Re: [PATCH V2] rs6000: Don't allow immediate value in the vsx_splat pattern [PR113950]
On Wed, Feb 28, 2024 at 11:58:15AM -0600, Peter Bergner wrote: > On 2/28/24 8:31 AM, Segher Boessenkool wrote: > > On Tue, Feb 27, 2024 at 04:50:02PM -0600, Peter Bergner wrote: > >> So it seems you're not NAKing the use of splat_input_operand, but > >> just that it needs more explanation in the git log entry, correct? > > > > I NAK the patch. _Of course_ there needs to be *something* done, there > > is a bug after all, it needs to be fixed. > > > > But no, there are big questions about if splat_input_operand is correct > > as well. This needs to be justified in the patch submission. > > Ok, then Jeevitha, repost the patch with the s/op1/operands[1]/ only change. > Jeevitha has already bootstrapped and regtested that change and it does > fix the bug. > > Clearly, the splat_input_operand change needs more discussion and would > be a follow-on patch...if we decide to do it at all. It is clear that input_operand is wrong. It isn't clear that splat_input_operand is correct though :-( Segher
Re: [PATCH V2] rs6000: Don't allow immediate value in the vsx_splat pattern [PR113950]
On 2/28/24 8:31 AM, Segher Boessenkool wrote: > On Tue, Feb 27, 2024 at 04:50:02PM -0600, Peter Bergner wrote: >> So it seems you're not NAKing the use of splat_input_operand, but >> just that it needs more explanation in the git log entry, correct? > > I NAK the patch. _Of course_ there needs to be *something* done, there > is a bug after all, it needs to be fixed. > > But no, there are big questions about if splat_input_operand is correct > as well. This needs to be justified in the patch submission. Ok, then Jeevitha, repost the patch with the s/op1/operands[1]/ only change. Jeevitha has already bootstrapped and regtested that change and it does fix the bug. Clearly, the splat_input_operand change needs more discussion and would be a follow-on patch...if we decide to do it at all. Peter
Re: [PATCH V2] rs6000: Don't allow immediate value in the vsx_splat pattern [PR113950]
On Tue, Feb 27, 2024 at 04:50:02PM -0600, Peter Bergner wrote: > On 2/27/24 6:40 AM, Segher Boessenkool wrote: > > On Tue, Feb 27, 2024 at 02:02:38AM +0530, jeevitha wrote: > > input_operand allows a lot of things that splat_input_operand does not, > > not just immediate operands. NAK. > > > > (For example, *all* memory is okay for input_operand, always). > > > > I'm not saying we do not want to restrict these things, but a commit > > that doesn't discuss this at all is not okay. Sorry. > > So it seems you're not NAKing the use of splat_input_operand, but > just that it needs more explanation in the git log entry, correct? I NAK the patch. _Of course_ there needs to be *something* done, there is a bug after all, it needs to be fixed. But no, there are big questions about if splat_input_operand is correct as well. This needs to be justified in the patch submission. > Yes, input_operand accepts a lot more things than splat_input_operand > does, but the multiple define_insns this define_expand feeds, uses > gpc_reg_operand, memory_operand and splat_input_operand for their > operands[1] operand (splat_input_operand accepts reg and mem too), > so it seems to match better what the patterns will be accepting and > I always thought that using predicates that more accurately reflect > what the define_insns expect/accept lead to better code gen. Still, it needs explanation why we allowed it before, but that was a mistake, or for some reason we do not need it. Sell your patch! :-) > Mike, was it just an oversight to not use splat_input_operand for the > vsx_splat_ expander or was input_operand a conscious decision? > > If input_operand was used purposely, then we can just fall back to > the s/op1/operands[1]/ change which we already know fixes the bug. input_operand allows all inputs for mov insns. It isn't suitable for any other instructions. Segher
Re: [PATCH V2] rs6000: Don't allow immediate value in the vsx_splat pattern [PR113950]
On 2/27/24 6:40 AM, Segher Boessenkool wrote: > On Tue, Feb 27, 2024 at 02:02:38AM +0530, jeevitha wrote: >> There is no immediate value splatting instruction in Power. Currently, those >> values need to be stored in a register or memory. To address this issue, I >> have updated the predicate for the second operand in vsx_splat to >> splat_input_operand and corrected the assignment of op1 to operands[1]. >> These changes ensure that operand1 is stored in a register. > > input_operand allows a lot of things that splat_input_operand does not, > not just immediate operands. NAK. > > (For example, *all* memory is okay for input_operand, always). > > I'm not saying we do not want to restrict these things, but a commit > that doesn't discuss this at all is not okay. Sorry. So it seems you're not NAKing the use of splat_input_operand, but just that it needs more explanation in the git log entry, correct? Yes, input_operand accepts a lot more things than splat_input_operand does, but the multiple define_insns this define_expand feeds, uses gpc_reg_operand, memory_operand and splat_input_operand for their operands[1] operand (splat_input_operand accepts reg and mem too), so it seems to match better what the patterns will be accepting and I always thought that using predicates that more accurately reflect what the define_insns expect/accept lead to better code gen. Mike, was it just an oversight to not use splat_input_operand for the vsx_splat_ expander or was input_operand a conscious decision? If input_operand was used purposely, then we can just fall back to the s/op1/operands[1]/ change which we already know fixes the bug. Peter
Re: [PATCH V2] rs6000: Don't allow immediate value in the vsx_splat pattern [PR113950]
Hi! On Tue, Feb 27, 2024 at 02:02:38AM +0530, jeevitha wrote: > There is no immediate value splatting instruction in Power. Currently, those > values need to be stored in a register or memory. To address this issue, I > have updated the predicate for the second operand in vsx_splat to > splat_input_operand and corrected the assignment of op1 to operands[1]. > These changes ensure that operand1 is stored in a register. input_operand allows a lot of things that splat_input_operand does not, not just immediate operands. NAK. (For example, *all* memory is okay for input_operand, always). I'm not saying we do not want to restrict these things, but a commit that doesn't discuss this at all is not okay. Sorry. Segher
