Quoting Arnd Bergmann (2021-01-02 11:23:20)
On Wed, Dec 30, 2020 at 4:56 PM Chris Wilson chris@chris-wilson.co.uk wrote:
Quoting Arnd Bergmann (2020-12-30 15:39:14)
From: Arnd Bergmann arnd@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
Ah right, I misread the warning then.
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?
I suspect what is going on is that clang once again warns because it performs more code checks before dead-code elimination than gcc does. The warning is for the __const_hweight64() case, which is not actually used here because the input is not a compile-time constant.
So hweight_long?
That seems to work, I'll send a new version with that.
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); }
Fine with me as well. If you prefer that way, I'll let you handle that.
While we wait for a generic hweight(), lets use hweight_long() here. -Chris