hsmhsm added inline comments.
================ Comment at: clang/lib/CodeGen/CGExpr.cpp:151 + // allocas. + Builder.CreateStore(Init, Var); } ---------------- jdoerfert wrote: > hsmhsm wrote: > > jdoerfert wrote: > > > I'm not even sure this is necessarily correct. > > > > > > How do we know the new store is not inside a loop and might write the > > > value more than once, potentially overwriting a value set later? > > > > > > Aside from that (important) question, you need to update the > > > documentation of the function. It doesn't correspond to the new semantics > > > anymore. > > > > > I am not convinced with above comments -Because, this code neither changes > > the address nor the initializer > > (https://github.com/llvm/llvm-project/blob/main/clang/lib/CodeGen/CodeGenFunction.h#L2548), > > but only a place where the initialization happens. > > > > Further, as the documentation says, the initializer must be a constant or > > function argument (and surprisingly, I do not see any assertion about it). > > Hence, even if the initialization happens within the loop, loop invariant > > code motion pass should detect it. > > > > That said, if we think, it is better to keep the initialization within > > entry block, we can do it at the end of the block. > What the initial value is is irrelevant. Arguing LICM should take care of it > is also not helpful. Changing the location of the initialization is in itself > a problem: > > Before: > ``` > a = alloca > a = 0; // init is in the entry block > for (...) { > use(a); > a = a + 1; > } > ``` > > After, potentially: > ``` > a = alloca > for (...) { > a = 0; // init is now at the builder insertion point > use(a); > a = a + 1; > } > ``` Clarification - I am not trying to argue anything here with anybody, I am trying to defend myself, where I feel I am right as per my knowledge. If I realize that I am at false later, then I correct myself, but I am not arguing, and will never ever do. Ok, I will try to fix it from the practical point of view. But, I still think as follows - From theoretical/good programming/good front-end code generation perspective, initialization of something will never happen within construct like loop, otherwise initialization has no meaning at all. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D110257/new/ https://reviews.llvm.org/D110257 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
