From: "Maciej W. Rozycki via Libc-alpha" <libc-alpha@sourceware.org>
To: Alistair Francis <alistair23@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
Alistair Francis <alistair.francis@wdc.com>
Subject: Re: [PATCH v2 10/18] RISC-V: Hard float support for 32-bit
Date: Sun, 12 Jul 2020 23:10:06 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.2007122157540.24175@redsun52.ssa.fujisawa.hgst.com> (raw)
In-Reply-To: <CAKmqyKN=xbr1+ECWqV3f2wbc-TeGfKS+csV7oi+NwSz=kndUAQ@mail.gmail.com>
On Sun, 12 Jul 2020, Alistair Francis wrote:
> > I don't think there is a simple alternative available for RV32 that would
> > be worth keeping together with the RV64 variant. Did I miss anything?
> > What instruction(s) do you have in mind?
>
> Something like this for the generic RISC-V lround:
>
> long int
> __lroundf (float x)
> {
> #if __WORDSIZE == 64
> int64_t res;
> asm ("fcvt.l.s %0, %1, rmm" : "=r" (res) : "f" (x));
> #else
> int32_t res;
> asm ("fcvt.w.s %0, %1, rmm" : "=r" (res) : "f" (x));
> #endif
> return res;
> }
>
> I'm not sure if it's clearer, but for some of the more complex
> functions (roundeven for example) it might be easier.
>
> It also means if there is a bug fixed in one it'll end up fixed for both.
Ah, you mean the `float' to `long int' conversion functions, necessarily
ABI-specific due to the changing width of the latter data type. Well, I
meant the operations involving FCVT.L.D/FCVT.D.L. I can see no RISC-V
solution for them that would surpass the generic implementation.
As far as your example above is concerned if we decided to merge the
files at all, I would reduce it to:
#if __WORDSIZE == 64
# define OP "fcvt.l.s"
#elif __WORDSIZE == 32
# define OP "fcvt.w.s"
#else
# error Unsupported
#endif
long int
__lroundf (float x)
{
long int res;
asm (OP "\t%0, %1, rmm" : "=r" (res) : "f" (x));
return res;
}
or suchlike (I'm not sure if there's any gain here from `res' having an
explicit-width data type). Likewise with the rest.
Maciej
next prev parent reply other threads:[~2020-07-12 22:10 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 16:25 [PATCH v2 00/18] glibc port for 32-bit RISC-V (RV32) Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 01/18] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64 Alistair Francis via Libc-alpha
2020-07-07 22:06 ` Maciej W. Rozycki via Libc-alpha
2020-07-10 15:27 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 02/18] RISC-V: Define __NR_* as __NR_*_time64/64 for 32-bit Alistair Francis via Libc-alpha
2020-07-08 0:09 ` Maciej W. Rozycki via Libc-alpha
2020-07-08 17:08 ` Adhemerval Zanella via Libc-alpha
2020-07-09 17:14 ` Alistair Francis via Libc-alpha
2020-07-16 0:23 ` Maciej W. Rozycki via Libc-alpha
2020-07-09 17:10 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 03/18] RISC-V: Add support for 32-bit vDSO calls Alistair Francis via Libc-alpha
2020-07-08 1:01 ` Maciej W. Rozycki via Libc-alpha
2020-07-08 18:17 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 04/18] RISC-V: Support dynamic loader for the 32-bit Alistair Francis via Libc-alpha
2020-07-08 1:35 ` Maciej W. Rozycki via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 05/18] RISC-V: Add path of library directories " Alistair Francis via Libc-alpha
2020-07-08 18:42 ` Maciej W. Rozycki via Libc-alpha
2020-07-09 17:03 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 06/18] RISC-V: Add arch-syscall.h for RV32 Alistair Francis via Libc-alpha
2020-07-08 19:33 ` Maciej W. Rozycki via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 07/18] RISC-V: nptl: update default pthread-offsets.h Alistair Francis via Libc-alpha
2020-07-09 0:14 ` Maciej W. Rozycki via Libc-alpha
2020-07-09 11:47 ` Adhemerval Zanella via Libc-alpha
2020-07-15 19:23 ` Maciej W. Rozycki via Libc-alpha
2020-08-10 17:34 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 08/18] riscv32: Add an architecture ipctypes.h Alistair Francis via Libc-alpha
2020-07-09 2:46 ` Maciej W. Rozycki via Libc-alpha
2020-07-09 11:36 ` Adhemerval Zanella via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 09/18] RISC-V: The ABI implementation for 32-bit Alistair Francis via Libc-alpha
2020-07-09 23:33 ` Maciej W. Rozycki via Libc-alpha
2020-07-10 16:45 ` Alistair Francis via Libc-alpha
2020-07-11 1:24 ` Maciej W. Rozycki via Libc-alpha
2020-08-10 21:29 ` Alistair Francis via Libc-alpha
2020-08-27 19:43 ` Adhemerval Zanella via Libc-alpha
2020-09-25 23:03 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 10/18] RISC-V: Hard float support " Alistair Francis via Libc-alpha
2020-07-11 0:49 ` Maciej W. Rozycki via Libc-alpha
2020-07-11 15:49 ` Alistair Francis via Libc-alpha
2020-07-11 22:13 ` Maciej W. Rozycki via Libc-alpha
2020-07-12 15:34 ` Alistair Francis via Libc-alpha
2020-07-12 22:10 ` Maciej W. Rozycki via Libc-alpha [this message]
2020-08-27 18:36 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 11/18] RISC-V: Add ABI lists Alistair Francis via Libc-alpha
2020-07-12 20:54 ` Maciej W. Rozycki via Libc-alpha
2020-07-13 16:14 ` Alistair Francis via Libc-alpha
2020-06-03 16:25 ` [PATCH v2 12/18] RISC-V: Add the RV32 libm-test-ulps Alistair Francis via Libc-alpha
2020-06-03 17:34 ` Joseph Myers
2020-06-05 4:01 ` Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 13/18] RISC-V: Fix llrint and llround missing exceptions on RV32 Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 14/18] RISC-V: Build Infastructure for 32-bit Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 15/18] riscv32: Specify the arch_minimum_kernel as 5.4 Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 16/18] RISC-V: Add rv32 path to RTLDLIST in ldd Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 17/18] Documentation for the RISC-V 32-bit port Alistair Francis via Libc-alpha
2020-06-03 16:26 ` [PATCH v2 18/18] Add RISC-V 32-bit target to build-many-glibcs.py Alistair Francis via Libc-alpha
2020-06-15 22:37 ` [PATCH v2 00/18] glibc port for 32-bit RISC-V (RV32) Alistair Francis via Libc-alpha
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