[C++20] [Modules] Remove hardcoded path to imported module in BMIs

Close #62707

As we discussed before, we'll forbid the use of implicit generated path
for C++20 modules. And as I mentioned in
#62707, we've emitted a
warning for clang17 and we'll make it a hard error in clang18. And the
patch addresses the decision.

clang/docs/ReleaseNotes.rst

@@ -74,6 +74,10 @@ C/C++ Language Potentially Breaking Changes
   outlined in "The Equality Operator You Are Looking For" (`P2468 <http://wg21.link/p2468r2>`_).
   Fixes (`#68901: <https://github.com/llvm/llvm-project/issues/68901>`_).
 
+- Remove the hardcoded path to the imported modules for C++20 named modules. Now we
+  require all the dependent modules to specified from the command line.
+  See (`#62707: <https://github.com/llvm/llvm-project/issues/62707>`_).
+
 C++ Specific Potentially Breaking Changes
 -----------------------------------------
 - The name mangling rules for function templates has been changed to take into

clang/include/clang/Basic/DiagnosticSerializationKinds.td

@@ -129,10 +129,8 @@ def warn_module_system_bit_conflict : Warning<
   "as a non-system module; any difference in diagnostic options will be ignored">,
   InGroup<ModuleConflict>;
 
-def warn_reading_std_cxx_module_by_implicit_paths : Warning<
-  "it is deprecated to read module '%0' implicitly; it is going to be removed in clang 18; "
-  "consider to specify the dependencies explicitly">,
-  InGroup<DiagGroup<"read-modules-implicitly">>;
+def err_failed_to_find_module_file : Error<
+  "failed to find module file for module '%0'">;
 } // let CategoryName
 
 let CategoryName = "AST Serialization Issue" in {

clang/lib/Serialization/ASTReader.cpp

@@ -3037,12 +3037,17 @@ ASTReader::ReadControlBlock(ModuleFile &F,
         // location info are setup, in ReadAST.
         SourceLocation ImportLoc =
             ReadUntranslatedSourceLocation(Record[Idx++]);
-        off_t StoredSize = (off_t)Record[Idx++];
-        time_t StoredModTime = (time_t)Record[Idx++];
-        auto FirstSignatureByte = Record.begin() + Idx;
-        ASTFileSignature StoredSignature = ASTFileSignature::create(
-            FirstSignatureByte, FirstSignatureByte + ASTFileSignature::size);
-        Idx += ASTFileSignature::size;
+        off_t StoredSize = !IsImportingStdCXXModule ? (off_t)Record[Idx++] : 0;
+        time_t StoredModTime =
+            !IsImportingStdCXXModule ? (time_t)Record[Idx++] : 0;
+
+        ASTFileSignature StoredSignature;
+        if (!IsImportingStdCXXModule) {
+          auto FirstSignatureByte = Record.begin() + Idx;
+          StoredSignature = ASTFileSignature::create(
+              FirstSignatureByte, FirstSignatureByte + ASTFileSignature::size);
+          Idx += ASTFileSignature::size;
+        }
 
         std::string ImportedName = ReadString(Record, Idx);
         std::string ImportedFile;
@@ -3057,18 +3062,19 @@ ASTReader::ReadControlBlock(ModuleFile &F,
           ImportedFile = PP.getHeaderSearchInfo().getPrebuiltModuleFileName(
               ImportedName, /*FileMapOnly*/ !IsImportingStdCXXModule);
 
-        if (ImportedFile.empty()) {
-          // It is deprecated for C++20 Named modules to use the implicitly
-          // paths.
-          if (IsImportingStdCXXModule)
-            Diag(clang::diag::warn_reading_std_cxx_module_by_implicit_paths)
-                << ImportedName;
-
-          // Use BaseDirectoryAsWritten to ensure we use the same path in the
-          // ModuleCache as when writing.
-          ImportedFile = ReadPath(BaseDirectoryAsWritten, Record, Idx);
-        } else
-          SkipPath(Record, Idx);
+        // For C++20 Modules, we won't record the path to the imported modules
+        // in the BMI
+        if (!IsImportingStdCXXModule) {
+          if (ImportedFile.empty()) {
+            // Use BaseDirectoryAsWritten to ensure we use the same path in the
+            // ModuleCache as when writing.
+            ImportedFile = ReadPath(BaseDirectoryAsWritten, Record, Idx);
+          } else
+            SkipPath(Record, Idx);
+        } else if (ImportedFile.empty()) {
+          Diag(clang::diag::err_failed_to_find_module_file) << ImportedName;
+          return Missing;
+        }
 
         // If our client can't cope with us being out of date, we can't cope with
         // our dependency being missing.
@@ -5584,8 +5590,23 @@ bool ASTReader::readASTFileControlBlock(
       while (Idx < N) {
         // Read information about the AST file.
 
