[Intel-gfx] [PATCH] i915: fix shift warning

[Chris Wilson]

Quoting Arnd Bergmann (2020-12-30 15:39:14)
> From: Arnd Bergmann <arnd at arndb.de>
> 
> Randconfig builds on 32-bit machines show lots of warnings for
> the i915 driver for incorrect bit masks like:

mask is a u8.

VCS0 is 2, I915_MAX_VCS 4

(u8 & GENMASK(5, 2)) >> 2

> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2584:9: error: shift count >= width of type [-Werror,-Wshift-count-overflow]
>         return hweight64(VDBOX_MASK(&i915->gt));
>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/asm-generic/bitops/const_hweight.h:29:49: note: expanded from macro 'hweight64'
>  #define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w))

So it's upset by hweight64() on the unsigned long?
So hweight_long?

Or use a cast, hweight8((intel_engine_mask_t)VDMASK())?

static __always_inline int engine_count(intel_engine_mask_t mask)
{
	return sizeof(mask) == 1 ? hweight8(mask) :
		sizeof(mask) == 2 ? hweight16(mask) :
		sizeof(mask) == 4 ? hweight32(mask) :
		hweight64(mask);
}
-Chris