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Bug 1533636 - Don't bother explicitly aligning when XDRing char16_t data: the operations we use to perform the little/native-endian conversion will correctly translate into, or translate out of, unaligned memory. r=tcampbell

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Differential Revision: https://phabricator.services.mozilla.com/D22654
This commit is contained in:
Jeff Walden
2019-03-06 13:36:47 -08:00
parent 27e56a5940
commit 36be0bb2c8
9 changed files with 300 additions and 150 deletions
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30
js/xpconnect/loader/ScriptPreloader.cpp
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@@ -60,15 +60,6 @@ using namespace mozilla::loader;
ProcessType ScriptPreloader::sProcessType;
// This type correspond to js::vm::XDRAlignment type, which is used as a size
// reference for alignment of XDR buffers.
using XDRAlign = uint16_t;
static const uint8_t sAlignPadding[sizeof(XDRAlign)] = {0, 0};
static inline size_t ComputeByteAlignment(size_t bytes, size_t align) {
return (align - (bytes % align)) % align;
}
nsresult ScriptPreloader::CollectReports(nsIHandleReportCallback* aHandleReport,
nsISupports* aData, bool aAnonymize) {
MOZ_COLLECT_REPORT(
@@ -540,8 +531,6 @@ Result<Ok, nsresult> ScriptPreloader::InitCacheInternal(
}
auto data = mCacheData.get<uint8_t>();
uint8_t* start = data.get();
MOZ_ASSERT(reinterpret_cast<uintptr_t>(start) % sizeof(XDRAlign) == 0);
auto end = data + size;
if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
@@ -566,10 +555,6 @@ Result<Ok, nsresult> ScriptPreloader::InitCacheInternal(
InputBuffer buf(header);
size_t len = data.get() - start;
size_t alignLen = ComputeByteAlignment(len, sizeof(XDRAlign));
data += alignLen;
size_t offset = 0;
while (!buf.finished()) {
auto script = MakeUnique<CachedScript>(*this, buf);
@@ -587,9 +572,6 @@ Result<Ok, nsresult> ScriptPreloader::InitCacheInternal(
}
offset += script->mSize;
MOZ_ASSERT(reinterpret_cast<uintptr_t>(scriptData.get()) %
sizeof(XDRAlign) ==
0);
script->mXDRRange.emplace(scriptData, scriptData + script->mSize);
// Don't pre-decode the script unless it was used in this process type
@@ -739,7 +721,6 @@ Result<Ok, nsresult> ScriptPreloader::WriteCache() {
OutputBuffer buf;
size_t offset = 0;
for (auto script : scripts) {
MOZ_ASSERT(offset % sizeof(XDRAlign) == 0);
script->mOffset = offset;
script->Code(buf);
@@ -749,22 +730,11 @@ Result<Ok, nsresult> ScriptPreloader::WriteCache() {
uint8_t headerSize[4];
LittleEndian::writeUint32(headerSize, buf.cursor());
size_t len = 0;
MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
len += sizeof(MAGIC);
MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
len += sizeof(headerSize);
MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
len += buf.cursor();
size_t alignLen = ComputeByteAlignment(len, sizeof(XDRAlign));
if (alignLen) {
MOZ_TRY(Write(fd, sAlignPadding, alignLen));
len += alignLen;
}
for (auto script : scripts) {
MOZ_ASSERT(script->mSize % sizeof(XDRAlign) == 0);
MOZ_TRY(Write(fd, script->Range().begin().get(), script->mSize));
len += script->mSize;
if (script->mScript) {
script->FreeData();