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x86/div64: Fix addition of large constants in mul_u64_add_u64_div_u64()

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Adding constants over 2^31 fails to compile because the ADD instruction only
supports 32bit signed immediates.

Replace the "irm" constraint with "erm" so that the compiler loads large
constants into a register.

Found by a patch to drivers/iio/frequency/ad9910.c

  [ bp: Massage commit message. ]

Fixes: 6480241f31 ("lib: add mul_u64_add_u64_div_u64() and mul_u64_u64_div_u64_roundup()")
Signed-off-by: David Laight <david.laight.linux@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: H. Peter Anvin <hpa@zytor.com>
Link: https://patch.msgid.link/20260803094702.3852-2-david.laight.linux@gmail.com
This commit is contained in:
David Laight 2026-08-03 10:47:01 +01:00 committed by Borislav Petkov (AMD)
parent 5a5d26f2cf
commit f65d38155a
1 changed files with 1 additions and 1 deletions
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2
arch/x86/include/asm/div64.h
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@ -111,7 +111,7 @@ static inline u64 mul_u64_add_u64_div_u64(u64 rax, u64 mul, u64 add, u64 div)
if (!statically_true(!add))
asm ("addq %[add], %[lo]; adcq $0, %[hi]" :
[lo] "+r" (rax), [hi] "+r" (rdx) : [add] "irm" (add));
[lo] "+r" (rax), [hi] "+r" (rdx) : [add] "erm" (add));
asm ("divq %[div]" : "+a" (rax), "+d" (rdx) : [div] "rm" (div));