https://github.com/qiongsiwu created
https://github.com/llvm/llvm-project/pull/124786
When computing the context hash, `clang` always includes the compiler's working
directory. This can lead to situations when the only difference between two
compilations is the working directory, different module variants are generated.
These variants are redundant. This PR implements an optimization that ignores
the working directory when computing the context hash when safe.
Specifically, `clang` checks if it is safe to ignore the working directory in
`isSafeToIgnoreCWD`. The check involves going through compile command options
to see if any paths specified are relative. The definition of relative path
used here is that the input path is not empty, and
`llvm::sys::path::is_absolute` is false. If all the paths examined are not
relative, `clang` considers it safe to ignore the current working directory and
does not consider the working directory when computing the context hash.
>From 7060564de1bb6062639f4b4839fa17958f212755 Mon Sep 17 00:00:00 2001
From: Qiongsi Wu <qiongsi...@apple.com>
Date: Mon, 27 Jan 2025 16:44:30 -0800
Subject: [PATCH] Initial implementation of clang modules current working
directory pruning.
---
.../DependencyScanningService.h | 5 +-
.../DependencyScanning/ModuleDepCollector.cpp | 92 ++++++++++++-
.../ClangScanDeps/modules-context-hash-cwd.c | 123 ++++++++++++++++++
clang/test/ClangScanDeps/working-dir.m | 2 +-
clang/tools/clang-scan-deps/ClangScanDeps.cpp | 2 +
5 files changed, 219 insertions(+), 5 deletions(-)
create mode 100644 clang/test/ClangScanDeps/modules-context-hash-cwd.c
diff --git
a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
index 4a343f2872d8d9..9ad8e68c33eb10 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h
@@ -63,7 +63,10 @@ enum class ScanningOptimizations {
/// Canonicalize -D and -U options.
Macros = 8,
- DSS_LAST_BITMASK_ENUM(Macros),
+ /// Ignore the compiler's working directory if it is safe.
+ IgnoreCWD = 0x10,
+
+ DSS_LAST_BITMASK_ENUM(IgnoreCWD),
Default = All
};
diff --git a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
index 2e97cac0796cee..714efb86fa3796 100644
--- a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -397,9 +397,92 @@ void
ModuleDepCollector::applyDiscoveredDependencies(CompilerInvocation &CI) {
}
}
+static bool isSafeToIgnoreCWD(const CowCompilerInvocation &CI) {
+ // Check if the command line input uses relative paths.
+ // It is not safe to ignore the current working directory if any of the
+ // command line inputs use relative paths.
+#define IF_RELATIVE_RETURN_FALSE(PATH)
\
+ do {
\
+ if (!PATH.empty() && !llvm::sys::path::is_absolute(PATH))
\
+ return false;
\
+ } while (0)
+
+#define IF_ANY_RELATIVE_RETURN_FALSE(PATHS)
\
+ do {
\
+ if (std::any_of(PATHS.begin(), PATHS.end(), [](const auto &P) {
\
+ return !P.empty() && !llvm::sys::path::is_absolute(P);
\
+ }))
\
+ return false;
\
+ } while (0)
+
+ // Header search paths.
+ const auto &HeaderSearchOpts = CI.getHeaderSearchOpts();
+ IF_RELATIVE_RETURN_FALSE(HeaderSearchOpts.Sysroot);
+ for (auto &Entry : HeaderSearchOpts.UserEntries)
+ if (Entry.IgnoreSysRoot)
+ IF_RELATIVE_RETURN_FALSE(Entry.Path);
+ IF_RELATIVE_RETURN_FALSE(HeaderSearchOpts.ResourceDir);
+ IF_RELATIVE_RETURN_FALSE(HeaderSearchOpts.ModuleCachePath);
+ IF_RELATIVE_RETURN_FALSE(HeaderSearchOpts.ModuleUserBuildPath);
+ for (auto I = HeaderSearchOpts.PrebuiltModuleFiles.begin(),
+ E = HeaderSearchOpts.PrebuiltModuleFiles.end();
+ I != E;) {
+ auto Current = I++;
+ IF_RELATIVE_RETURN_FALSE(Current->second);
+ }
+ IF_ANY_RELATIVE_RETURN_FALSE(HeaderSearchOpts.PrebuiltModulePaths);
+ IF_ANY_RELATIVE_RETURN_FALSE(HeaderSearchOpts.VFSOverlayFiles);
+
+ // Preprocessor options.
