[PATCH] D71913: [LTO/WPD] Enable aggressive WPD under LTO option

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson marked 5 inline comments as done.
tejohnson added inline comments.


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Comment at: clang/test/CodeGenCXX/lto-visibility-inference.cpp:73
   c1->f();
-  // ITANIUM-NOT: type.test{{.*}}!"_ZTS2C2"
+  // ITANIUM: type.test{{.*}}!"_ZTS2C2"
   // MS: type.test{{.*}}!"?AUC2@@"
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evgeny777 wrote:
> tejohnson wrote:
> > evgeny777 wrote:
> > > What caused this and other changes in this file?
> > Because we now will insert type tests for non-hidden vtables. This is enabled by the changes to LTO to interpret these based on the vcall_visibility metadata.
> The results of this test case
> ```
> %clang_cc1 -flto -triple x86_64-pc-windows-msvc -std=c++11 -fms-extensions -fwhole-program-vtables -flto-visibility-public-std -emit-llvm -o - %s | FileCheck --check-prefix=MS --check-prefix=MS-NOSTD %s
> ```
> look not correct to me. I think you shouldn't generate type tests for standard library classes with  `-flto-visibility-public-std`. Currently if this flag is given, clang doesn't do this either even with `-fvisibility=hidden`
The associated vtables would get the vcall_visibility public metadata, so the type tests themselves aren't problematic. I tend to think that an application using such options should simply stick with -fvisibility=hidden to get WPD and not use the new LTO option to convert all public vcall_visibility metadata to hidden.


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Comment at: clang/test/CodeGenCXX/thinlto-distributed-type-metadata.cpp:7
+// as expected.
+// RUN: %clang_cc1 -flto=thin -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fwhole-program-vtables -emit-llvm-bc -o %t.o %s
+// RUN: llvm-dis %t.o -o - | FileCheck --check-prefix=TT %s
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evgeny777 wrote:
> I think, we no longer need `-fvisibility hidden` here, do we?
Right, we aren't relying on the visibility for this test which is just ensuring the type tests are lowered properly in the distributed backends. I removed it.


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Comment at: llvm/lib/LTO/ThinLTOCodeGenerator.cpp:976
+  // via the internal option. Must be done before WPD below.
+  updateVCallVisibilityInIndex(*Index);
+
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evgeny777 wrote:
> evgeny777 wrote:
> > ditto
> updateVCallVisibilityInIndex(*Index, /* WholeProgramVisibilityEnabledInLTO */ false) ?
Missed this one before (did the InModule version but not InIndex), fixed.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71913/new/

https://reviews.llvm.org/D71913