f21ead0675
Following of https://github.com/llvm/llvm-project/pull/76930 This follows the idea of "only writes what we writes", which I think is the most natural and efficient way to implement this optimization. We start writing the BMI from the first declaration in module purview instead of the global module fragment, so that everything in the GMF untouched won't be written in the BMI naturally. The exception is, as I said in https://github.com/llvm/llvm-project/pull/76930, when we write a declaration we need to write its decl context, and when we write the decl context, we need to write everything from it. So when we see `std::vector`, we basically need to write everything under namespace std. This violates our intention. To fix this, this patch delays the writing of namespace in the GMF. From my local measurement, the size of the BMI decrease to 90M from 112M for a local modules build. I think this is significant. This feature will be covered under the experimental reduced BMI so that it won't affect any existing users. So I'd like to land this when the CI gets green. Documents will be added seperately.
59 lines
1.8 KiB
C++
59 lines
1.8 KiB
C++
// RUN: rm -rf %t
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// RUN: mkdir %t
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// RUN: split-file %s %t
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// RUN: %clang_cc1 -std=c++20 %t/std-10-4-ex2-interface.cppm -emit-reduced-module-interface \
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// RUN: -o %t/M.pcm -Wno-unused-value
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// RUN: %clang_cc1 -std=c++20 %t/std-10-4-ex2-implementation.cpp -fmodule-file=M=%t/M.pcm \
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// RUN: -fsyntax-only -verify -Wno-unused-value
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//--- std-10-4-ex2.h
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namespace N {
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struct X {};
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int d();
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int e();
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inline int f(X, int = d()) { return e(); }
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int g(X);
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int h(X);
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} // namespace N
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//--- std-10-4-ex2-interface.cppm
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module;
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#include "std-10-4-ex2.h"
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export module M;
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template <typename T> int use_f() {
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N::X x; // N::X, N, and :: are decl-reachable from use_f
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return f(x, 123); // N::f is decl-reachable from use_f,
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// N::e is indirectly decl-reachable from use_f
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// because it is decl-reachable from N::f, and
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// N::d is decl-reachable from use_f
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// because it is decl-reachable from N::f
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// even though it is not used in this call
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}
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template <typename T> int use_g() {
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N::X x; // N::X, N, and :: are decl-reachable from use_g
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return g((T(), x)); // N::g is not decl-reachable from use_g
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}
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template <typename T> int use_h() {
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N::X x; // N::X, N, and :: are decl-reachable from use_h
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return h((T(), x)); // N::h is not decl-reachable from use_h, but
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// N::h is decl-reachable from use_h<int>
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}
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int k = use_h<int>();
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// use_h<int> is decl-reachable from k, so
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// N::h is decl-reachable from k
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//--- std-10-4-ex2-implementation.cpp
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module M;
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int a = use_f<int>();
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int b = use_g<int>();
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// expected-error@std-10-4-ex2-interface.cppm:17 {{use of undeclared identifier 'g'}}
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// expected-note@-2 {{in instantiation of function template specialization 'use_g<int>' requested here}}
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int c = use_h<int>();
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