+ const auto &PPOpts = CI.getPreprocessorOpts();
+ IF_ANY_RELATIVE_RETURN_FALSE(PPOpts.MacroIncludes);
+ IF_ANY_RELATIVE_RETURN_FALSE(PPOpts.Includes);
+ IF_RELATIVE_RETURN_FALSE(PPOpts.ImplicitPCHInclude);
+
+ // Frontend options.
+ const auto &FrontendOpts = CI.getFrontendOpts();
+ for (const FrontendInputFile &Input : FrontendOpts.Inputs) {
+ if (Input.isBuffer())
+ continue; // FIXME: Can this happen when parsing command-line?
+
+ IF_RELATIVE_RETURN_FALSE(Input.getFile());
+ }
+ IF_RELATIVE_RETURN_FALSE(FrontendOpts.CodeCompletionAt.FileName);
+ IF_ANY_RELATIVE_RETURN_FALSE(FrontendOpts.ModuleMapFiles);
+ IF_ANY_RELATIVE_RETURN_FALSE(FrontendOpts.ModuleFiles);
+ IF_ANY_RELATIVE_RETURN_FALSE(FrontendOpts.ModulesEmbedFiles);
+ IF_ANY_RELATIVE_RETURN_FALSE(FrontendOpts.ASTMergeFiles);
+ IF_RELATIVE_RETURN_FALSE(FrontendOpts.OverrideRecordLayoutsFile);
+ IF_RELATIVE_RETURN_FALSE(FrontendOpts.StatsFile);
+
+ // Filesystem options.
+ const auto &FileSystemOpts = CI.getFileSystemOpts();
+ IF_RELATIVE_RETURN_FALSE(FileSystemOpts.WorkingDir);
+
+ // Codegen options.
+ const auto &CodeGenOpts = CI.getCodeGenOpts();
+ IF_RELATIVE_RETURN_FALSE(CodeGenOpts.DebugCompilationDir);
+ IF_RELATIVE_RETURN_FALSE(CodeGenOpts.CoverageCompilationDir);
+
+ // Sanitizer options.
+ IF_ANY_RELATIVE_RETURN_FALSE(CI.getLangOpts().NoSanitizeFiles);
+
+ // Coverage mappings.
+ IF_RELATIVE_RETURN_FALSE(CodeGenOpts.ProfileInstrumentUsePath);
+ IF_RELATIVE_RETURN_FALSE(CodeGenOpts.SampleProfileFile);
+ IF_RELATIVE_RETURN_FALSE(CodeGenOpts.ProfileRemappingFile);
+
+ // Dependency output options.
+ for (auto &ExtraDep : CI.getDependencyOutputOpts().ExtraDeps)
+ IF_RELATIVE_RETURN_FALSE(ExtraDep.first);
+
+ return true;
+}
+
static std::string getModuleContextHash(const ModuleDeps &MD,
const CowCompilerInvocation &CI,
bool EagerLoadModules,
+ bool IgnoreCWD,
llvm::vfs::FileSystem &VFS) {
llvm::HashBuilder<llvm::TruncatedBLAKE3<16>, llvm::endianness::native>
HashBuilder;
@@ -410,7 +493,7 @@ static std::string getModuleContextHash(const ModuleDeps
&MD,
HashBuilder.add(getClangFullRepositoryVersion());
HashBuilder.add(serialization::VERSION_MAJOR, serialization::VERSION_MINOR);
llvm::ErrorOr<std::string> CWD = VFS.getCurrentWorkingDirectory();
- if (CWD)
+ if (CWD && !IgnoreCWD)
HashBuilder.add(*CWD);
// Hash the BuildInvocation without any input files.
