[modules] Allow to validate system headers less often with `-fmodules-validate-once-per-build-session`.

[vsapsai]

Summary

Make flags -fmodules-validate-system-headers and
-fmodules-validate-once-per-build-session orthogonal, so they have
their own independent responsibilities - if system headers should be
validated and how often.

rdar://87988889

[vsapsai]

Here is the documentation for both flags:

• https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fmodules-validate-system-headers
• https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fmodules-validate-once-per-build-session

There is no mention of how these flags are interconnected.

[ributzka]

This makes sense. We shouldn't re-validate system headers when -fmodules-validate-once-per-build-session is passed too.

[ributzka]

LGTM

clang/lib/Serialization/ASTReader.cpp

case llvm::BitstreamEntry::EndBlock: {
       if (!DisableValidation && F.Kind != MK_ExplicitModule &&
           F.Kind != MK_PrebuiltModule) {
         bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
 
         // If we are reading a module, we will create a verification timestamp,
         // so we verify all input files.  Otherwise, verify only user input
         // files.
 
-        unsigned N = NumUserInputs;
-        if (ValidateSystemInputs ||
-            (HSOpts.ModulesValidateOncePerBuildSession &&
-             F.InputFilesValidationTimestamp <= HSOpts.BuildSessionTimestamp &&
-             F.Kind == MK_ImplicitModule))
-          N = NumInputs;
+        unsigned N = ValidateSystemInputs ? NumInputs : NumUserInputs;
+        if (HSOpts.ModulesValidateOncePerBuildSession &&
+            F.InputFilesValidationTimestamp > HSOpts.BuildSessionTimestamp &&
+            F.Kind == MK_ImplicitModule)
+          N = NumUserInputs;
 
         for (unsigned I = 0; I < N; ++I) {
           InputFile IF = getInputFile(F, I+1, Complain);
           if (!IF.getFile() || IF.isOutOfDate())
             return OutOfDate;
         }
       }
 

clang/test/Modules/fmodules-validate-once-per-build-session.c

 // RUN: echo 'void meow(void);' > %t/Inputs/foo.h
 // RUN: echo 'void woof(void);' > %t/Inputs/bar.h
 // RUN: echo 'module Foo { header "foo.h" }' > %t/Inputs/module.map
 // RUN: echo 'extern module Bar "bar.modulemap"' >> %t/Inputs/module.map
 // RUN: echo 'module Bar { header "bar.h" }' > %t/Inputs/bar.modulemap
 
 // ===
 // Compile the module.
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
 // RUN: ls -R %t/modules-cache | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache | grep Bar.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Bar.pcm.timestamp
 // RUN: cp %t/modules-cache/Foo.pcm %t/modules-to-compare/Foo-before.pcm
 // RUN: cp %t/modules-cache/Bar.pcm %t/modules-to-compare/Bar-before.pcm
 // RUN: cp %t/modules-cache-user/Foo.pcm %t/modules-to-compare/Foo-before-user.pcm
 // RUN: cp %t/modules-cache-user/Bar.pcm %t/modules-to-compare/Bar-before-user.pcm
 
 // ===
 // Use it, and make sure that we did not recompile it.
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
 // RUN: ls -R %t/modules-cache | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache | grep Bar.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Bar.pcm.timestamp
 // RUN: cp %t/modules-cache/Foo.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: cp %t/modules-cache/Bar.pcm %t/modules-to-compare/Bar-after.pcm
 // RUN: cp %t/modules-cache-user/Foo.pcm %t/modules-to-compare/Foo-after-user.pcm
 // RUN: cp %t/modules-cache-user/Bar.pcm %t/modules-to-compare/Bar-after-user.pcm
 
 // RUN: diff %t/modules-to-compare/Foo-before.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: diff %t/modules-to-compare/Bar-before.pcm %t/modules-to-compare/Bar-after.pcm
 // RUN: diff %t/modules-to-compare/Foo-before-user.pcm %t/modules-to-compare/Foo-after-user.pcm
 // RUN: diff %t/modules-to-compare/Bar-before-user.pcm %t/modules-to-compare/Bar-after-user.pcm
 
