ptr_unpack_bits() is a function-like macro, as such it is meant to be
replaceable by a function. In this case, we should be passing in the
out-param as a pointer.
Bizarrely this does affect code generation:
function old new delta
i915_gem_object_pin_map 409 389 -20
An improvement(?) in this case, but one can't help wonder what
strict-aliasing optimisations we are preventing.
The generated code looks identical in using ptr_unpack_bits (no extra
motions to stack, the pointer and bits appear to be kept in registers),
the difference appears to be code ordering and with a reorder it is able
to use smaller forward jumps.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 2 +-
drivers/gpu/drm/i915/i915_utils.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0f8046e0a63c..a0186a5df05b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2631,7 +2631,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
}
GEM_BUG_ON(!obj->mm.pages);
- ptr = ptr_unpack_bits(obj->mm.mapping, has_type);
+ ptr = ptr_unpack_bits(obj->mm.mapping, &has_type);
if (ptr && has_type != type) {
if (pinned) {
ret = -EBUSY;
diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
index c5455d36b617..aca11aad5da7 100644
--- a/drivers/gpu/drm/i915/i915_utils.h
+++ b/drivers/gpu/drm/i915/i915_utils.h
@@ -77,7 +77,7 @@
#define ptr_unpack_bits(ptr, bits) ({ \
unsigned long __v = (unsigned long)(ptr); \
- (bits) = __v & ~PAGE_MASK; \
+ *(bits) = __v & ~PAGE_MASK; \
(typeof(ptr))(__v & PAGE_MASK); \
})
--
2.11.0
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