================ @@ -1817,27 +1804,29 @@ But with optimizations, things are different: │ │ └---------------------------------------┘ -It would be very unfortunate if we end up with worse performance after using modules. -The main concern is that when we compile a source file, the compiler needs to see the function body -of imported module units so that it can perform IPO (InterProcedural Optimization, primarily inlining -in practice) to optimize functions in current source file with the help of the information provided by -the imported module units. -In other words, the imported code would be processed again and again in importee units -by optimizations (including IPO itself). -The optimizations before IPO and the IPO itself are the most time-consuming part in whole compilation process. -So from this perspective, we might not be able to get the improvements described in the theory. -But we could still save the time for optimizations after IPO and the whole backend. - -Overall, at ``O0`` the implementations of functions defined in a module will not impact module users, -but at higher optimization levels the definitions of such functions are provided to user compilations for the -purposes of optimization (but definitions of these functions are still not included in the use's object file)- -this means the build speedup at higher optimization levels may be lower than expected given ``O0`` experience, -but does provide by more optimization opportunities. +It would be very unfortunate if we end up with worse performance when using +modules. The main concern is that when a source file is compiled, the compiler +needs to see the body of imported module units so that it can perform IPO +(InterProcedural Optimization, primarily inlining in practice) to optimize +functions in the current source file with the help of the information provided +by the imported module units. In other words, the imported code would be +processed again and again in importee units by optimizations (including IPO +itself). The optimizations before IPO and IPO itself are the most time-consuming +part in whole compilation process. So from this perspective, it might not be +possible to get the compile time improvements described in the theory, but +there could be time savings for optimizations after IPO and the whole backend. + +Overall, at ``-O0`` the implementations of functions defined in a module will +not impact module users, but at higher optimization levels the definitions of +such functions are provided to user compilations for the purposes of +optimization (but definitions of these functions are still not included in the +use's object file) -- this means the build speedup at higher optimization ---------------- Endilll wrote:
```suggestion use's object file). This means the build speedup at higher optimization ``` https://github.com/llvm/llvm-project/pull/90237 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits