drm/i915: tweak gen6_for_{each_pde, all_pdes} macros

Gen8 versions of these macros were updated a few months ago
(e8ebd8e drm/i915: eliminate 'temp' in gen8_for_each macros)
originally because at least one iterator could generate an
out of bounds access, but also because eliminating the 'temp'
parameter generated smaller and faster code.

Matthew Auld recently noticed the same problem with the gen6
versions and provided a patch
https://lists.freedesktop.org/archives/intel-gfx/2016-June/099334.html
but while we're changing these, we might as well make them as
much like the gen8 versions as possible, including the style
of using "&& (..., true)" rather than ": (..., 1) : 0", and
of course eliminating the redundant 'temp'.

Furthermore, the "all_pdes" version is only used in one place,
so we can improve code efficiency by changing both the macro
parameters and the calling code to reduce extra dereferences.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466793466-23500-1-git-send-email-david.s.gordon@intel.com

1 files changed, 20 insertions, 20 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 163b564fb87d..aa5f31d1c2ed 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -390,27 +390,27 @@ struct i915_hw_ppgtt {
 	void (*debug_dump)(struct i915_hw_ppgtt *ppgtt, struct seq_file *m);
 };
 
-/* For each pde iterates over every pde between from start until start + length.
- * If start, and start+length are not perfectly divisible, the macro will round
- * down, and up as needed. The macro modifies pde, start, and length. Dev is
- * only used to differentiate shift values. Temp is temp.  On gen6/7, start = 0,
- * and length = 2G effectively iterates over every PDE in the system.
- *
- * XXX: temp is not actually needed, but it saves doing the ALIGN operation.
+/*
+ * gen6_for_each_pde() iterates over every pde from start until start+length.
+ * If start and start+length are not perfectly divisible, the macro will round
+ * down and up as needed. Start=0 and length=2G effectively iterates over
+ * every PDE in the system. The macro modifies ALL its parameters except 'pd',
+ * so each of the other parameters should preferably be a simple variable, or
+ * at most an lvalue with no side-effects!
  */
-#define gen6_for_each_pde(pt, pd, start, length, temp, iter) \
-	for (iter = gen6_pde_index(start); \
-	     length > 0 && iter < I915_PDES ? \
-			(pt = (pd)->page_table[iter]), 1 : 0; \
-	     iter++, \
-	     temp = ALIGN(start+1, 1 << GEN6_PDE_SHIFT) - start, \
-	     temp = min_t(unsigned, temp, length), \
-	     start += temp, length -= temp)
-
-#define gen6_for_all_pdes(pt, ppgtt, iter)  \
-	for (iter = 0;		\
-	     pt = ppgtt->pd.page_table[iter], iter < I915_PDES;	\
-	     iter++)
+#define gen6_for_each_pde(pt, pd, start, length, iter)			\
+	for (iter = gen6_pde_index(start);				\
+	     length > 0 && iter < I915_PDES &&				\
+		(pt = (pd)->page_table[iter], true);			\
+	     ({ u32 temp = ALIGN(start+1, 1 << GEN6_PDE_SHIFT);		\
+		    temp = min(temp - start, length);			\
+		    start += temp, length -= temp; }), ++iter)
+
+#define gen6_for_all_pdes(pt, pd, iter)					\
+	for (iter = 0;							\
+	     iter < I915_PDES &&					\
+		(pt = (pd)->page_table[iter], true);			\
+	     ++iter)
 
 static inline uint32_t i915_pte_index(uint64_t address, uint32_t pde_shift)
 {