CONFIG_ARCH_SUPPORTS_INT128: Why not mips, s390, powerpc, and alpha?
lkml at sdf.org
Sat Mar 30 21:30:23 AEDT 2019
On Sat, 30 Mar 2019 at 09:43:47 +0100, Heiko Carstens wrote:
> It hasn't been enabled on s390 simply because at least I wasn't aware
> of this config option. Feel free to send a patch, otherwise I will
> enable this. Whatever you prefer.
> Thanks for pointing this out!
Here's a draft patch, but obviously it should be tested!
>From 6f3cc608c49dba33a38e81232a2fd46e8fa8dbcd Mon Sep 17 00:00:00 2001
From: George Spelvin <lkml at sdf.org>
Date: Sat, 30 Mar 2019 10:27:14 +0000
Subject: [PATCH] s390: Enable CONFIG_ARCH_SUPPORTS_INT128 on 64-bit builds
If a platform supports a 64x64->128-bit widening multiply,
that allows more efficient scaling of 64-bit values in various
parts of the kernel. GCC advertises __int128 support with the
__INT128__ #define, but we care about efficient inline
support, so this is a separate flag.
For s390, that was added on 24 March 2017 by
which is part of GCC 7.
It also only applies to TARGET_ARCH12, which I am guessing
corresponds to HAVE_MARCH_ZEC12_FEATURES. clang support is
Signed-off-by: George Spelvin <lkml at sdf.org>
arch/s390/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index ed554b09eb3f..43e6dc677f7d 100644
@@ -372,6 +372,7 @@ endchoice
+ select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 70000 && HAVE_MARCH_ZEC12_FEATURES || CC_IS_CLANG
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