Skip to content

Use memset in even more cases - #1273

Merged
Stephan T. Lavavej (StephanTLavavej) merged 17 commits into
microsoft:masterfrom
AdamBucior:fill_zero_optimization
Oct 29, 2020
Merged

Use memset in even more cases#1273
Stephan T. Lavavej (StephanTLavavej) merged 17 commits into
microsoft:masterfrom
AdamBucior:fill_zero_optimization

Conversation

@AdamBucior

@AdamBucior Adam Bucior (AdamBucior) commented Sep 5, 2020 •
edited
Loading

Copy link
Copy Markdown
Contributor

Another small PR to optimize (ranges::)(uninitialized_)fill(_n). I applied the optimization only to the _HAS_IF_CONSTEXPR branch because without if constexpr it becomes very tricky to implement and I don't know how long the !_HAS_IF_CONSTEXPR branch will live. Part of #431.

@AdamBucior
Adam Bucior (AdamBucior) requested a review from a team as a code owner September 5, 2020 10:56
@StephanTLavavej

Stephan T. Lavavej (StephanTLavavej) commented Sep 23, 2020

Copy link
Copy Markdown
Member

I pushed a merge to uninitialized_fill_n() in <memory> - it needed a bit of manual surgery, and I think I got it right, but please double-check.

@AdamBucior

Adam Bucior (AdamBucior) commented Sep 23, 2020

Copy link
Copy Markdown
Contributor Author

I pushed a merge to uninitialized_fill_n() in <memory> - it needed a bit of manual surgery, and I think I got it right, but please double-check.

Looks good

CaseyCarter
Casey Carter (CaseyCarter) reviewed Sep 24, 2020
View reviewed changes
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/xutility Outdated
Comment thread stl/inc/memory
Comment thread stl/inc/memory Outdated
Comment thread stl/inc/memory Outdated
Comment thread stl/inc/xmemory Outdated
Comment thread stl/inc/xmemory Outdated
Comment thread stl/inc/xutility Outdated
Comment thread stl/inc/xutility Outdated
@AdamBucior @CaseyCarter
static_assert is_scalar
4b0f4cd 
Co-authored-by: Casey Carter <cartec69@gmail.com>
AdamBucior
Adam Bucior (AdamBucior) commented Sep 24, 2020
View reviewed changes
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/algorithm Outdated
AdamBucior
Adam Bucior (AdamBucior) commented Sep 24, 2020
View reviewed changes
Comment thread stl/inc/algorithm Outdated
Comment thread stl/inc/algorithm Outdated
CaseyCarter
Casey Carter (CaseyCarter) approved these changes Oct 3, 2020
View reviewed changes

@CaseyCarter Casey Carter (CaseyCarter) left a comment •
edited
Loading

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM! Thanks for the extra test coverage.

@CaseyCarter Casey Carter (CaseyCarter) removed their assignment Oct 3, 2020
StephanTLavavej
Stephan T. Lavavej (StephanTLavavej) requested changes Oct 28, 2020
View reviewed changes

@StephanTLavavej Stephan T. Lavavej (StephanTLavavej) left a comment

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for implementing this optimization! I found one bug involving floating-point negative zero, but otherwise this looks very solid.

Comment thread tests/std/tests/VSO_0180469_fill_family/test.cpp Outdated
Comment thread stl/inc/memory
Comment thread stl/inc/xutility Outdated
Comment thread stl/inc/xutility Outdated
Comment thread stl/inc/xutility Outdated
Comment thread stl/inc/xutility Outdated
Comment thread tests/std/tests/P0674R1_make_shared_for_arrays/test.cpp
@AdamBucior @StephanTLavavej
Apply suggestions from code review
599542e 
Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
@AdamBucior
Code review
0048d22
@StephanTLavavej
Avoid Clang's -Wzero-as-null-pointer-constant warning.
3a937b3 
`static_cast<_Ty>(0)` emits this warning for object pointers, function
pointers, and `nullptr_t`. We can avoid this warning by using empty
braces to request zero-initialization.
@StephanTLavavej
Portably test for negative zero.
2866b64
@StephanTLavavej
Test allocate_shared<int[]>.
3d21ed4
@StephanTLavavej
Merge branch 'master' into gh1273_memset
d3fd586
@StephanTLavavej

Stephan T. Lavavej (StephanTLavavej) commented Oct 29, 2020

Copy link
Copy Markdown
Member

Looks great! I've pushed three small changes (FYI Casey Carter (@CaseyCarter)) and merged with master (without conflicts), so I can add your PR to today's batch for merging.

  • Avoid Clang's -Wzero-as-null-pointer-constant warning.
    • static_cast<_Ty>(0) emits this warning for object pointers, function pointers, and nullptr_t. We can avoid this warning by using empty braces to request zero-initialization.
  • Portably test for negative zero.
    • We conventionally avoid using internal machinery in tests unless it allows something to be tested that would be difficult otherwise. Instead of _Bit_cast, we can use <cmath>'s signbit() to detect negative zero.
  • Test allocate_shared<int[]>.

@StephanTLavavej
Stephan T. Lavavej (StephanTLavavej) merged commit a27d894 into microsoft:master Oct 29, 2020
@StephanTLavavej

Stephan T. Lavavej (StephanTLavavej) commented Oct 29, 2020

Copy link
Copy Markdown
Member

Thanks again for this optimization, automatically making user code faster! This will ship in VS 2019 16.9 Preview 2. 🎉

@AdamBucior
Adam Bucior (AdamBucior) deleted the fill_zero_optimization branch October 29, 2020 08:53
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@StephanTLavavej Stephan T. Lavavej (StephanTLavavej) StephanTLavavej approved these changes
+1 more reviewer
@CaseyCarter Casey Carter (CaseyCarter) CaseyCarter approved these changes
Reviewers whose approvals may not affect merge requirements

Assignees

@StephanTLavavej Stephan T. Lavavej (StephanTLavavej)

Labels

performance Must go faster

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

4 participants

@AdamBucior @StephanTLavavej @CaseyCarter @barcharcraz