Reland: "[Frontend][PCH]-Add support for ignoring PCH options (-ignore-pch). (#142409)" #143614
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-driver Author: Ying Yi (MaggieYingYi) ChangesVisual Studio has an argument to ignore all PCH related switches. clang-cl has also support option /Y-. Having the same option in clang would be helpful. This commit is to add support for ignoring PCH options (-ignore-pch). The commit includes:
Full diff: https://github.com/llvm/llvm-project/pull/143614.diff 8 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f36c82bff2ef8..86287b28f0bf8 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -339,6 +339,8 @@ New Compiler Flags
- New option ``-Wnrvo`` added and disabled by default to warn about missed NRVO opportunities.
+- New option ``-ignore-pch`` added to disable precompiled headers. It overrides ``-emit-pch`` and ``-include-pch``. (#GH142409, `PCHDocs <https://clang.llvm.org/docs/UsersManual.html#ignoring-a-pch-file>`_).
+
Deprecated Compiler Flags
-------------------------
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 62844f7e6a2fa..284a404026dfe 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1458,6 +1458,19 @@ will be processed from the PCH file. Otherwise, Clang will report an error.
``test.h`` since ``test.h`` was included directly in the source file and not
specified on the command line using ``-include-pch``.
+Ignoring a PCH File
+^^^^^^^^^^^^^^^^^^^
+
+To ignore PCH options, a `-ignore-pch` option is passed to ``clang``:
+
+.. code-block:: console
+
+ $ clang -x c-header test.h -Xclang -ignore-pch -o test.h.pch
+ $ clang -include-pch test.h.pch -Xclang -ignore-pch test.c -o test
+
+This option disables precompiled headers, overrides -emit-pch and -include-pch.
+test.h.pch is not generated and not used as a prefix header.
+
Relocatable PCH Files
^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 3582efd7721b0..66d3dc921816d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3348,6 +3348,9 @@ defm pch_codegen: OptInCC1FFlag<"pch-codegen", "Generate ", "Do not generate ",
"code for uses of this PCH that assumes an explicit object file will be built for the PCH">;
defm pch_debuginfo: OptInCC1FFlag<"pch-debuginfo", "Generate ", "Do not generate ",
"debug info for types in an object file built from this PCH and do not generate them elsewhere">;
+def ignore_pch : Flag<["-"], "ignore-pch">, Group<f_Group>,
+ Visibility<[ClangOption]>,
+ HelpText<"Disable precompiled headers, overrides -emit-pch and -include-pch">;
def fimplicit_module_maps : Flag <["-"], "fimplicit-module-maps">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 80728daca03c9..21489c8b0cde9 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -4331,6 +4331,14 @@ void Driver::handleArguments(Compilation &C, DerivedArgList &Args,
YcArg = YuArg = nullptr;
}
+ if (Args.hasArg(options::OPT_include_pch) &&
+ Args.hasArg(options::OPT_ignore_pch)) {
+ // If -ignore-pch is used, -include-pch is disabled. Since -emit-pch is
+ // CC1option, it will not be added to command argments if -ignore-pch is
+ // used.
+ Args.eraseArg(options::OPT_include_pch);
+ }
+
bool LinkOnly = phases::Link == FinalPhase && Inputs.size() > 0;
for (auto &I : Inputs) {
types::ID InputType = I.first;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index a74fa81f3cf5b..2d676aa0b9c8e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5184,7 +5184,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back("-emit-module-interface");
else if (JA.getType() == types::TY_HeaderUnit)
CmdArgs.push_back("-emit-header-unit");
- else
+ else if (!Args.hasArg(options::OPT_ignore_pch))
CmdArgs.push_back("-emit-pch");
} else if (isa<VerifyPCHJobAction>(JA)) {
CmdArgs.push_back("-verify-pch");
@@ -5241,7 +5241,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
} else if (JA.getType() == types::TY_PP_Asm) {
CmdArgs.push_back("-S");
} else if (JA.getType() == types::TY_AST) {
- CmdArgs.push_back("-emit-pch");
+ if (!Args.hasArg(options::OPT_ignore_pch))
+ CmdArgs.push_back("-emit-pch");
} else if (JA.getType() == types::TY_ModuleFile) {
CmdArgs.push_back("-module-file-info");
} else if (JA.getType() == types::TY_RewrittenObjC) {
diff --git a/clang/test/Driver/ignored-pch.cpp b/clang/test/Driver/ignored-pch.cpp
new file mode 100644
index 0000000000000..b237fc3cba57d
--- /dev/null
+++ b/clang/test/Driver/ignored-pch.cpp
@@ -0,0 +1,19 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// Create PCH without -ignore-pch.
+// RUN: %clang -x c++-header %S/../Modules/Inputs/codegen-flags/foo.h -### 2>&1 | FileCheck %s -check-prefix=CHECK-EMIT-PCH
+// RUN: %clang -x c++-header %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo.h.pch
+// RUN: %clang %s -include-pch %t/foo.h.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-INCLUDE-PCH
+// RUN: %clang %s -emit-ast -include-pch %t/foo.h.pch -### 2>&1 | FileCheck %s -check-prefixes=CHECK-EMIT-PCH,CHECK-INCLUDE-PCH
+
+
+// Create PCH with -ignore-pch.
