[C++20] [Modules] Introduce reduced BMI (#75894)
Close https://github.com/llvm/llvm-project/issues/71034
See
https://discourse.llvm.org/t/rfc-c-20-modules-introduce-thin-bmi-and-decls-hash/74755
This patch introduces reduced BMI, which doesn't contain the definitions
of functions and variables if its definitions won't contribute to the
ABI.
Testing is a big part of the patch. We want to make sure the reduced BMI
contains the same behavior with the existing and relatively stable
fatBMI. This is pretty helpful for further reduction.
The user interfaces part it left to following patches to ease the
reviewing.
diff --git a/clang/test/Modules/pr62359.cppm b/clang/test/Modules/pr62359.cppm
index 4632457..69acc3c 100644
--- a/clang/test/Modules/pr62359.cppm
+++ b/clang/test/Modules/pr62359.cppm
@@ -12,6 +12,22 @@
// RUN: %clang_cc1 -std=c++20 -fopenmp %t/use.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only -verify
// RUN: %clang_cc1 -std=c++20 -fopenmp %t/use2.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only -verify
+// Test again with reduced BMI
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -emit-reduced-module-interface %t/Hello.cppm -o %t/Hello.pcm
+// RUN: not %clang_cc1 -std=c++20 -fopenmp %t/use.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only \
+// RUN: 2>&1 | FileCheck %t/use.cpp
+// RUN: not %clang_cc1 -std=c++20 -fopenmp %t/use2.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only \
+// RUN: 2>&1 | FileCheck %t/use2.cpp
+//
+// RUN: %clang_cc1 -std=c++20 -fopenmp -emit-reduced-module-interface %t/Hello.cppm -o %t/Hello.pcm
+// RUN: %clang_cc1 -std=c++20 -fopenmp %t/use.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only -verify
+// RUN: %clang_cc1 -std=c++20 -fopenmp %t/use2.cpp -fmodule-file=hello=%t/Hello.pcm -fsyntax-only -verify
+
+
//--- Hello.cppm
export module hello;
export void hello() {