@@ -443,8 +526,11 @@ static std::string getModuleContextHash(const ModuleDeps
&MD,
void ModuleDepCollector::associateWithContextHash(
const CowCompilerInvocation &CI, ModuleDeps &Deps) {
- Deps.ID.ContextHash = getModuleContextHash(
- Deps, CI, EagerLoadModules, ScanInstance.getVirtualFileSystem());
+ bool IgnoreCWD = any(OptimizeArgs & ScanningOptimizations::IgnoreCWD) &&
+ isSafeToIgnoreCWD(CI);
+ Deps.ID.ContextHash =
+ getModuleContextHash(Deps, CI, EagerLoadModules, IgnoreCWD,
+ ScanInstance.getVirtualFileSystem());
bool Inserted = ModuleDepsByID.insert({Deps.ID, &Deps}).second;
(void)Inserted;
assert(Inserted && "duplicate module mapping");
diff --git a/clang/test/ClangScanDeps/modules-context-hash-cwd.c
b/clang/test/ClangScanDeps/modules-context-hash-cwd.c
new file mode 100644
index 00000000000000..45be72301c635d
--- /dev/null
+++ b/clang/test/ClangScanDeps/modules-context-hash-cwd.c
@@ -0,0 +1,123 @@
+// Test current directory pruning when computing the context hash.
+
+// REQUIRES: shell
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb0.json.in > %t/cdb0.json
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb1.json.in > %t/cdb1.json
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb2.json.in > %t/cdb2.json
+// RUN: clang-scan-deps -compilation-database %t/cdb0.json -format
experimental-full > %t/result0.json
+// RUN: clang-scan-deps -compilation-database %t/cdb1.json -format
experimental-full > %t/result1.json
+// RUN: clang-scan-deps -compilation-database %t/cdb2.json -format
experimental-full
-optimize-args=header-search,system-warnings,vfs,canonicalize-macros >
%t/result2.json
+// RUN: cat %t/result0.json %t/result1.json | FileCheck %s
+// RUN: cat %t/result0.json %t/result2.json | FileCheck %s
-check-prefix=SKIPOPT
+
+//--- cdb0.json.in
+[{
+ "directory": "DIR",
+ "command": "clang -c DIR/tu.c -fmodules -fmodules-cache-path=DIR/cache
-IDIR/include/ -o DIR/tu.o",
+ "file": "DIR/tu.c"
+}]
+
+//--- cdb1.json.in
+[{
+ "directory": "DIR/a",
+ "command": "clang -c DIR/tu.c -fmodules -fmodules-cache-path=DIR/cache
-IDIR/include/ -o DIR/tu.o",
+ "file": "DIR/tu.c"
+}]
+
+//--- cdb2.json.in
+[{
+ "directory": "DIR/a/",
+ "command": "clang -c DIR/tu.c -fmodules -fmodules-cache-path=DIR/cache
-IDIR/include/ -o DIR/tu.o",
+ "file": "DIR/tu.c"
+}]
+
+//--- include/module.modulemap
+module mod {
+ header "mod.h"
+}
+
+//--- include/mod.h
+
+//--- tu.c
+#include "mod.h"
+
+// Check that result0 and result1 compute the same hash with optimization
+// on. The only difference between result0 and result1 is the compiler's
+// working directory.
+// CHECK: {
+// CHECK-NEXT: "modules": [
+// CHECK-NEXT: {
+// CHECK-NEXT: "clang-module-deps": [],
+// CHECK: "context-hash": "[[HASH:.*]]",
+// CHECK: }
+// CHECK: "translation-units": [
+// CHECK: {
+// CHECK: "commands": [
+// CHECK: {
+// CHECK-NEXT: "clang-context-hash": "{{.*}}",
+// CHECK-NEXT: "clang-module-deps": [
+// CHECK-NEXT: {
+// CHECK-NEXT: "context-hash": "[[HASH]]",
+// CHECK-NEXT: "module-name": "mod"
+// CHECK: }
+// CHECK: ],
+// CHECK: {
+// CHECK-NEXT: "modules": [
+// CHECK-NEXT: {
+// CHECK-NEXT: "clang-module-deps": [],
+// CHECK: "context-hash": "[[HASH]]",
+// CHECK: }
+// CHECK: "translation-units": [
+// CHECK: {
+// CHECK: "commands": [
+// CHECK: {
+// CHECK-NEXT: "clang-context-hash": "{{.*}}",
+// CHECK-NEXT: "clang-module-deps": [
+// CHECK-NEXT: {
+// CHECK-NEXT: "context-hash": "[[HASH]]",
+// CHECK-NEXT: "module-name": "mod"
+// CHECK: }
+// CHECK: ],
+
+// Check that result0 and result2 compute different hashes because
+// the working directory optmization is turned off for result2.