+// RUN: %clang -x c++-header -ignore-pch %S/../Modules/Inputs/codegen-flags/foo.h -### 2>&1 | FileCheck %s -check-prefix=CHECK-IGNORE-PCH
+// RUN: %clang %s -ignore-pch -include-pch %t/foo.h.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-IGNORE-PCH
+// RUN: %clang %s -ignore-pch -emit-ast -include-pch %t/foo.h.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-IGNORE-PCH
+
+// CHECK-EMIT-PCH: -emit-pch
+// CHECK-INCLUDE-PCH: -include-pch
+// CHECK-IGNORE-PCH-NOT: -emit-pch
+// CHECK-IGNORE-PCH-NOT: -include-pch
diff --git a/clang/test/PCH/Inputs/ignored-pch.h b/clang/test/PCH/Inputs/ignored-pch.h
new file mode 100644
index 0000000000000..56047037c331f
--- /dev/null
+++ b/clang/test/PCH/Inputs/ignored-pch.h
@@ -0,0 +1,6 @@
+#ifndef IGNORED_PCH_H
+#define IGNORED_PCH_H
+inline int f() {
+ return 42;
+}
+#endif // IGNORED_PCH_H
diff --git a/clang/test/PCH/ignored-pch.c b/clang/test/PCH/ignored-pch.c
new file mode 100644
index 0000000000000..5b64582cba618
--- /dev/null
+++ b/clang/test/PCH/ignored-pch.c
@@ -0,0 +1,113 @@
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -o %t.ll
+// RUN: ls %t.pch | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -o %t.pch
+// RUN: %clang %s -emit-ast -include-pch %t.pch -o %t.ll
+// RUN: ls %t.pch | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Check that -ignore-pch causes -emit-pch and -include-pch options to be ignored.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH-ERROR %s
+// RUN: ls %t.ll 2>&1 | FileCheck --check-prefix=CHECK-OBJ %s
+
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -emit-ast %s -include-pch %t.pch -ignore-pch -o %t.ll
+// RUN: not ls %t.ll 2>&1 | FileCheck --check-prefix=CHECK-OBJ-ERROR %s
+
+// Check that -ignore-pch works for multiple PCH related options.
+// Test with -building-pch-with-obj.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -building-pch-with-obj -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -Xclang -building-pch-with-obj -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH-ERROR %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fallow-pch-with-compiler-errors.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -fallow-pch-with-compiler-errors -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -Xclang -fallow-pch-with-compiler-errors -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH-ERROR %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fallow-pch-with-different-modules-cache-path.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -fallow-pch-with-different-modules-cache-path -o %t.pch
+// RUN: %clang -S -emit-llvm %s -ignore-pch -include-pch %t.pch -Xclang -fallow-pch-with-different-modules-cache-path -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH-ERROR %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fpch-codegen.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -fpch-codegen -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -fpch-codegen -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH-ERROR %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fpch-debuginfo.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -fpch-debuginfo -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -fpch-debuginfo -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fpch-instantiate-templates.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -fpch-instantiate-templates -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -fpch-instantiate-templates -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fno-pch-timestamp.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -fno-pch-timestamp -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -Xclang -fno-pch-timestamp -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -fno-validate-pch.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -fno-validate-pch -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -Xclang -fno-validate-pch -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -relocatable-pch.
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -relocatable-pch -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -relocatable-pch -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+// Test with -pch-through-hdrstop-create/-pch-through-hdrstop-use
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -ignore-pch -Xclang -pch-through-hdrstop-create -o %t.pch
+// RUN: %clang -S -emit-llvm %s -include-pch %t.pch -ignore-pch -Xclang -pch-through-hdrstop-use -o %t.ll
+// RUN: not ls %t.pch 2>&1 | FileCheck --check-prefix=CHECK-PCH %s
+// RUN: ls %t.ll | FileCheck --check-prefix=CHECK-OBJ %s
+
+
+// Test with AST dump output:
+// RUN: rm -rf %t.pch %t.ll
+// RUN: %clang -x c-header %S/Inputs/ignored-pch.h -o %t.pch
+// RUN: %clang %s -include-pch %t.pch -Xclang -ast-dump-all -c | FileCheck --check-prefix=CHECK-AST-PCH %s
+// RUN: %clang %s -include-pch %t.pch -ignore-pch -Xclang -ast-dump-all -c | FileCheck --check-prefix=CHECK-AST %s
+
+// CHECK-PCH: ignored-pch.c.{{.*}}.pch
+// CHECK-OBJ: ignored-pch.c.{{.*}}.ll
+// CHECK-PCH-ERROR: ignored-pch.c.{{.*}}.pch{{'?}}: No such file or directory
+// CHECK-OBJ-ERROR: ignored-pch.c.{{.*}}.ll{{'?}}: No such file or directory
+// CHECK-AST-PCH: <undeserialized declarations>
+// CHECK-AST-NOT: <undeserialized declarations>
+
+#pragma hdrstop
+#include "Inputs/ignored-pch.h"
+int main() {
+ return f();
+}
|
mizvekov
changed the title
mizvekov
approved these changes
Jun 10, 2025
Thanks @mizvekov.
Yes, only ignore PCH option when When I implemented Thanks @dyung for helping me check the build and test on MacOS. check-all passed on mac.
Thanks, I will add it in commit message. |
MaskRay
reviewed
Jun 11, 2025
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…-pch). (llvm#142409)" Visual Studio has an argument to ignore all PCH related switches. clang-cl has also support option /Y-. Having the same option in clang would be helpful. This commit is to add support for ignoring PCH options (-ignore-pch). The commit includes: 1. Implement -ignore-pch as a Driver option. 2. Add a Driver test and a PCH test. 3. Add a section of -ignore-pch to user manual. 4. Add a release note for the new option '-ignore-pch'. The change since the original landing: 1. preprocessing-only mode doesn't imply that -include-pch is disabled. Co-authored-by: Matheus Izvekov <[email protected]> Update the test using the header file from a same test directory.
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Visual Studio has an argument to ignore all PCH related switches. clang-cl has also support option /Y-. Having the same option in clang would be helpful. This commit is to add support for ignoring PCH options (-ignore-pch).
The commit includes: