r228234 - [modules] When using -E, we may try to merge decls despite having no Sema
Ben Langmuir
blangmuir at apple.com
Sat Mar 14 09:25:40 PDT 2015
Hi Richard,
This commit looks like it caused a regression in PCH-loading performance when the PCH imports modules. It doesn’t affect performance of loading modules on their own, or of a PCH that doesn’t use modules. If you have access to a Darwin system, it’s easy to reproduce with:
$ cat t.h
@import Cocoa;
$ cat t.m
// empty
$ clang -fmodules -fmodules-cache-path=mcp -x objective-c-header t.h -o t.pch
$ time clang -fmodules -fmodules-cache-path=mcp -Xclang -include-pch -Xclang t.pch t.m -fsyntax-only
I’m seeing ~8x difference between r228233 and r228234. In real world code (where the .m file isn’t empty) we’ve seen up to a ~90% difference.
Do you know what’s going on here? When a PCH loads I think we do it without Sema, but (at least previously) queued up the interesting Decls we saw for when Sema was added later. So I’m surprised this had such a big effect.
Ben
> On Feb 4, 2015, at 3:37 PM, Richard Smith <richard-llvm at metafoo.co.uk> wrote:
>
> Author: rsmith
> Date: Wed Feb 4 17:37:59 2015
> New Revision: 228234
>
> URL: http://llvm.org/viewvc/llvm-project?rev=228234&view=rev
> Log:
> [modules] When using -E, we may try to merge decls despite having no Sema
> object. In such a case, use the TU's DC for merging global decls rather than
> giving up when we find there is no TU scope.
>
> Ultimately, we should probably avoid all loading of decls when preprocessing,
> but there are other reasonable use cases for loading an AST file with no Sema
> object for which this is the right thing.
>
> Added:
> cfe/trunk/test/Modules/Inputs/preprocess/
> cfe/trunk/test/Modules/Inputs/preprocess/file.h
> cfe/trunk/test/Modules/Inputs/preprocess/fwd.h
> cfe/trunk/test/Modules/Inputs/preprocess/module.modulemap
> Modified:
> cfe/trunk/include/clang/Frontend/CompilerInstance.h
> cfe/trunk/lib/Frontend/CompilerInstance.cpp
> cfe/trunk/lib/Serialization/ASTReaderDecl.cpp
> cfe/trunk/test/Modules/preprocess.m
>
> Modified: cfe/trunk/include/clang/Frontend/CompilerInstance.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Frontend/CompilerInstance.h?rev=228234&r1=228233&r2=228234&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Frontend/CompilerInstance.h (original)
> +++ cfe/trunk/include/clang/Frontend/CompilerInstance.h Wed Feb 4 17:37:59 2015
> @@ -588,7 +588,7 @@ public:
> /// Create an external AST source to read a PCH file.
> ///
> /// \return - The new object on success, or null on failure.
> - static ExternalASTSource *createPCHExternalASTSource(
> + static IntrusiveRefCntPtr<ASTReader> createPCHExternalASTSource(
> StringRef Path, const std::string &Sysroot, bool DisablePCHValidation,
> bool AllowPCHWithCompilerErrors, Preprocessor &PP, ASTContext &Context,
> void *DeserializationListener, bool OwnDeserializationListener,
>
> Modified: cfe/trunk/lib/Frontend/CompilerInstance.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/CompilerInstance.cpp?rev=228234&r1=228233&r2=228234&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Frontend/CompilerInstance.cpp (original)
> +++ cfe/trunk/lib/Frontend/CompilerInstance.cpp Wed Feb 4 17:37:59 2015
> @@ -388,32 +388,30 @@ void CompilerInstance::createASTContext(
> void CompilerInstance::createPCHExternalASTSource(
> StringRef Path, bool DisablePCHValidation, bool AllowPCHWithCompilerErrors,
> void *DeserializationListener, bool OwnDeserializationListener) {
> - IntrusiveRefCntPtr<ExternalASTSource> Source;
> bool Preamble = getPreprocessorOpts().PrecompiledPreambleBytes.first != 0;
> - Source = createPCHExternalASTSource(
> + ModuleManager = createPCHExternalASTSource(
> Path, getHeaderSearchOpts().Sysroot, DisablePCHValidation,
> AllowPCHWithCompilerErrors, getPreprocessor(), getASTContext(),
> DeserializationListener, OwnDeserializationListener, Preamble,
> getFrontendOpts().UseGlobalModuleIndex);
> - ModuleManager = static_cast<ASTReader*>(Source.get());
> - getASTContext().setExternalSource(Source);
> }
>
> -ExternalASTSource *CompilerInstance::createPCHExternalASTSource(
> +IntrusiveRefCntPtr<ASTReader> CompilerInstance::createPCHExternalASTSource(
> StringRef Path, const std::string &Sysroot, bool DisablePCHValidation,
> bool AllowPCHWithCompilerErrors, Preprocessor &PP, ASTContext &Context,
> void *DeserializationListener, bool OwnDeserializationListener,
> bool Preamble, bool UseGlobalModuleIndex) {
> HeaderSearchOptions &HSOpts = PP.getHeaderSearchInfo().getHeaderSearchOpts();
>
> - std::unique_ptr<ASTReader> Reader;
> - Reader.reset(new ASTReader(PP, Context,
> - Sysroot.empty() ? "" : Sysroot.c_str(),
> - DisablePCHValidation,
> - AllowPCHWithCompilerErrors,
> - /*AllowConfigurationMismatch*/false,
> - HSOpts.ModulesValidateSystemHeaders,
> - UseGlobalModuleIndex));
> + IntrusiveRefCntPtr<ASTReader> Reader(
> + new ASTReader(PP, Context, Sysroot.empty() ? "" : Sysroot.c_str(),
> + DisablePCHValidation, AllowPCHWithCompilerErrors,
> + /*AllowConfigurationMismatch*/ false,
> + HSOpts.ModulesValidateSystemHeaders, UseGlobalModuleIndex));
> +
> + // We need the external source to be set up before we read the AST, because
> + // eagerly-deserialized declarations may use it.
