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.
48 lines
1.3 KiB
C++
48 lines
1.3 KiB
C++
// RUN: rm -rf %t
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// RUN: mkdir -p %t
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// RUN: split-file %s %t
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//
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// RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-module-interface -o %t/A.pcm
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// RUN: %clang_cc1 -std=c++20 %t/Use.cpp -fprebuilt-module-path=%t -fsyntax-only -verify
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// RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-reduced-module-interface -o %t/A.pcm
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// RUN: %clang_cc1 -std=c++20 %t/Use.cpp -fprebuilt-module-path=%t -fsyntax-only -verify
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//--- placement.h
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namespace std {
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using size_t = decltype(sizeof(0));
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}
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void *operator new(std::size_t, void *p) { return p; }
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//--- A.cppm
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module;
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#include "placement.h"
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export module A;
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export template<class T>
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struct A {
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A(void *p) : ptr(new (p) T(43)) {}
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private:
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void *ptr;
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};
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export struct B {
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B(void *p) : ptr(new (p) int(43)) {}
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private:
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void *ptr;
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};
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// The use of operator new in the current module unit is only in the non-inline
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// function definitions. So it may be optimized out.
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using ::operator new;
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//--- Use.cpp
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// expected-no-diagnostics
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import A;
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void bar(int *);
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void foo(void *ptr) {
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A<int> a(nullptr); // Good. It should be OK to construct A.
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B b(nullptr);
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void *p = ::operator new(sizeof(int), ptr); // Bad. The placement allocation in module A is not visible.
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void *q = new (ptr) int(43); // Good. We don't call the placement allocation function directly.
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}
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