| Message ID | 20201230153928.456260-1-arnd@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | i915: fix shift warning | expand |
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 > 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 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
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. Arnd _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
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 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 0a3ee4f9dc0a..ca32fa0d6a57 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1624,7 +1624,7 @@ tgl_revids_get(struct drm_i915_private *dev_priv) unsigned int first__ = (first); \ unsigned int count__ = (count); \ ((gt)->info.engine_mask & \ - GENMASK(first__ + count__ - 1, first__)) >> first__; \ + GENMASK_ULL(first__ + count__ - 1, first__)) >> first__; \ }) #define VDBOX_MASK(gt) \ ENGINE_INSTANCES_MASK(gt, VCS0, I915_MAX_VCS)