> > > > When testing a extension, it is often necessary for a certain program > > > > not to > > > > need some kind of extension, such as the bitmanip extension, to > > > > evaluate the > > > > performance or codesize of the extension. However, the current multilib > > > > rules > > > > will report an error when it is not a superset of the MULTILIB_REQUIRED > > > > list, > > > > which will cause the program to be unable to link normally, thus > > > > failing to > > > > achieve the expected purpose. > > > > > > Hmm, I have troubles understanding what is going on here. What do you > > > refer to by saying: "it is not a superset of the MULTILIB_REQUIRED list"? > > > > This is a new matching rule added by kito for the multilib of riscv: > > https://github.com/gcc-mirror/gcc/commit/d72ca12b846a9f5c01674b280b1817876c77888f > > > > > There should be no problem with linking compiled modules together that > > > make use of different extensions, with the static linker figuring out the > > > combined set of extensions actually required at run time for the program > > > loader to consider, as long as the modules do not have contradicting > > > requirements, e.g. big vs little endianness or RV32 vs RV64. > > > > > > Can you give me a specific example (compilation options and multilibs > > > available) of a failure you refer to? > > > > A simple example: > > 1. Use "--disable-multilib --with-abi =lp64d --with-arch > > =rv64imafdc_zba_zbb_zbc_zbs" > > to build the toolchain". > > 2. Use the toolchain to test the impact of zba_zbb_zbc_zbs extensions on the > > performance and codesize of some functions or files in the program. > > > > In this case, I may need to use the command "-mabi=lp64d -march=rv64imafdc" > > for > > the compilation of a specific .c file in the program, which will cause the > > link to > > fail and throw the following error: "FATAL ERROR: Can't find suitable > > multilib set for > > '-march=rv64imafdc'/'-mabi=lp64d'". This does not satisfy the purpose of > > the test. > > I feel this case should be build with --with-arch =rv64imafdc and test > with -march=rv64imafdc and -march=rv64imafdc_zba_zbb_zbc_zbs, > but anyway I am OK with option :P
Yes, but with "--with-arch=rv64imafdc" building toolchains, the library will not contain zba_zbb_zbc_zbs extensions, so how can we quickly and easily eliminate the impact of not using zba_zbb_zbc_zbs extensions in a certain program on program performance and codesize? Although-mno-multilib-check is unsafe, it is useful during the development and testing phases. > > > > > I think this needs an option to turn off this check. Users sometimes, just > > as > > gcc uses the default multilib when it does not match the appropriate > > multilib, > > do not need the `security lock`, and should already understand the risks > > of using this option. > > > > > Is this something that could be solved without resorting to a possibly > > > dangerous hack, by making use of MULTILIB_REUSE? > > > > Regarding the use of MULTILIB_REUSE, I think kito's patch has already been > > explained > > and is currently implemented according to the new rules. > > https://github.com/gcc-mirror/gcc/commit/5ca9980fc86242505ffdaaf62bca1fd5db26550b > > > > > > > > Maciej > > > > Thanks, > > Jin