-        // Kind, StandardCXXModule, ImportLoc, Size, ModTime, Signature
-        Idx += 1 + 1 + 1 + 1 + 1 + ASTFileSignature::size;
+        // Skip Kind
+        Idx++;
+        bool IsStandardCXXModule = Record[Idx++];
+
+        // Skip ImportLoc
+        Idx++;
+
+        // In C++20 Modules, we don't record the path to imported
+        // modules in the BMI files.
+        if (IsStandardCXXModule) {
+          std::string ModuleName = ReadString(Record, Idx);
+          Listener.visitImport(ModuleName, /*Filename=*/"");
+          continue;
+        }
+
+        // Skip Size, ModTime and Signature
+        Idx += 1 + 1 + ASTFileSignature::size;
         std::string ModuleName = ReadString(Record, Idx);
         std::string Filename = ReadString(Record, Idx);
         ResolveImportedPath(Filename, ModuleDir);

clang/lib/Serialization/ASTWriter.cpp

@@ -1411,15 +1411,20 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
       Record.push_back(M.StandardCXXModule);
       AddSourceLocation(M.ImportLoc, Record);
 
-      // If we have calculated signature, there is no need to store
-      // the size or timestamp.
-      Record.push_back(M.Signature ? 0 : M.File.getSize());
-      Record.push_back(M.Signature ? 0 : getTimestampForOutput(M.File));
-
-      llvm::append_range(Record, M.Signature);
+      // We don't want to hard code the information about imported modules
+      // in the C++20 named modules.
+      if (!M.StandardCXXModule) {
+        // If we have calculated signature, there is no need to store
+        // the size or timestamp.
+        Record.push_back(M.Signature ? 0 : M.File.getSize());
+        Record.push_back(M.Signature ? 0 : getTimestampForOutput(M.File));
+        llvm::append_range(Record, M.Signature);
+      }
 
       AddString(M.ModuleName, Record);
-      AddPath(M.FileName, Record);
+
+      if (!M.StandardCXXModule)
+        AddPath(M.FileName, Record);
     }
     Stream.EmitRecord(IMPORTS, Record);
   }

clang/test/CodeGenCXX/module-initializer-guard-elision.cpp

@@ -8,34 +8,34 @@
 // RUN:  -o - | FileCheck %s --check-prefix=CHECK-O
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 P.cpp \
-// RUN:    -emit-module-interface -fmodule-file=O=O.pcm -o P.pcm
+// RUN:    -emit-module-interface -fprebuilt-module-path=%t -o P.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 P.pcm -S -emit-llvm \
-// RUN:  -o - | FileCheck %s --check-prefix=CHECK-P
+// RUN:   -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-P
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 Q.cpp \
 // RUN:    -emit-module-interface -o Q.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 Q.pcm -S -emit-llvm \
 // RUN:    -o - | FileCheck %s --check-prefix=CHECK-Q
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 R.cpp \
-// RUN:    -emit-module-interface -fmodule-file=Q=Q.pcm -o R.pcm
+// RUN:    -emit-module-interface -fprebuilt-module-path=%t -o R.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 R.pcm -S -emit-llvm \
-// RUN:    -o - | FileCheck %s --check-prefix=CHECK-R
+// RUN:    -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-R
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 S.cpp \
-// RUN:    -emit-module-interface -fmodule-file=Q=Q.pcm -fmodule-file=R=R.pcm -o S.pcm
+// RUN:    -emit-module-interface -fprebuilt-module-path=%t -o S.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 S.pcm -S -emit-llvm \
-// RUN:    -o - | FileCheck %s --check-prefix=CHECK-S
+// RUN:    -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-S
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 T.cpp \
-// RUN:    -emit-module-interface -fmodule-file=S=S.pcm -fmodule-file=R=R.pcm -o T.pcm
+// RUN:    -emit-module-interface -fprebuilt-module-path=%t -o T.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 T.pcm -S -emit-llvm \
-// RUN:    -o - | FileCheck %s --check-prefix=CHECK-T
+// RUN:    -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-T
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 U.cpp \
-// RUN:    -emit-module-interface -fmodule-file=T=T.pcm -fmodule-file=R=R.pcm -o U.pcm
+// RUN:    -emit-module-interface -fprebuilt-module-path=%t -o U.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 U.pcm -S -emit-llvm \
-// RUN:    -o - | FileCheck %s --check-prefix=CHECK-U
+// RUN:    -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-U
 
