Hi! On Thu, Aug 26, 2021 at 05:28:42PM -0400, Michael Meissner wrote: > On Thu, Aug 26, 2021 at 02:17:57PM -0500, will schmidt wrote: > > On Wed, 2021-08-25 at 15:46 -0400, Michael Meissner wrote: > > > Generate XXSPLTIDP on power10. > > > > > > I have added a temporary switch (-mxxspltidp) to control whether or not > > > the > > > XXSPLTIDP instruction is generated. > > > > How temporary? > > Until we decide we no longer need to disable the option to do tests. Probably > at the end of stage1.
Don't do it at all please. If it is useful to disable some new strategy for generating constants, a (temporary or at least undocumented) flag for that can be handy. But a flag to disable separate insns is a liability, it makes the compiler much more fragile, makes changing the compiler hard because of all the surprises hidden. > > > (xxspltidp_operand): New predicate. > > > > Will there ever be another instruction using the SF/DF CONST_DOUBLE or > > V2DF CONST_VECTOR ? I tentatively question the name of the operand, > > but defer.. > > This is the convention I've used for adding other instructions like xxspltib. The only reason it is a good idea here is because of the strange behaviour this insn has with single precision subnormals. In general a better name here would be something like "sf_as_int_operand". The insn should probably not allow anything else than bit patterns, not floating point constants, have a separate pattern for that (that can then forward to the integer one). > This way we have just one place that centralizes the knowledge about the > instruction. That one place should be the define_insn for it. Segher