 // ===
 // Change the sources.
 // RUN: echo 'void meow2(void);' > %t/Inputs/foo.h
 // RUN: echo 'module Bar { header "bar.h" export * }' > %t/Inputs/bar.modulemap
 
 // ===
 // Use the module, and make sure that we did not recompile it if foo.h or
 // module.map are system files, even though the sources changed.
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache-user -fsyntax-only -I %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session %s
 // RUN: ls -R %t/modules-cache | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache | grep Bar.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache-user | grep Bar.pcm.timestamp
 // RUN: cp %t/modules-cache/Foo.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: cp %t/modules-cache/Bar.pcm %t/modules-to-compare/Bar-after.pcm
 // RUN: cp %t/modules-cache-user/Foo.pcm %t/modules-to-compare/Foo-after-user.pcm
 // RUN: cp %t/modules-cache-user/Bar.pcm %t/modules-to-compare/Bar-after-user.pcm
 
 // RUN: diff %t/modules-to-compare/Foo-before.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: diff %t/modules-to-compare/Bar-before.pcm %t/modules-to-compare/Bar-after.pcm
 // When foo.h is a user header, we will always validate it.
 // RUN: not diff %t/modules-to-compare/Foo-before-user.pcm %t/modules-to-compare/Foo-after-user.pcm
 // RUN: not diff %t/modules-to-compare/Bar-before-user.pcm %t/modules-to-compare/Bar-after-user.pcm
 
 // ===
 // Recompile the module if the today's date is before 01 January 2100.
-// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fbuild-session-timestamp=4102441200 -fmodules-validate-once-per-build-session %s
+// RUN: %clang_cc1 -cc1 -fmodules -fimplicit-module-maps -fdisable-module-hash -fmodules-cache-path=%t/modules-cache -fsyntax-only -isystem %t/Inputs -fmodules-validate-system-headers -fbuild-session-timestamp=4102441200 -fmodules-validate-once-per-build-session %s
 // RUN: ls -R %t/modules-cache | grep Foo.pcm.timestamp
 // RUN: ls -R %t/modules-cache | grep Bar.pcm.timestamp
 // RUN: cp %t/modules-cache/Foo.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: cp %t/modules-cache/Bar.pcm %t/modules-to-compare/Bar-after.pcm
 
 // RUN: not diff %t/modules-to-compare/Foo-before.pcm %t/modules-to-compare/Foo-after.pcm
 // RUN: not diff %t/modules-to-compare/Bar-before.pcm %t/modules-to-compare/Bar-after.pcm

clang/test/Modules/validate-system-headers.m

 
 // Modify the system header...
 // RUN: echo ' ' >> %t/Inputs/usr/include/foo.h
 
 // Don't recompile due to -fmodules-validate-once-per-build-session
 // RUN: %clang_cc1 -isystem %t/Inputs/usr/include -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/ModuleCache -fdisable-module-hash -x objective-c-header -fsyntax-only %s -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session
 // RUN: diff %t/ModuleCache/Foo.pcm %t/Foo.pcm.saved
 
-// Now add -fmodules-validate-system-headers and rebuild
+// Now add -fmodules-validate-system-headers and rebuild. No recompilation due to -fmodules-validate-once-per-build-session
 // RUN: %clang_cc1 -isystem %t/Inputs/usr/include -fmodules -fimplicit-module-maps -fmodules-validate-system-headers -fmodules-cache-path=%t/ModuleCache -fdisable-module-hash -x objective-c-header -fsyntax-only %s -fbuild-session-timestamp=1390000000 -fmodules-validate-once-per-build-session
-// RUN: not diff %t/ModuleCache/Foo.pcm %t/Foo.pcm.saved
+// RUN: diff %t/ModuleCache/Foo.pcm %t/Foo.pcm.saved
 
 @import Foo;