 // Testing cases where we can elide the module initializer guard variable.
 

clang/test/CodeGenCXX/module-intializer.cpp

@@ -12,37 +12,35 @@
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 O.pcm -S -emit-llvm \
 // RUN:  -o - | FileCheck %s --check-prefix=CHECK-O
 
-// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-part.cpp \
-// RUN:    -emit-module-interface -o M-part.pcm
-// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-part.pcm -S \
-// RUN: -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-P
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-Part.cpp \
+// RUN:    -emit-module-interface -o M-Part.pcm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-Part.pcm -S \
+// RUN:    -emit-module-interface  -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-P
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M.cpp \
-// RUN: -fmodule-file=N=N.pcm -fmodule-file=O=O.pcm -fmodule-file=M:Part=M-part.pcm \
-// RUN:    -emit-module-interface -o M.pcm
+// RUN:    -fprebuilt-module-path=%t -emit-module-interface -o M.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M.pcm -S -emit-llvm \
-// RUN:  -o - | FileCheck %s --check-prefix=CHECK-M
+// RUN:    -fprebuilt-module-path=%t -o - | FileCheck %s --check-prefix=CHECK-M
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 useM.cpp \
-// RUN: -fmodule-file=M=M.pcm -S -emit-llvm  -o - \
-// RUN: | FileCheck %s --check-prefix=CHECK-USE
+// RUN:   -fprebuilt-module-path=%t -S -emit-llvm  -o - \
+// RUN:   | FileCheck %s --check-prefix=CHECK-USE
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-impl.cpp \
-// RUN: -fmodule-file=M=M.pcm -S -emit-llvm  -o - \
-// RUN: | FileCheck %s --check-prefix=CHECK-IMPL
+// RUN:   -fprebuilt-module-path=%t -S -emit-llvm  -o - \
+// RUN:   | FileCheck %s --check-prefix=CHECK-IMPL
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 N.cpp -S -emit-llvm \
 // RUN:   -o - | FileCheck %s --check-prefix=CHECK-N
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 O.cpp -S -emit-llvm \
 // RUN:   -o - | FileCheck %s --check-prefix=CHECK-O
 
-// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-part.cpp -S -emit-llvm \
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M-Part.cpp -S -emit-llvm \
 // RUN:   -o - | FileCheck %s --check-prefix=CHECK-P
 
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 M.cpp \
-// RUN:   -fmodule-file=N.pcm -fmodule-file=O=O.pcm -fmodule-file=M:Part=M-part.pcm \
-// RUN:   -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-M
+// RUN:   -fprebuilt-module-path=%t -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-M
 
 //--- N-h.h
 
@@ -112,7 +110,7 @@ struct Croak {
 
 Croak Frog;
 
-//--- M-part.cpp
+//--- M-Part.cpp
 
 module;
 #include "P-h.h"

