The ISA spec itself suggests one fusion - that of mul and mulh (lower and upper halves of n-bit * n-bit -> 2n-bit product). The only other source I know of was

The ISA spec itself suggests one fusion - that of mul and mulh (lower and upper halves of n-bit * n-bit -> 2n-bit product). The only other source I know of was this 2016 paper that suggested specific macro fusions. https://arxiv.org/abs/1607.02318 https://arxiv.org/abs/1607.02318 This predates the B extension so some of those fusions are dedicated instructions now, but I suppose Xiangshan still implements them for the sake of software that was not compiled with B enabled.