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tcwang (Tiancong Wang)
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Dec 13 2018, 11:25 AM (126 w, 3 d)

Recent Activity

Apr 2 2020

tcwang added a comment to D67900: [libc++] Use builtin type traits whenever possible.

@zoecarver Thank you!

Apr 2 2020, 10:17 AM · Restricted Project

Apr 1 2020

tcwang added a comment to D67900: [libc++] Use builtin type traits whenever possible.

Thank you! Just let me know when the new patch is submitted.

Apr 1 2020, 4:21 PM · Restricted Project
tcwang added a comment to D67900: [libc++] Use builtin type traits whenever possible.

@tcwang here's you're reproducer: https://godbolt.org/z/RJtTBG

Thank you!

Apr 1 2020, 10:26 AM · Restricted Project

Mar 31 2020

tcwang added a comment to D67900: [libc++] Use builtin type traits whenever possible.

event.ii is the preprocessed test case that can be used to reproduce the error. I am trying to use c-reduce to reduce but due to many errors (25 in total), the reduced test case is actually having other errors. I will try to reduce it in the meantime. But just in case this can help the author to figure out the problem. Also attached the interestingness test in test.sh{F11652738}

Mar 31 2020, 4:33 PM · Restricted Project
tcwang added a comment to D67900: [libc++] Use builtin type traits whenever possible.

This patch has caused a regression on Chrome OS (https://bugs.chromium.org/p/chromium/issues/detail?id=1065276).

Mar 31 2020, 2:52 PM · Restricted Project

May 21 2019

tcwang added a comment to D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

The commit description of rLLD361190 does not contain Differential Revision: https://reviews.llvm.org/D61711, so the revision was not closed when you committed that...

Also, the description should probably say the two options are now exclusive:

(1) When both --symbol-ordering-file=<file> and --call-graph-order-file=<file> are present, whichever flag comes later will take precedence.

May 21 2019, 9:08 AM · Restricted Project, lld

May 20 2019

tcwang committed rGa5d8d01d6f2c: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile (authored by tcwang).
[ELF][Driver] Fix precedence of symbol ordering file and CGProfile
May 20 2019, 12:12 PM
tcwang committed rLLD361190: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
[ELF][Driver] Fix precedence of symbol ordering file and CGProfile
May 20 2019, 12:11 PM
tcwang committed rL361190: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
[ELF][Driver] Fix precedence of symbol ordering file and CGProfile
May 20 2019, 12:11 PM
tcwang committed rGaf4219adf5bf: Test commit, add an empty line. (authored by tcwang).
Test commit, add an empty line.
May 20 2019, 11:44 AM
tcwang committed rL361186: Test commit, add an empty line..
Test commit, add an empty line.
May 20 2019, 11:43 AM
tcwang committed rLLD361186: Test commit, add an empty line..
Test commit, add an empty line.
May 20 2019, 11:43 AM

May 16 2019

tcwang added inline comments to D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
May 16 2019, 8:03 PM · Restricted Project, lld
tcwang updated the diff for D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

Fix comments in options checking.

May 16 2019, 8:03 PM · Restricted Project, lld
tcwang added a comment to D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

Friendly ping on the patch.

May 16 2019, 3:13 PM · Restricted Project, lld

May 10 2019

tcwang added inline comments to D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
May 10 2019, 9:50 AM · Restricted Project, lld
tcwang updated the diff for D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

Fix comments on the unit test.

May 10 2019, 9:50 AM · Restricted Project, lld

May 9 2019

tcwang added a comment to D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

(1) When both --symbol-ordering-file=<file> and --call-graph-order-file=<file> are present, whichever flag comes later will take precedence.

It looks like this combination is a misuse of the feature. Instead of silently ignore a flag, I think we should report an error that these flags cannot be used together.

(2) When only --symbol-ordering-file=<file> is present, it takes precedence over implicit call graph (CGProfile) generated by CGProfilePass enabled in new pass manager.

This is fine by me.

May 9 2019, 10:53 AM · Restricted Project, lld
tcwang updated the diff for D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.

This patch is a fix for https://bugs.llvm.org/show_bug.cgi?id=41804.
We try to solve the precedence of user-specified symbol ordering file and C3 ordering provided as call graph. It deals with two case:
(1) When both --symbol-ordering-file=<file> and --call-graph-order-file=<file> are present, LLD reports an error and aborts.
(2) When only --symbol-ordering-file=<file> is present, it takes precedence over implicit call graph (CGProfile) generated by CGProfilePass enabled in new pass manager.

May 9 2019, 10:53 AM · Restricted Project, lld

May 8 2019

tcwang updated the summary of D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
May 8 2019, 6:20 PM · Restricted Project, lld
tcwang created D61711: [ELF][Driver] Fix precedence of symbol ordering file and CGProfile.
May 8 2019, 6:20 PM · Restricted Project, lld

Apr 9 2019

tcwang added inline comments to D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64.
Apr 9 2019, 11:31 AM · Restricted Project
tcwang updated the diff for D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64.

Fix some comments.