clang/test/CodeGenCXX/partitions.cpp

@@ -4,14 +4,14 @@
 
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface -triple %itanium_abi_triple %t/parta.cppm -o %t/mod-parta.pcm
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface -triple %itanium_abi_triple %t/partb.cppm -o %t/mod-partb.pcm
-// RUN: %clang_cc1 -std=c++20 -emit-module-interface -triple %itanium_abi_triple -fmodule-file=%t/mod-parta.pcm \
-// RUN:     -fmodule-file=%t/mod-partb.pcm %t/mod.cppm -o %t/mod.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface -triple %itanium_abi_triple %t/mod.cppm \
+// RUN:   -fprebuilt-module-path=%t -o %t/mod.pcm
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/mod.pcm -S -emit-llvm -disable-llvm-passes -o - \
-// RUN:     | FileCheck %t/mod.cppm
-// RUN: %clang_cc1 -std=c++20 -O2 -emit-module-interface -triple %itanium_abi_triple -fmodule-file=%t/mod-parta.pcm \
-// RUN:     -fmodule-file=%t/mod-partb.pcm %t/mod.cppm -o %t/mod.pcm
-// RUN: %clang_cc1 -std=c++20 -O2 -triple %itanium_abi_triple %t/mod.pcm -S -emit-llvm -disable-llvm-passes -o - \
-// RUN:     | FileCheck %t/mod.cppm  -check-prefix=CHECK-OPT
+// RUN:   -fprebuilt-module-path=%t | FileCheck %t/mod.cppm
+// RUN: %clang_cc1 -std=c++20 -O2 -emit-module-interface -triple %itanium_abi_triple \
+// RUN:   -fprebuilt-module-path=%t %t/mod.cppm -o %t/mod.pcm
+// RUN: %clang_cc1 -std=c++20 -O2 -triple %itanium_abi_triple %t/mod.pcm -S -emit-llvm \
+// RUN:   -fprebuilt-module-path=%t -disable-llvm-passes -o - | FileCheck %t/mod.cppm  -check-prefix=CHECK-OPT
 
 //--- parta.cppm
 export module mod:parta;

clang/test/Modules/cxx20-10-1-ex1.cpp

@@ -9,13 +9,15 @@
 // RUN:  -o %t/A_Internals.pcm
 
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex1-tu2.cpp \
-// RUN:  -fmodule-file=%t/A_Internals.pcm -o %t/A_Foo.pcm
+// RUN:  -fmodule-file=A:Internals=%t/A_Internals.pcm -o %t/A_Foo.pcm
 
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex1-tu3.cpp \
-// RUN:  -fmodule-file=%t/A_Foo.pcm -o %t/A.pcm
+// RUN:  -fmodule-file=A:Foo=%t/A_Foo.pcm -fmodule-file=A:Internals=%t/A_Internals.pcm \
+// RUN:  -o %t/A.pcm
 
 // RUN: %clang_cc1 -std=c++20 -emit-obj %t/std10-1-ex1-tu4.cpp \
-// RUN:  -fmodule-file=%t/A.pcm -o %t/ex1.o
+// RUN:  -fmodule-file=A=%t/A.pcm -fmodule-file=A:Foo=%t/A_Foo.pcm \
+// RUN:  -fmodule-file=A:Internals=%t/A_Internals.pcm -o %t/ex1.o
 
 // expected-no-diagnostics
 

clang/test/Modules/cxx20-importing-function-bodies.cppm

@@ -9,7 +9,8 @@
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/c.cppm \
 // RUN:     -emit-module-interface -fprebuilt-module-path=%t -o %t/c.pcm
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/c.pcm -S \
-// RUN:     -emit-llvm -disable-llvm-passes -o - | FileCheck %t/c.cppm
+// RUN:     -fprebuilt-module-path=%t -emit-llvm -disable-llvm-passes -o - \
+// RUN:     | FileCheck %t/c.cppm
 //
 // Be sure that we keep the same behavior as if optization not enabled.
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -O3 %t/a.cppm \
@@ -19,7 +20,8 @@
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -O3 %t/c.cppm \
 // RUN:     -emit-module-interface -fprebuilt-module-path=%t -o %t/c.pcm
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -O3 %t/c.pcm \
-// RUN:     -S -emit-llvm -disable-llvm-passes -o - | FileCheck %t/c.cppm
+// RUN:     -fprebuilt-module-path=%t -S -emit-llvm -disable-llvm-passes \
+// RUN:     -o - | FileCheck %t/c.cppm
 
 //--- a.cppm
 export module a;

clang/test/Modules/cxx20-module-file-info.cpp

@@ -14,13 +14,14 @@
 // RUN:  -o %t/B.pcm
 
 // RUN: %clang_cc1 -std=c++20 -module-file-info %t/B.pcm | FileCheck \
-// RUN:  --check-prefix=CHECK-B %s
+// RUN:     --check-prefix=CHECK-B %s
 
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/mod-info-tu3.cpp \
-// RUN:  -fmodule-file=%t/A.pcm -fmodule-file=%t/B.pcm -o %t/Foo.pcm
+// RUN:     -fmodule-file=A=%t/A.pcm -fmodule-file=B=%t/B.pcm -o %t/Foo.pcm
 