+// SKIPOPT: {
+// SKIPOPT-NEXT: "modules": [
+// SKIPOPT-NEXT: {
+// SKIPOPT-NEXT: "clang-module-deps": [],
+// SKIPOPT: "context-hash": "[[HASH0:.*]]",
+// SKIPOPT: }
+// SKIPOPT: "translation-units": [
+// SKIPOPT: {
+// SKIPOPT: "commands": [
+// SKIPOPT: {
+// SKIPOPT-NEXT: "clang-context-hash": "{{.*}}",
+// SKIPOPT-NEXT: "clang-module-deps": [
+// SKIPOPT-NEXT: {
+// SKIPOPT-NEXT: "context-hash": "[[HASH0]]",
+// SKIPOPT-NEXT: "module-name": "mod"
+// SKIPOPT: }
+// SKIPOPT: ],
+// SKIPOPT: {
+// SKIPOPT-NEXT: "modules": [
+// SKIPOPT-NEXT: {
+// SKIPOPT-NEXT: "clang-module-deps": [],
+// SKIPOPT-NOT: "context-hash": "[[HASH0]]",
+// SKIPOPT: "context-hash": "[[HASH2:.*]]",
+// SKIPOPT: }
+// SKIPOPT: "translation-units": [
+// SKIPOPT: {
+// SKIPOPT: "commands": [
+// SKIPOPT: {
+// SKIPOPT-NEXT: "clang-context-hash": "{{.*}}",
+// SKIPOPT-NEXT: "clang-module-deps": [
+// SKIPOPT-NEXT: {
+// SKIPOPT-NOT: "context-hash": "[[HASH0]]",
+// SKIPOPT-NEXT: "context-hash": "[[HASH2]]"
+// SKIPOPT-NEXT: "module-name": "mod"
+// SKIPOPT: }
+// SKIPOPT: ],
+
diff --git a/clang/test/ClangScanDeps/working-dir.m
b/clang/test/ClangScanDeps/working-dir.m
index a04f8c2486b98d..c6b7b1988d3cf7 100644
--- a/clang/test/ClangScanDeps/working-dir.m
+++ b/clang/test/ClangScanDeps/working-dir.m
@@ -2,7 +2,7 @@
// RUN: split-file %s %t
// RUN: sed -e "s|DIR|%/t|g" %t/build/compile-commands.json.in >
%t/build/compile-commands.json
// RUN: clang-scan-deps -compilation-database %t/build/compile-commands.json \
-// RUN: -j 1 -format experimental-full --optimize-args=all > %t/deps.db
+// RUN: -j 1 -format experimental-full
--optimize-args=header-search,system-warnings,vfs,canonicalize-macros >
%t/deps.db
// RUN: cat %t/deps.db | sed 's:\\\\\?:/:g' | FileCheck %s -DPREFIX=%/t
// Check that there are two separate modules hashes. One for each working dir.
diff --git a/clang/tools/clang-scan-deps/ClangScanDeps.cpp
b/clang/tools/clang-scan-deps/ClangScanDeps.cpp
index 709dc513be2811..8d429534a20073 100644
--- a/clang/tools/clang-scan-deps/ClangScanDeps.cpp
+++ b/clang/tools/clang-scan-deps/ClangScanDeps.cpp
@@ -164,6 +164,8 @@ static void ParseArgs(int argc, char **argv) {
.Case("system-warnings", ScanningOptimizations::SystemWarnings)
.Case("vfs", ScanningOptimizations::VFS)
.Case("canonicalize-macros", ScanningOptimizations::Macros)
+ .Case("ignore-current-working-dir",
+ ScanningOptimizations::IgnoreCWD)
.Case("all", ScanningOptimizations::All)
.Default(std::nullopt);
if (!Optimization) {
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