[clang] 54eea61 - add -fpch-codegen/debuginfo mapping to -fmodules-codegen/debuginfo
Luboš Luňák via cfe-commits
cfe-commits at lists.llvm.org
Wed Jul 22 01:23:09 PDT 2020
Author: Luboš Luňák
Date: 2020-07-22T10:21:53+02:00
New Revision: 54eea6127c4d77db03787b7c55765632fb9a6f1c
URL: https://github.com/llvm/llvm-project/commit/54eea6127c4d77db03787b7c55765632fb9a6f1c
DIFF: https://github.com/llvm/llvm-project/commit/54eea6127c4d77db03787b7c55765632fb9a6f1c.diff
LOG: add -fpch-codegen/debuginfo mapping to -fmodules-codegen/debuginfo
Using -fmodules-* options for PCHs is a bit confusing, so add -fpch-*
variants. Having extra options also makes it simple to do a configure
check for the feature.
Also document the options in the release notes.
Differential Revision: https://reviews.llvm.org/D83623
Added:
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Driver/Options.td
clang/lib/Driver/ToolChains/Clang.cpp
clang/test/Driver/pch-codegen.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 21689c5c5d85..9274081c4d62 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -63,6 +63,32 @@ New Compiler Flags
- ...
+- -fpch-codegen and -fpch-debuginfo generate shared code and/or debuginfo
+ for contents of a precompiled header in a separate object file. This object
+ file needs to be linked in, but its contents do not need to be generated
+ for other objects using the precompiled header. This should usually save
+ compile time. If not using clang-cl, the separate object file needs to
+ be created explicitly from the precompiled header.
+ Example of use:
+
+ .. code-block:: console
+
+ $ clang++ -x c++-header header.h -o header.pch -fpch-codegen -fpch-debuginfo
+ $ clang++ -c header.pch -o shared.o
+ $ clang++ -c source.cpp -o source.o -include-pch header.pch
+ $ clang++ -o binary source.o shared.o
+
+ - Using -fpch-instantiate-templates when generating the precompiled header
+ usually increases the amount of code/debuginfo that can be shared.
+ - In some cases, especially when building with optimizations enabled, using
+ -fpch-codegen may generate so much code in the shared object that compiling
+ it may be a net loss in build time.
+ - Since headers may bring in private symbols of other libraries, it may be
+ sometimes necessary to discard unused symbols (such as by adding
+ -Wl,--gc-sections on ELF platforms to the linking command, and possibly
+ adding -fdata-sections -ffunction-sections to the command generating
+ the shared object).
+
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index c2d349866814..700a5c4578f6 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1440,6 +1440,10 @@ def fpch_instantiate_templates:
def fno_pch_instantiate_templates:
Flag <["-"], "fno-pch-instantiate-templates">,
Group<f_Group>, Flags<[CC1Option]>;
+defm pch_codegen: OptInFFlag<"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: OptInFFlag<"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 fmodules : Flag <["-"], "fmodules">, Group<f_Group>,
Flags<[DriverOption, CC1Option]>,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8ce7e20408ab..7a73eea013bd 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5642,6 +5642,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (Args.hasFlag(options::OPT_fpch_instantiate_templates,
options::OPT_fno_pch_instantiate_templates, false))
CmdArgs.push_back("-fpch-instantiate-templates");
+ if (Args.hasFlag(options::OPT_fpch_codegen, options::OPT_fno_pch_codegen,
+ false))
+ CmdArgs.push_back("-fmodules-codegen");
+ if (Args.hasFlag(options::OPT_fpch_debuginfo, options::OPT_fno_pch_debuginfo,
+ false))
+ CmdArgs.push_back("-fmodules-debuginfo");
Args.AddLastArg(CmdArgs, options::OPT_fexperimental_new_pass_manager,
options::OPT_fno_experimental_new_pass_manager);
diff --git a/clang/test/Driver/pch-codegen.cpp b/clang/test/Driver/pch-codegen.cpp
index 1b125107fb28..c6b6d9217e42 100644
--- a/clang/test/Driver/pch-codegen.cpp
+++ b/clang/test/Driver/pch-codegen.cpp
@@ -7,21 +7,21 @@
// CHECK-PCH-CREATE-NOT: -fmodules-codegen
// CHECK-PCH-CREATE-NOT: -fmodules-debuginfo
-// Create PCH with -fmodules-codegen.
-// RUN: %clang -x c++-header -Xclang -fmodules-codegen %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CODEGEN-CREATE
+// Create PCH with -fpch-codegen.
+// RUN: %clang -x c++-header -fpch-codegen %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CODEGEN-CREATE
// CHECK-PCH-CODEGEN-CREATE: -emit-pch
// CHECK-PCH-CODEGEN-CREATE: -fmodules-codegen
// CHECK-PCH-CODEGEN-CREATE: "-x" "c++-header"
// CHECK-PCH-CODEGEN-CREATE-NOT: -fmodules-debuginfo
-// Create PCH with -fmodules-debuginfo.
-// RUN: %clang -x c++-header -Xclang -fmodules-debuginfo %S/../Modules/Inputs/codegen-flags/foo.h -g -o %t/foo-di.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-DEBUGINFO-CREATE
+// Create PCH with -fpch-debuginfo.
+// RUN: %clang -x c++-header -fpch-debuginfo %S/../Modules/Inputs/codegen-flags/foo.h -g -o %t/foo-di.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-DEBUGINFO-CREATE
// CHECK-PCH-DEBUGINFO-CREATE: -emit-pch
// CHECK-PCH-DEBUGINFO-CREATE: -fmodules-debuginfo
// CHECK-PCH-DEBUGINFO-CREATE: "-x" "c++-header"
// CHECK-PCH-DEBUGINFO-CREATE-NOT: -fmodules-codegen
-// Create PCH's object file for -fmodules-codegen.
+// Create PCH's object file for -fpch-codegen.
// RUN: touch %t/foo-cg.pch
// RUN: %clang -c %t/foo-cg.pch -o %t/foo-cg.o -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CODEGEN-OBJ
// CHECK-PCH-CODEGEN-OBJ: -emit-obj
@@ -29,7 +29,7 @@
// CHECK-PCH-CODEGEN-OBJ: "-o" "{{.*}}foo-cg.o"
// CHECK-PCH-CODEGEN-OBJ: "-x" "precompiled-header"
-// Create PCH's object file for -fmodules-debuginfo.
+// Create PCH's object file for -fpch-debuginfo.
// RUN: touch %t/foo-di.pch
// RUN: %clang -c %t/foo-di.pch -g -o %t/foo-di.o -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-DEBUGINFO-OBJ
// CHECK-PCH-DEBUGINFO-OBJ: -emit-obj
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