xbolva00 added a comment. In D86844#2484639 <https://reviews.llvm.org/D86844#2484639>, @atmnpatel wrote:
> In D86844#2484568 <https://reviews.llvm.org/D86844#2484568>, @fhahn wrote: > >> In D86844#2481922 <https://reviews.llvm.org/D86844#2481922>, @xbolva00 wrote: >> >>> int a, b; >>> >>> int f(void) { >>> while (1) { >>> if (a != b) return 1; >>> } >>> return 0; >>> } >>> >>> int g(int a, int b) { >>> while (1) { >>> if (a != b) return 1; >>> } >>> return 0; >>> } >>> >>> LLVM does not catch these cases; gcc does. >>> >>> https://godbolt.org/z/jW7son >> >> Looks like `must progress` does not get added? If it gets added to the IR >> the loops get removed: https://godbolt.org/z/77v17P > > I might be misunderstanding the standard here but since 1 is a non-zero > constant expression, it can't be assumed to terminate by the implementation > right? The relevant section from C11 at least is "An iteration statement > whose controlling expression is not a constant expression that performs > [explanation of what it deems as progress] may be assumed by the > implementation to terminate" (C11 6.8.5 p6). I think these cases fall outside > of the scope of this particular change ... For C yes, but are there such rules for C++? GCC in c++ mode does not check for non-zero constant expr and happily performs this optimization. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D86844/new/ https://reviews.llvm.org/D86844 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
