Author: Juan Manuel Martinez Caamaño Date: 2025-07-29T08:49:36+02:00 New Revision: 8b020d5434078145e2fd2b4f1a48bb1c78ace491
URL: https://github.com/llvm/llvm-project/commit/8b020d5434078145e2fd2b4f1a48bb1c78ace491 DIFF: https://github.com/llvm/llvm-project/commit/8b020d5434078145e2fd2b4f1a48bb1c78ace491.diff LOG: [Preprocessor] Do not expand macros if the input is already preprocessed (#137665) Preprocessing the preprocessor output again interacts poorly with some flag combinations when we perform a separate preprocessing stage. In our case, `-no-integrated-cpp -dD` triggered this issue; but I guess that other flags could also trigger problems (`-save-temps` instead of `-no-integrated-cpp`). Full context (which is quite weird I'll admit): * To cache OpenCL kernel compilation results, we use the `-no-integrated-cpp` for the driver to generate a separate preprocessing command (`clang -E`) before the rest of the compilation. * Some OpenCL C language features are implemented as macro definitions (in `opencl-c-base.h`). The semantic analysis queries the preprocessor to check if these are defined or not, for example, when we checks if a builtin is available when using `-fdeclare-opencl-builtins`. * To preserve these `#define` directives, on the preprocessor's output, we use `-dD`. However, other `#define` directives are also maintained besides OpenCL ones; which triggers the issue shown in this PR. A better fix for our particular case could have been to move the language features implemented as macros into some sort of a flag to be used together with `-fdeclare-opencl-builtins`. But I also thought that not preprocessing preprocessor outputs seemed like something desirable. I hope to work on this on a follow up. Added: clang/test/Preprocessor/preprocess-cpp-output.c clang/test/Preprocessor/preprocess-pragma-cpp-output.c Modified: clang/include/clang/Frontend/FrontendAction.h clang/include/clang/Lex/Preprocessor.h clang/lib/CodeGen/CodeGenAction.cpp clang/lib/Frontend/FrontendActions.cpp clang/lib/Frontend/Rewrite/FrontendActions.cpp Removed: ################################################################################ diff --git a/clang/include/clang/Frontend/FrontendAction.h b/clang/include/clang/Frontend/FrontendAction.h index 718684a67771a..08c5fbc78f8ae 100644 --- a/clang/include/clang/Frontend/FrontendAction.h +++ b/clang/include/clang/Frontend/FrontendAction.h @@ -84,6 +84,8 @@ class FrontendAction { /// \return True on success; on failure ExecutionAction() and /// EndSourceFileAction() will not be called. virtual bool BeginSourceFileAction(CompilerInstance &CI) { + if (CurrentInput.isPreprocessed()) + CI.getPreprocessor().SetMacroExpansionOnlyInDirectives(); return true; } @@ -98,7 +100,11 @@ class FrontendAction { /// /// This is guaranteed to only be called following a successful call to /// BeginSourceFileAction (and BeginSourceFile). - virtual void EndSourceFileAction() {} + virtual void EndSourceFileAction() { + if (CurrentInput.isPreprocessed()) + // Reset the preprocessor macro expansion to the default. + getCompilerInstance().getPreprocessor().SetEnableMacroExpansion(); + } /// Callback at the end of processing a single input, to determine /// if the output files should be erased or not. diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h index 4d82e20e5d4f3..71b0f8eab3bfa 100644 --- a/clang/include/clang/Lex/Preprocessor.h +++ b/clang/include/clang/Lex/Preprocessor.h @@ -1847,6 +1847,10 @@ class Preprocessor { MacroExpansionInDirectivesOverride = true; } + void SetEnableMacroExpansion() { + DisableMacroExpansion = MacroExpansionInDirectivesOverride = false; + } + /// Peeks ahead N tokens and returns that token without consuming any /// tokens. /// diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp index eb5b6045510df..2c0767f3d0af6 100644 --- a/clang/lib/CodeGen/CodeGenAction.cpp +++ b/clang/lib/CodeGen/CodeGenAction.cpp @@ -908,6 +908,8 @@ bool CodeGenAction::loadLinkModules(CompilerInstance &CI) { bool CodeGenAction::hasIRSupport() const { return true; } void CodeGenAction::EndSourceFileAction() { + ASTFrontendAction::EndSourceFileAction(); + // If the consumer creation failed, do nothing. if (!getCompilerInstance().hasASTConsumer()) return; @@ -932,7 +934,7 @@ CodeGenerator *CodeGenAction::getCodeGenerator() const { bool CodeGenAction::BeginSourceFileAction(CompilerInstance &CI) { if (CI.getFrontendOpts().GenReducedBMI) CI.getLangOpts().setCompilingModule(LangOptions::CMK_ModuleInterface); - return true; + return ASTFrontendAction::BeginSourceFileAction(CI); } static std::unique_ptr<raw_pwrite_stream> diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp index dcfbd5386f3dc..685a9bbf2cde9 100644 --- a/clang/lib/Frontend/FrontendActions.cpp +++ b/clang/lib/Frontend/FrontendActions.cpp @@ -181,7 +181,7 @@ bool GeneratePCHAction::shouldEraseOutputFiles() { bool GeneratePCHAction::BeginSourceFileAction(CompilerInstance &CI) { CI.getLangOpts().CompilingPCH = true; - return true; + return ASTFrontendAction::BeginSourceFileAction(CI); } std::vector<std::unique_ptr<ASTConsumer>> diff --git a/clang/lib/Frontend/Rewrite/FrontendActions.cpp b/clang/lib/Frontend/Rewrite/FrontendActions.cpp index 84e7a4f3f12d9..6c9c9d5b5c8d3 100644 --- a/clang/lib/Frontend/Rewrite/FrontendActions.cpp +++ b/clang/lib/Frontend/Rewrite/FrontendActions.cpp @@ -103,12 +103,13 @@ bool FixItAction::BeginSourceFileAction(CompilerInstance &CI) { } Rewriter.reset(new FixItRewriter(CI.getDiagnostics(), CI.getSourceManager(), CI.getLangOpts(), FixItOpts.get())); - return true; + return ASTFrontendAction::BeginSourceFileAction(CI); } void FixItAction::EndSourceFileAction() { // Otherwise rewrite all files. Rewriter->WriteFixedFiles(); + ASTFrontendAction::EndSourceFileAction(); } bool FixItRecompile::BeginInvocation(CompilerInstance &CI) { @@ -298,7 +299,7 @@ bool RewriteIncludesAction::BeginSourceFileAction(CompilerInstance &CI) { std::make_unique<RewriteImportsListener>(CI, OutputStream)); } - return true; + return PreprocessorFrontendAction::BeginSourceFileAction(CI); } void RewriteIncludesAction::ExecuteAction() { diff --git a/clang/test/Preprocessor/preprocess-cpp-output.c b/clang/test/Preprocessor/preprocess-cpp-output.c new file mode 100644 index 0000000000000..2c180601e30ac --- /dev/null +++ b/clang/test/Preprocessor/preprocess-cpp-output.c @@ -0,0 +1,10 @@ +// RUN: %clang_cc1 -E -x c %s | FileCheck %s --check-prefixes=EXPANDED +// RUN: %clang_cc1 -E -x cpp-output %s | FileCheck %s --check-prefixes=NOT-EXPANDED + +// EXPANDED: void __attribute__((__attribute__((always_inline)))) foo() +// NOT-EXPANDED: void __attribute__((always_inline)) foo() + +#define always_inline __attribute__((always_inline)) +void __attribute__((always_inline)) foo() { + return 4; +} diff --git a/clang/test/Preprocessor/preprocess-pragma-cpp-output.c b/clang/test/Preprocessor/preprocess-pragma-cpp-output.c new file mode 100644 index 0000000000000..d5389374c33c5 --- /dev/null +++ b/clang/test/Preprocessor/preprocess-pragma-cpp-output.c @@ -0,0 +1,21 @@ +// RUN: %clang_cc1 -E -x c %s | FileCheck %s +// RUN: %clang_cc1 -x c -fsyntax-only %s -verify +// RUN: %clang_cc1 -x cpp-output -fsyntax-only -verify %s +// expected-no-diagnostics + +// The preprocessor does not expand macro-identifiers in #pragma directives. +// When we preprocess & parse the code, clang expands the macros in directives. +// When we parse already preprocessed code, clang still has to expand the +// macros in the directives. +// This means that we're not always able to parse the preprocessor's output +// without preserving the definitions (-dD). + +#define FACTOR 4 + +void foo() { + // CHECK: #pragma unroll FACTOR + #pragma unroll FACTOR + for(;;) { + } + return; +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
