/embedded-file-writer.cc | 10 ++++------ src/snapshot/embedded-file-writer.h | 1 + 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/src/snapshot/embedded-file-writer.cc b/src/snapshot/embedded-file-writer.cc index 639428783477..4fc6ad18bb52 100644 --- a/src/snapshot/embedded-file-writer.cc +++ b/src/snapshot/embedded-file-writer.cc @@ -553,13 +553,11 @@ void PlatformDependentEmbeddedFileWriter::AlignToCodeAlignment() { } void PlatformDependentEmbeddedFileWriter::AlignToDataAlignment() { -#if defined(V8_OS_WIN) && defined(V8_TARGET_ARCH_ARM64) - // On Windows ARM64, instruction "ldr xt,[xn,v8_Default_embedded_blob_]" is - // generated by clang-cl to load elements in v8_Default_embedded_blob_. - // The generated instruction has scale 3 which requires the load target to be - // aligned at 8 bytes (2^3). + // On Windows ARM64, s390, PPC and possibly more platforms, aligned load + // instructions are used to retrieve v8_Default_embedded_blob_ and/or + // v8_Default_embedded_blob_size_. The generated instructions require the + // load target to be aligned at 8 bytes (2^3). fprintf(fp_, ".balign 8\n"); -#endif } void PlatformDependentEmbeddedFileWriter::Comment(const char* string) { diff --git a/src/snapshot/embedded-file-writer.h b/src/snapshot/embedded-file-writer.h index 55e134cd47f6..8323c4d53b78 100644 --- a/src/snapshot/embedded-file-writer.h +++ b/src/snapshot/embedded-file-writer.h @@ -286,6 +286,7 @@ class EmbeddedFileWriter : public EmbeddedFileWriterInterface { w->Comment("The size of the embedded blob in bytes."); w->SectionRoData(); + w->AlignToDataAlignment(); w->DeclareUint32(embedded_blob_size_symbol, blob->size()); w->Newline(); }