[scudo] Minor code generation improvement
Summary:
It looks like clang was generating somewhat weird assembly with the current
code. `FromPrimary`, even though `const`, was replaced every time with the code
generated for `size <= SizeClassMap::kMaxSize` instead of using a variable or
register, and `FromPrimary` didn't induce `ClassId != 0` for the compiler, so a
dead branch was generated for `getActuallyAllocatedSize(Ptr, ClassId)` since
it's never called for `ClassId = 0` (Secondary backed allocations) [this one
was more wishful thinking on my side than anything else].
I rearranged the code bit so that the generated assembly is less clunky.
Also changed 2 whitespace inconsistencies that were bothering me.
Reviewers: alekseyshl, flowerhack
Reviewed By: flowerhack
Subscribers: llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D40976
llvm-svn: 320160
diff --git a/compiler-rt/lib/scudo/scudo_allocator.cpp b/compiler-rt/lib/scudo/scudo_allocator.cpp
index 4f2243e..6383c68 100644
--- a/compiler-rt/lib/scudo/scudo_allocator.cpp
+++ b/compiler-rt/lib/scudo/scudo_allocator.cpp
@@ -370,18 +370,15 @@
return FailureHandler::OnBadRequest();
if (CheckRssLimit && UNLIKELY(isRssLimitExceeded()))
- return FailureHandler::OnOOM();
+ return FailureHandler::OnOOM();
// Primary and Secondary backed allocations have a different treatment. We
// deal with alignment requirements of Primary serviced allocations here,
// but the Secondary will take care of its own alignment needs.
- const bool FromPrimary =
- PrimaryAllocator::CanAllocate(AlignedSize, MinAlignment);
-
void *Ptr;
u8 ClassId;
uptr AllocSize;
- if (FromPrimary) {
+ if (PrimaryAllocator::CanAllocate(AlignedSize, MinAlignment)) {
AllocSize = AlignedSize;
ClassId = SizeClassMap::ClassID(AllocSize);
ScudoTSD *TSD = getTSDAndLock();
@@ -396,7 +393,7 @@
return FailureHandler::OnOOM();
// If requested, we will zero out the entire contents of the returned chunk.
- if ((ForceZeroContents || ZeroContents) && FromPrimary)
+ if ((ForceZeroContents || ZeroContents) && ClassId)
memset(Ptr, 0, BackendAllocator.getActuallyAllocatedSize(Ptr, ClassId));
UnpackedHeader Header = {};
@@ -406,23 +403,23 @@
// Since the Secondary takes care of alignment, a non-aligned pointer
// means it is from the Primary. It is also the only case where the offset
// field of the header would be non-zero.
- CHECK(FromPrimary);
+ CHECK(ClassId);
UserBeg = RoundUpTo(UserBeg, Alignment);
uptr Offset = UserBeg - AlignedChunkHeaderSize - BackendPtr;
Header.Offset = Offset >> MinAlignmentLog;
}
CHECK_LE(UserBeg + Size, BackendPtr + AllocSize);
- Header.ClassId = ClassId;
Header.State = ChunkAllocated;
Header.AllocType = Type;
- if (FromPrimary) {
+ if (ClassId) {
+ Header.ClassId = ClassId;
Header.SizeOrUnusedBytes = Size;
} else {
// The secondary fits the allocations to a page, so the amount of unused
// bytes is the difference between the end of the user allocation and the
// next page boundary.
- uptr PageSize = GetPageSizeCached();
- uptr TrailingBytes = (UserBeg + Size) & (PageSize - 1);
+ const uptr PageSize = GetPageSizeCached();
+ const uptr TrailingBytes = (UserBeg + Size) & (PageSize - 1);
if (TrailingBytes)
Header.SizeOrUnusedBytes = PageSize - TrailingBytes;
}
diff --git a/compiler-rt/lib/scudo/scudo_utils.h b/compiler-rt/lib/scudo/scudo_utils.h
index 320eced..43448e0 100644
--- a/compiler-rt/lib/scudo/scudo_utils.h
+++ b/compiler-rt/lib/scudo/scudo_utils.h
@@ -31,6 +31,7 @@
void NORETURN dieWithMessage(const char *Format, ...);
bool hasHardwareCRC32();
+
} // namespace __scudo
#endif // SCUDO_UTILS_H_