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@xxxxxxx> 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 https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=246457 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 pure guesswork. Signed-off-by: George Spelvin <lkml@xxxxxxx> --- arch/s390/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index ed554b09eb3f..43e6dc677f7d 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -372,6 +372,7 @@ endchoice config 64BIT def_bool y + select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 70000 && HAVE_MARCH_ZEC12_FEATURES || CC_IS_CLANG config COMPAT def_bool y -- 2.20.1
