[clang] [Clang] Handle C++20 export declarations in -dump-minimization-hints (PR #151666)
Ilya Biryukov via cfe-commits
cfe-commits at lists.llvm.org
Fri Aug 1 05:30:55 PDT 2025
https://github.com/ilya-biryukov updated https://github.com/llvm/llvm-project/pull/151666
>From d1c95d8babda9665310773acc66ead6ba5797649 Mon Sep 17 00:00:00 2001
From: Ilya Biryukov <ibiryukov at google.com>
Date: Fri, 1 Aug 2025 09:14:46 +0200
Subject: [PATCH 1/2] [Clang] Handle C++20 export declarations in
-dump-minimization-hints
Thanks to Justin Stitt for bringing this up, providing test cases and a
direction for the fix!
---
clang/lib/Frontend/FrontendAction.cpp | 82 ++++++++----
.../dump-minimization-hints-cpp20-modules.cpp | 117 ++++++++++++++++++
2 files changed, 172 insertions(+), 27 deletions(-)
create mode 100644 clang/test/Frontend/dump-minimization-hints-cpp20-modules.cpp
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 87cc2fc0cdd17..6c2f6f13a1fce 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -84,29 +84,28 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
if (!IsCollectingDecls)
return;
if (!D || isa<TranslationUnitDecl>(D) || isa<LinkageSpecDecl>(D) ||
- isa<NamespaceDecl>(D)) {
+ isa<NamespaceDecl>(D) || isa<ExportDecl>(D)) {
// These decls cover a lot of nested declarations that might not be used,
// reducing the granularity and making the output less useful.
return;
}
- auto *DC = D->getLexicalDeclContext();
- if (!DC || !DC->isFileContext()) {
- // We choose to work at namespace level to reduce complexity and the
- // number of cases we care about.
+ if (isa<ParmVarDecl>(D)) {
+ // Parameters are covered by their functions.
return;
}
+ auto *DC = D->getLexicalDeclContext();
+ if (!DC || !shouldIncludeDeclsIn(DC))
+ return;
PendingDecls.push_back(D);
- if (auto *NS = dyn_cast<NamespaceDecl>(DC)) {
- // Add any namespaces we have not seen before.
- // Note that we filter out namespaces from DeclRead as it includes too
- // all redeclarations and we only want the ones that had other used
- // declarations.
- while (NS && ProcessedNamespaces.insert(NS).second) {
- PendingDecls.push_back(NS);
-
- NS = dyn_cast<NamespaceDecl>(NS->getLexicalParent());
- }
+ for (; (isa<ExportDecl>(DC) || isa<NamespaceDecl>(DC)) &&
+ ProcessedDeclContexts.insert(DC).second;
+ DC = DC->getLexicalParent()) {
+ // Add any interesting decl contexts that we have not seen before.
+ // Note that we filter them out from DeclRead as that would include all
+ // redeclarations of namespaces, potentially those that do not have any
+ // imported declarations.
+ PendingDecls.push_back(cast<Decl>(DC));
}
}
@@ -205,12 +204,37 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
private:
std::vector<const Decl *> PendingDecls;
- llvm::SmallPtrSet<const NamespaceDecl *, 0> ProcessedNamespaces;
+ llvm::SmallPtrSet<const DeclContext *, 0> ProcessedDeclContexts;
bool IsCollectingDecls = true;
const SourceManager &SM;
std::unique_ptr<llvm::raw_ostream> OS;
+ static bool shouldIncludeDeclsIn(const DeclContext *DC) {
+ assert(DC && "DC is null");
+ // We choose to work at namespace level to reduce complexity and the number
+ // of cases we care about.
+ // We still need to carefully handle composite declarations like
+ // `ExportDecl`.
+ for (; DC; DC = DC->getLexicalParent()) {
+ if (DC->isFileContext())
+ return true;
+ if (isa<ExportDecl>(DC))
+ continue; // Depends on the parent.
+ return false;
+ }
+ llvm_unreachable("DeclConext chain must end with a translation unit");
+ }
llvm::SmallVector<CharSourceRange, 2> getRangesToMark(const Decl *D) {
+ if (auto *ED = dyn_cast<ExportDecl>(D)) {
+ if (!ED->hasBraces())
+ return {SM.getExpansionRange(ED->getExportLoc())};
+
+ return {SM.getExpansionRange(SourceRange(
+ ED->getExportLoc(),
+ lexForLBrace(ED->getExportLoc(), D->getLangOpts()))),
+ SM.getExpansionRange(ED->getRBraceLoc())};
+ }
+
auto *NS = dyn_cast<NamespaceDecl>(D);
if (!NS)
return {SM.getExpansionRange(D->getSourceRange())};
@@ -232,17 +256,7 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
}
}
}
- auto &LangOpts = D->getLangOpts();
- // Now skip one token, the next should be the lbrace.
