Kyrylo Tkachov <ktkac...@nvidia.com> writes: >> On 9 Sep 2024, at 11:06, Tamar Christina <tamar.christ...@arm.com> wrote: >> >> External email: Use caution opening links or attachments >> >> >>> -----Original Message----- >>> From: Richard Sandiford <richard.sandif...@arm.com> >>> Sent: Monday, September 9, 2024 9:29 AM >>> To: Tamar Christina <tamar.christ...@arm.com> >>> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; Richard Earnshaw >>> <richard.earns...@arm.com>; Marcus Shawcroft >>> <marcus.shawcr...@arm.com>; ktkac...@gcc.gnu.org >>> Subject: Re: [PATCH 4/4]AArch64: Define VECTOR_STORE_FLAG_VALUE. >>> >>> Tamar Christina <tamar.christ...@arm.com> writes: >>>> Hi All, >>>> >>>> This defines VECTOR_STORE_FLAG_VALUE to CONST1_RTX for AArch64 >>>> so we simplify vector comparisons in AArch64. >>>> >>>> With this enabled >>>> >>>> res: >>>> movi v0.4s, 0 >>>> cmeq v0.4s, v0.4s, v0.4s >>>> ret >>>> >>>> is simplified to: >>>> >>>> res: >>>> mvni v0.4s, 0 >>>> ret >>>> >>>> NOTE: I don't really like the testcase as it depends on an >>>> uninitialised value to hide the constant from GIMPLE. >>>> >>>> Happy to go with something else if there are any suggestions. >>>> I thought about an RTL testcase, but those seem painful. >>> >>> Like you say, I think an RTL testcase would be better. Could you use >>> the attached (for gcc.dg/rtl/aarch64)? >>> >> >> Thanks, do you have any tips for writing these? If there a way to dump a >> skeleton like with the gimple tests?
TBH I just take one I wrote earlier that looks relatively close, then adapt it. They're not something I could easily write from scratch. > As a tangent, I wonder if the RTL dump logic can be extended to have a > dump-for-rtl-testcase mode, under the reasoning that creating RTL test cases > for ICE fixes is a common action. It could even be used in the EMERGENCY DUMP > case when dumping during an ICE. Yeah, perhaps. But I think there is an advantage in writing the test by hand, to make sure that everything in the test is necessary and relatively future-proof. Often, the reason for using an RTL testcase is that it isn't easy to create a minimal RTL reproducer from gimple. Most EMERGENCY DUMPs from non-RTL testcases are therefore likely to contain stuff that isn't directly relevant. Thanks, Richard