> + Context.setExternalSource(Reader.get());
>
> Reader->setDeserializationListener(
> static_cast<ASTDeserializationListener *>(DeserializationListener),
> @@ -427,7 +425,7 @@ ExternalASTSource *CompilerInstance::cre
> // Set the predefines buffer as suggested by the PCH reader. Typically, the
> // predefines buffer will be empty.
> PP.setPredefines(Reader->getSuggestedPredefines());
> - return Reader.release();
> + return Reader;
>
> case ASTReader::Failure:
> // Unrecoverable failure: don't even try to process the input file.
> @@ -442,6 +440,7 @@ ExternalASTSource *CompilerInstance::cre
> break;
> }
>
> + Context.setExternalSource(nullptr);
> return nullptr;
> }
>
>
> Modified: cfe/trunk/lib/Serialization/ASTReaderDecl.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReaderDecl.cpp?rev=228234&r1=228233&r2=228234&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Serialization/ASTReaderDecl.cpp (original)
> +++ cfe/trunk/lib/Serialization/ASTReaderDecl.cpp Wed Feb 4 17:37:59 2015
> @@ -2591,6 +2591,11 @@ DeclContext *ASTDeclReader::getPrimaryCo
> return ED->getASTContext().getLangOpts().CPlusPlus? ED->getDefinition()
> : nullptr;
>
> + // We can see the TU here only if we have no Sema object. In that case,
> + // there's no TU scope to look in, so using the DC alone is sufficient.
> + if (auto *TU = dyn_cast<TranslationUnitDecl>(DC))
> + return TU;
> +
> return nullptr;
> }
>
>
> Added: cfe/trunk/test/Modules/Inputs/preprocess/file.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/preprocess/file.h?rev=228234&view=auto
> ==============================================================================
> --- cfe/trunk/test/Modules/Inputs/preprocess/file.h (added)
> +++ cfe/trunk/test/Modules/Inputs/preprocess/file.h Wed Feb 4 17:37:59 2015
> @@ -0,0 +1,3 @@
> +struct __FILE;
> +#include "fwd.h"
> +typedef struct __FILE FILE;
>
> Added: cfe/trunk/test/Modules/Inputs/preprocess/fwd.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/preprocess/fwd.h?rev=228234&view=auto
> ==============================================================================
> --- cfe/trunk/test/Modules/Inputs/preprocess/fwd.h (added)
> +++ cfe/trunk/test/Modules/Inputs/preprocess/fwd.h Wed Feb 4 17:37:59 2015
> @@ -0,0 +1 @@
> +struct __FILE;
>
> Added: cfe/trunk/test/Modules/Inputs/preprocess/module.modulemap
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/preprocess/module.modulemap?rev=228234&view=auto
> ==============================================================================
> --- cfe/trunk/test/Modules/Inputs/preprocess/module.modulemap (added)
> +++ cfe/trunk/test/Modules/Inputs/preprocess/module.modulemap Wed Feb 4 17:37:59 2015
> @@ -0,0 +1,2 @@
> +module fwd { header "fwd.h" export * }
> +module file { header "file.h" export * }
>
> Modified: cfe/trunk/test/Modules/preprocess.m
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/preprocess.m?rev=228234&r1=228233&r2=228234&view=diff
> ==============================================================================
> --- cfe/trunk/test/Modules/preprocess.m (original)
> +++ cfe/trunk/test/Modules/preprocess.m Wed Feb 4 17:37:59 2015
> @@ -1,9 +1,14 @@
> // RUN: rm -rf %t
> -// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -include %S/Inputs/preprocess-prefix.h -E %s | FileCheck -strict-whitespace %s
> -// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -x objective-c-header -emit-pch %S/Inputs/preprocess-prefix.h -o %t.pch
> -// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -include-pch %t.pch -E %s | FileCheck -strict-whitespace %s
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -include %S/Inputs/preprocess-prefix.h -E %s | FileCheck -strict-whitespace %s
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -x objective-c-header -emit-pch %S/Inputs/preprocess-prefix.h -o %t.pch
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -include-pch %t.pch -E %s | FileCheck -strict-whitespace %s
> +//
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -x objective-c++ -include %S/Inputs/preprocess-prefix.h -E %s | FileCheck -strict-whitespace %s
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -x objective-c++-header -emit-pch %S/Inputs/preprocess-prefix.h -o %t.pch
> +// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -I %S/Inputs/preprocess -x objective-c++ -include-pch %t.pch -E %s | FileCheck -strict-whitespace %s
> #import "diamond_right.h"
> #import "diamond_right.h" // to check that imports get their own line
> +#include "file.h"
> void test() {
> top_left_before();
> left_and_right();
> @@ -15,6 +20,7 @@ void test() {
>
> // CHECK: @import diamond_right; /* clang -E: implicit import for "{{.*}}diamond_right.h" */{{$}}
> // CHECK: @import diamond_right; /* clang -E: implicit import for "{{.*}}diamond_right.h" */{{$}}
> +// CHECK: @import file; /* clang -E: implicit import for "{{.*}}file.h" */{{$}}
> // CHECK-NEXT: void test() {{{$}}
> // CHECK-NEXT: top_left_before();{{$}}
> // CHECK-NEXT: left_and_right();{{$}}
>
>
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