- Token Tok;
- if (Lexer::getRawToken(TokenBeforeLBrace, Tok, SM, LangOpts, true) ||
- Lexer::getRawToken(Tok.getEndLoc(), Tok, SM, LangOpts, true) ||
- Tok.getKind() != tok::l_brace) {
- // On error or if we did not find the token we expected, avoid marking
- // everything inside the namespace as used.
- return {};
- }
- LBraceLoc = Tok.getLocation();
+ LBraceLoc = lexForLBrace(TokenBeforeLBrace, D->getLangOpts());
}
return {SM.getExpansionRange(SourceRange(NS->getBeginLoc(), LBraceLoc)),
SM.getExpansionRange(NS->getRBraceLoc())};
@@ -285,6 +299,20 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
OS->flush();
}
+
+ SourceLocation lexForLBrace(SourceLocation TokenBeforeLBrace,
+ const LangOptions &LangOpts) {
+ // Now skip one token, the next should be the lbrace.
+ Token Tok;
+ if (Lexer::getRawToken(TokenBeforeLBrace, Tok, SM, LangOpts, true) ||
+ Lexer::getRawToken(Tok.getEndLoc(), Tok, SM, LangOpts, true) ||
+ Tok.getKind() != tok::l_brace) {
+ // On error or if we did not find the token we expected, avoid marking
+ // everything inside the namespace as used.
+ return SourceLocation();
+ }
+ return Tok.getLocation();
+ }
};
/// Dumps deserialized declarations.
diff --git a/clang/test/Frontend/dump-minimization-hints-cpp20-modules.cpp b/clang/test/Frontend/dump-minimization-hints-cpp20-modules.cpp
new file mode 100644
index 0000000000000..d0750e0485b8a
--- /dev/null
+++ b/clang/test/Frontend/dump-minimization-hints-cpp20-modules.cpp
@@ -0,0 +1,117 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+// RUN: %clang_cc1 -std=c++20 %t/foo.cppm -emit-module-interface -o %t/foo.pcm
+// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %t/use.cpp -dump-minimization-hints=%t/decls
+// RUN: cat %t/decls
+// RUN: cat %t/decls | FileCheck -check-prefix=RANGE %s
+// RANGE:{
+// RANGE-NEXT:"required_ranges": [
+// RANGE-NEXT: {
+// RANGE-NEXT: "file": "{{.+}}/foo.cppm",
+// RANGE-NEXT: "range": [
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 3,
+// RANGE-NEXT: "column": 1
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 3,
+// RANGE-NEXT: "column": 22
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 4,
+// RANGE-NEXT: "column": 3
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 4,
+// RANGE-NEXT: "column": 9
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 4,
+// RANGE-NEXT: "column": 10
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 4,
+// RANGE-NEXT: "column": 43
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 6,
+// RANGE-NEXT: "column": 1
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 6,
+// RANGE-NEXT: "column": 2
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 8,
+// RANGE-NEXT: "column": 1
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 8,
+// RANGE-NEXT: "column": 7
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 8,
+// RANGE-NEXT: "column": 8
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 8,
+// RANGE-NEXT: "column": 25
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 9,
+// RANGE-NEXT: "column": 3
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 9,
+// RANGE-NEXT: "column": 36
+// RANGE-NEXT: }
+// RANGE-NEXT: },
+// RANGE-NEXT: {
+// RANGE-NEXT: "from": {
+// RANGE-NEXT: "line": 11,
+// RANGE-NEXT: "column": 1
+// RANGE-NEXT: },
+// RANGE-NEXT: "to": {
+// RANGE-NEXT: "line": 11,
+// RANGE-NEXT: "column": 2
+// RANGE-NEXT: }
+// RANGE-NEXT: }
+// RANGE-NEXT: ]
+// RANGE-NEXT: }
+// RANGE-NEXT:]
+// RANGE-NEXT:}
+
+//--- foo.cppm
+export module foo;
+
+namespace piecemeal { // line 3
+ export int used(int n) { return n + 1; }
+ export int unused(int n) { return n + 2; }
+}
+
+export namespace whole { // line 8
+ int used(int n) { return n + 1; }
+ int unused(int n) { return n + 3; }
+} // line 11
+
+//--- use.cpp
+import foo;
+
+int main() {
+ piecemeal::used(4); // only of the functions used from each namespace.
+ whole::used(4);
+}
>From bbf9c932e8443b62a23b66b21f03c40abcd9ff9c Mon Sep 17 00:00:00 2001
From: Ilya Biryukov <ibiryukov at google.com>
Date: Fri, 1 Aug 2025 14:30:14 +0200
Subject: [PATCH 2/2] Fix a typo, add a newline between functions
---
clang/lib/Frontend/FrontendAction.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 6c2f6f13a1fce..e913f49c34803 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -222,8 +222,9 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
continue; // Depends on the parent.
return false;
}
- llvm_unreachable("DeclConext chain must end with a translation unit");
+ llvm_unreachable("DeclContext chain must end with a translation unit");
}
+
llvm::SmallVector<CharSourceRange, 2> getRangesToMark(const Decl *D) {
if (auto *ED = dyn_cast<ExportDecl>(D)) {
if (!ED->hasBraces())
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