https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110202
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |hjl.tools at gmail dot com, | |jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Well, there is nothing magic on exactly 0x55 immediate, there are 256 possible immediates, most of them use all of A, B, C, some of them use just A, B, others just B, C, others just A, C, others just A, others just B, others just C, others none of them. And I must say I don't immediately see easy rules how to find out from the immediate value which set is which, so unless we find some easy rule for that, we'd need to hardcode the mapping between the 256 values to a bitmask which inputs are actually used. And then the question is how to represent that in RTL to make it clear that some operands are mentioned but their value isn't really used.