Explicitly backup and restore for each intrinsic just the same as we did for CALL in this patch.

I can't have the data to prove how good we use LCM/PRE of mode switching but I trust it.

Since the the LCM/PRE is the key optimization method of VSETVL PASS which is doing good job on VSETVL instruction optimizations.

I don't we should give up LCM/PRE chance then just backup and restore for each intrinsic bindly.
 



juzhe.zhong@rivai.ai
 
From: Robin Dapp
Date: 2023-07-26 21:46
To: juzhe.zhong; Li, Pan2
CC: rdapp.gcc; Kito Cheng; gcc-patches@gcc.gnu.org; Wang, Yanzhang
Subject: Re: [PATCH v7] RISC-V: Support CALL for RVV floating-point dynamic rounding
> current llvm didn't do any pre optimization.  They always
> backup+restore for each rounding mode intrinsic
 
I see.  There is still the option of lazily restoring the
(entry) FRM before a function call but not read the FRM
after every call.  Do we have any data on how good or bad the
mode-switching LCM works when we explicitly backup and restore
for each intrinsic?
 
Regards
Robin