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iter_div_u64_rem is used in the x86-64 vdso, which cannot call other
kernel code. For this case, provide the always_inlined version,
__iter_div_u64_rem.
Signed-off-by: Jeremy Fitzhardinge <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
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We have a few instances of the open-coded iterative div/mod loop, used
when we don't expcet the dividend to be much bigger than the divisor.
Unfortunately modern gcc's have the tendency to strength "reduce" this
into a full mod operation, which isn't necessarily any faster, and
even if it were, doesn't exist if gcc implements it in libgcc.
The workaround is to put a dummy asm statement in the loop to prevent
gcc from performing the transformation.
This patch creates a single implementation of this loop, and uses it
to replace the open-coded versions I know about.
Signed-off-by: Jeremy Fitzhardinge <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: john stultz <[email protected]>
Cc: Segher Boessenkool <[email protected]>
Cc: Christian Kujau <[email protected]>
Cc: Robert Hancock <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
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Rename div64_64 to div64_u64 to make it consistent with the other divide
functions, so it clearly includes the type of the divide. Move its definition
to math64.h as currently no architecture overrides the generic implementation.
They can still override it of course, but the duplicated declarations are
avoided.
Signed-off-by: Roman Zippel <[email protected]>
Cc: Avi Kivity <[email protected]>
Cc: Russell King <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: David Howells <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Patrick McHardy <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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The current do_div doesn't explicitly say that it's unsigned and the signed
counterpart is missing, which is e.g. needed when dealing with time values.
This introduces 64bit signed/unsigned divide functions which also attempts to
cleanup the somewhat awkward calling API, which often requires the use of
temporary variables for the dividend. To avoid the need for temporary
variables everywhere for the remainder, each divide variant also provides a
version which doesn't return the remainder.
Each architecture can now provide optimized versions of these function,
otherwise generic fallback implementations will be used.
As an example I provided an alternative for the current x86 divide, which
avoids the asm casts and using an union allows gcc to generate better code.
It also avoids the upper divde in a few more cases, where the result is known
(i.e. upper quotient is zero).
Signed-off-by: Roman Zippel <[email protected]>
Cc: john stultz <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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