-// RUN: %clang_cc1 -std=c++20 -module-file-info %t/Foo.pcm | FileCheck \
-// RUN:  --check-prefix=CHECK-FOO %s
+// RUN: %clang_cc1 -std=c++20 -module-file-info %t/Foo.pcm -fmodule-file=A=%t/A.pcm \
+// RUN:     -fmodule-file=B=%t/B.pcm  | FileCheck \
+// RUN:     --check-prefix=CHECK-FOO %s
 
 // expected-no-diagnostics
 

clang/test/Modules/cxx20-partition-redeclarations.cpp

@@ -7,10 +7,10 @@
 // RUN: %clang_cc1 -std=c++20 A-interface.cpp -emit-module-interface \
 // RUN:   -fmodule-file=A-PubPart.pcm -o A.pcm
 
-// RUN: %clang_cc1 -std=c++20 A-impl-top.cpp -fsyntax-only -fmodule-file=A.pcm
-// RUN: %clang_cc1 -std=c++20 A-impl-part.cpp -fsyntax-only -fmodule-file=A.pcm
-// RUN: %clang_cc1 -std=c++20 A-impl-1.cpp -fsyntax-only -fmodule-file=A.pcm
-// RUN: %clang_cc1 -std=c++20 A-impl-2.cpp -fsyntax-only -fmodule-file=A.pcm
+// RUN: %clang_cc1 -std=c++20 A-impl-top.cpp -fsyntax-only -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 A-impl-part.cpp -fsyntax-only -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 A-impl-1.cpp -fsyntax-only -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 A-impl-2.cpp -fsyntax-only -fprebuilt-module-path=%t
 
 //--- A-interface.cpp
 export module A;

clang/test/Modules/eagerly-load-cxx-named-modules.cppm

@@ -7,8 +7,8 @@
 // RUN:    2>&1 | FileCheck %t/user.cpp
 // RUN: %clang_cc1 -std=c++20 %t/b.cppm -emit-module-interface -o %t/b.pcm \
 // RUN:    -fprebuilt-module-path=%t
-// RUN: %clang_cc1 -std=c++20 %t/b.pcm -Wno-read-modules-implicitly -S \
-// RUN:    -emit-llvm 2>&1 -o - | FileCheck %t/b.cppm
+// RUN: %clang_cc1 -std=c++20 %t/b.pcm -S \
+// RUN:    -fprebuilt-module-path=%t -emit-llvm 2>&1 -o - | FileCheck %t/b.cppm
 
 //--- a.cppm
 export module a;

clang/test/Modules/implicit-module-with-missing-path.cpp

@@ -6,7 +6,7 @@
 // RUN: echo -e "export module B;\nimport C;" >> %t/B.cppm
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/subdir/C.cppm -o %t/subdir/C.pcm
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface -fprebuilt-module-path=%t/subdir %t/B.cppm -o %t/B.pcm
-// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %s -fsyntax-only -verify -Wno-read-modules-implicitly
+// RUN: %clang_cc1 -std=c++20 -fmodule-file=B=%t/B.pcm %s -fsyntax-only -verify
 
-import B;
-import C; // expected-error {{module 'C' is needed but has not been provided, and implicit use of module files is disabled}}
+import B; // expected-error {{failed to find module file for module 'C'}}
+import C; // expected-error {{module 'C' not found}}

clang/test/Modules/module-init-duplicated-import.cppm

@@ -7,7 +7,7 @@
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/m.cppm \
 // RUN:      -emit-module-interface -fmodule-file=a=%t/a.pcm -o %t/m.pcm
 // RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/m.pcm  \
-// RUN:     -S -emit-llvm -o - | FileCheck %t/m.cppm
+// RUN:      -fmodule-file=a=%t/a.pcm -S -emit-llvm -o - | FileCheck %t/m.cppm
 
 //--- a.cppm
 export module a;

clang/test/Modules/no-duplicate-codegen-in-GMF.cppm

@@ -7,7 +7,8 @@
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/A.cppm -emit-module-interface -o %t/A.pcm
 // RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/B.cppm -emit-module-interface -o %t/B.pcm \
 // RUN:     -fprebuilt-module-path=%t
-// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/B.pcm -S -emit-llvm -o - | FileCheck %t/B.cppm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/B.pcm -S -emit-llvm -o - \
+// RUN:     -fprebuilt-module-path=%t | FileCheck %t/B.cppm
 
 //--- foo.h