[clang] b5dffd4 - [C++20] [Modules] Don't emit function bodies which is noinline and av… (#68501)

[via cfe-commits]

Author: Chuanqi Xu
Date: 2023-10-10T09:47:13+08:00
New Revision: b5dffd4957dfb58c73e168a3d9b6967f03b23a6c

URL: https://github.com/llvm/llvm-project/commit/b5dffd4957dfb58c73e168a3d9b6967f03b23a6c
DIFF: https://github.com/llvm/llvm-project/commit/b5dffd4957dfb58c73e168a3d9b6967f03b23a6c.diff

LOG: [C++20] [Modules] Don't emit function bodies which is noinline and av… (#68501)

…ailabl externally

A workaround for https://github.com/llvm/llvm-project/issues/60996

As the title suggested, we can avoid emitting available externally
functions which is marked as noinline already. Such functions should
contribute nothing for optimizations.

The update for docs will be sent seperately if this got approved.

Added: 
    clang/test/Modules/no-import-func-body.cppm

Modified: 
    clang/lib/CodeGen/CodeGenModule.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index d6ab7b3567b9b03..754377bed7f7eef 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3849,6 +3849,9 @@ bool CodeGenModule::shouldEmitFunction(GlobalDecl GD) {
   if (CodeGenOpts.OptimizationLevel == 0 && !F->hasAttr<AlwaysInlineAttr>())
     return false;
 
+  if (F->hasAttr<NoInlineAttr>())
+    return false;
+
   if (F->hasAttr<DLLImportAttr>() && !F->hasAttr<AlwaysInlineAttr>()) {
     // Check whether it would be safe to inline this dllimport function.
     DLLImportFunctionVisitor Visitor;

diff  --git a/clang/test/Modules/no-import-func-body.cppm b/clang/test/Modules/no-import-func-body.cppm
new file mode 100644
index 000000000000000..9a111dca9855c09
--- /dev/null
+++ b/clang/test/Modules/no-import-func-body.cppm
@@ -0,0 +1,45 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+//
+// RUN: %clang_cc1 -std=c++20 -O1 -triple %itanium_abi_triple %t/a.cppm \
+// RUN:     -emit-module-interface -o %t/a.pcm
+// RUN: %clang_cc1 -std=c++20 -O1 -triple %itanium_abi_triple %t/b.cppm \
+// RUN:     -emit-module-interface -fprebuilt-module-path=%t -o %t/b.pcm
+// RUN: %clang_cc1 -std=c++20 -O1 -triple %itanium_abi_triple %t/c.cppm \
+// RUN:     -emit-module-interface -fprebuilt-module-path=%t -o %t/c.pcm
+// RUN: %clang_cc1 -std=c++20 -O1 -triple %itanium_abi_triple %t/c.pcm -S \
+// RUN:     -emit-llvm -disable-llvm-passes -o - | FileCheck %t/c.cppm
+
+//--- a.cppm
+export module a;
+export int a() {
+    return 43;
+}
+export __attribute__((noinline)) int a_noinline() {
+    return 44;
+}
+
+//--- b.cppm
+export module b;
+export import a;
+export int b() {
+    return 43 + a();
+}
+
+export __attribute__((noinline)) int b_noinline() {
+    return 43 + a();
+}
+
+//--- c.cppm
+export module c;
+export import b;
+export int c() {
+    return 43 + b() + a() + b_noinline() + a_noinline();
+}
+
+// CHECK: define{{.*}}available_externally{{.*}}@_ZW1b1bv(
+// CHECK: define{{.*}}available_externally{{.*}}@_ZW1a1av(
+
+// CHECK: declare{{.*}}@_ZW1b10b_noinlinev()
+// CHECK: declare{{.*}}@_ZW1a10a_noinlinev()