Apr 9 2019, 11:31 AM · Restricted Project
tcwang retitled D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64 from [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto. to [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64.
Apr 9 2019, 10:32 AM · Restricted Project
tcwang added a reviewer for D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64: peter.smith.
Apr 9 2019, 10:32 AM · Restricted Project
tcwang added reviewers for D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64: kristof.beyls, dlj, manojgupta.
Apr 9 2019, 10:31 AM · Restricted Project
tcwang created D60472: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto for ARM/AArch64.
Apr 9 2019, 10:31 AM · Restricted Project

Apr 8 2019

tcwang abandoned D60429: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto..
Apr 8 2019, 4:52 PM · Restricted Project, Restricted Project
tcwang created D60429: [AArch64][PowerPC][Driver] Allow setting crypto feature through -mcrypto..
Apr 8 2019, 4:51 PM · Restricted Project, Restricted Project

Mar 27 2019

tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments.

Mar 27 2019, 4:05 PM · Restricted Project
tcwang added inline comments to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 27 2019, 3:53 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments to filter out section-typed symbols, instead of empty named ones.

Mar 27 2019, 3:53 PM · Restricted Project

Mar 21 2019

tcwang added inline comments to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 21 2019, 3:28 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments

Mar 21 2019, 3:28 PM · Restricted Project
tcwang updated the summary of D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 21 2019, 2:17 PM · Restricted Project
tcwang added a comment to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Ping. I think I have addressed all the comments here. Please let me know if there are more concerns to address. Thanks!

Mar 21 2019, 9:06 AM · Restricted Project

Mar 14 2019

tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments

Mar 14 2019, 9:05 AM · Restricted Project
tcwang added inline comments to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 14 2019, 9:05 AM · Restricted Project

Mar 13 2019

tcwang added inline comments to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 13 2019, 4:24 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments

Mar 13 2019, 4:24 PM · Restricted Project
tcwang added a comment to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Thanks!

Mar 13 2019, 4:14 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fix comments. Add one more test to test the outputs of the flag can be used to
reproduce the order with --symbol-ordering-file

Mar 13 2019, 4:13 PM · Restricted Project
tcwang retitled D59311: [ELF] Dump symbols ordered by profiled guided section layout to file. from [ELF] Print symbols ordered by profiled guided section layout with verbose. to [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 13 2019, 3:59 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Update title.

Mar 13 2019, 3:59 PM · Restricted Project
tcwang added inline comments to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 13 2019, 3:56 PM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Add a flag to save the output. Also printing out the symbol names of the ordering, instead of
the section names.

Mar 13 2019, 3:56 PM · Restricted Project
tcwang added a comment to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Thanks again for the comments!

Mar 13 2019, 11:54 AM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Adding check against empty InputSection names, and don't print out empty names.

Mar 13 2019, 11:54 AM · Restricted Project
tcwang added a comment to D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Thank you so much for the comments! Do you care to elaborate more on the test? I am not sure what I should test? Thanks!

Mar 13 2019, 11:24 AM · Restricted Project
tcwang updated the diff for D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..

Fixing the comments.

Mar 13 2019, 11:24 AM · Restricted Project
tcwang created D59311: [ELF] Dump symbols ordered by profiled guided section layout to file..
Mar 13 2019, 10:43 AM · Restricted Project

Mar 8 2019

Herald added a project to D57386: [SelectionDAG] Codesize: don't expand SHIFT to SHIFT_PARTS: Restricted Project.

Hi, we recently found this revision breaks Linux kernel (https://bugs.chromium.org/p/chromium/issues/detail?id=938985). Please advise us how to solve it. Thanks!

Mar 8 2019, 10:58 AM · Restricted Project

Dec 14 2018

tcwang abandoned D55679: Place .text.hot section before .text..
Dec 14 2018, 1:51 PM
tcwang added a comment to D55679: Place .text.hot section before .text..
In D55679#1330672, @pcc wrote:

Thanks for the explanation.

It may seem like a trivial change now, but changes like this add up and may result in increased complexity later (e.g. suppose that we wanted to add an --output-section-ordering-file feature; this would need to interact somehow with this change), and once you start emulating another linker like this it can be difficult to undo the change since you don't know who might be unintentionally depending on the emulation. Unless there's evidence that more programs are relying on this assumption I think it's premature to code it into the linker.

I also consider it a bug for ChromeOS to make this assumption. This isn't the first lld transition issue we've seen whose root cause turned out to be an incorrect assumption. Can't you change ChromeOS so that instead of assuming that the first few pages are hot it just moves the pages covered by .text.hot into hugepages? It's possible to use a linker script to get the address of the start and end of .text.hot. See for example:
https://cs.chromium.org/chromium/src/base/android/library_loader/anchor_functions.lds
and how the symbols defined by that file are used.

Assuming that this is the code that implements hugepages:
https://cs.chromium.org/chromium/src/chromeos/hugepage_text/hugepage_text.cc
it would seem to result in simplifying the code a little as well.

Dec 14 2018, 1:51 PM

Dec 13 2018

tcwang added a comment to D55679: Place .text.hot section before .text..

Care to update the title of this review? ;)

Dec 13 2018, 4:32 PM
tcwang retitled D55679: Place .text.hot section before .text. from # Enter a commit message. # to Place .text.hot section before .text..
Dec 13 2018, 4:32 PM
tcwang added a reviewer for D55679: Place .text.hot section before .text.: gbiv.
Dec 13 2018, 3:31 PM
tcwang created D55679: Place .text.hot section before .text..
Dec 13 2018, 3:04 PM