tree a468c5bb0428be35da5200af5c3aa44dde163b81
parent 72d931046030beb2d13dad6d205be0e228618432
author Linus Torvalds <torvalds@linux-foundation.org> 1410632643 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1410632643 -0700

Make hash_64() use a 64-bit multiply when appropriate

The hash_64() function historically does the multiply by the
GOLDEN_RATIO_PRIME_64 number with explicit shifts and adds, because
unlike the 32-bit case, gcc seems unable to turn the constant multiply
into the more appropriate shift and adds when required.

However, that means that we generate those shifts and adds even when the
architecture has a fast multiplier, and could just do it better in
hardware.

Use the now-cleaned-up CONFIG_ARCH_HAS_FAST_MULTIPLIER (together with
"is it a 64-bit architecture") to decide whether to use an integer
multiply or the explicit sequence of shift/add instructions.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>