On Thu, Jan 11, 2024 at 11:18 AM Richard Biener <richard.guent...@gmail.com> wrote: > > On Thu, Jan 11, 2024 at 11:20 AM juzhe.zh...@rivai.ai > <juzhe.zh...@rivai.ai> wrote: > > > > Ok I see your idea and we need to adjust scalar_to_vec accurately. Inside > > the loop we have these 2 scalar_to_vec: > > > > 1. MIN_EXPR <patt_28, 15> 1 times scalar_to_vec costs 1 in prologue > > > > This scalar_to_vec cost should be 0 or 1 since it only generate single > > instructions: vmv.v.i v16,15 > > > > 2. 32872 >> patt_26 1 times scalar_to_vec costs 1 in prologue > > > > This cost should be higher since it cost 3 instructions: > > li a4,-32768 > > addiw a4,a4,104 > > vmv.v.x v16,a4 > > > > Am I correct ? > > > > I guess if we cost 1 case as 1 cost and 2 case as 3 cost. Then we will be > > good. > > The cost model interface isn't set up very well to cost different constants > differently. For scalar_to_vec we should get the backend the actual scalar > to duplicate but we don't.
It's similar for permutes btw. My plan was always to defer changes to when we only have SLP since there all invariants are represented by SLP nodes which we can hand down. > > ________________________________ > > juzhe.zh...@rivai.ai > > > > > > From: Robin Dapp > > Date: 2024-01-11 18:14 > > To: juzhe.zh...@rivai.ai; Richard Biener > > CC: rdapp.gcc; gcc-patches; kito.cheng; Kito.cheng; jeffreyalaw > > Subject: Re: [PATCH] RISC-V: Increase scalar_to_vec_cost from 1 to 3 > > > Yeah... I just noticed. I should set it as 4 to fix it with biggest VLEN > > > size, > > > that is, -march=rv64gcv_zvl4096b --param=riscv-autovec-lmul=m8... > > > > > > I am confused now how to fix this case. > > > > 4 is definitely too high compared to a regular instruction. > > vmv.vx could even be zero-cost for constants. > > > > To catch constants we could add handling in add_stmt_cost, inspecting > > the stmt directly. > > > > Regards > > Robin > >
