i965: Convert reloc.target_handle into an index for I915_EXEC_HANDLE_LUT

Based on a patch by Chris Wilson (who also wrote this commit message).

Passing the index of the target buffer via the reloc.target_handle is
marginally more efficient for the kernel (it can avoid some allocations,
and can use a direct lookup rather than a hash or search). It is also
useful for ourselves as we can use the index into our exec_bos for other
tasks.

v2: Only enable HANDLE_LUT if we can use BATCH_FIRST and thereby avoid
a post-processing loop to fixup the relocations.
v3: Move kernel probing from context creation to screen init.
Use batch->use_exec_lut as it more descriptive of what's going on (Daniel)
v4: Kernel features already exists, use it for BATCH_FIRST
Rename locals to preserve current flavouring
v5: Squash in "always insert batch bo first"
v6: (by Ken) Split out BATCH_FIRST from HANDLE_LUT.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
index d4ffbdac8a1..6e53bb19db5 100644
--- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
+++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
@@ -667,7 +667,7 @@ do_flush_locked(struct brw_context *brw, int in_fence_fd, int *out_fence_fd)
          entry->relocs_ptr = (uintptr_t) batch->relocs;
 
          if (batch->use_batch_first) {
-            flags |= I915_EXEC_BATCH_FIRST;
+            flags |= I915_EXEC_BATCH_FIRST | I915_EXEC_HANDLE_LUT;
          } else {
             /* Move the batch to the end of the validation list */
             struct drm_i915_gem_exec_object2 tmp;
@@ -821,7 +821,7 @@ brw_emit_reloc(struct intel_batchbuffer *batch, uint32_t batch_offset,
       (struct drm_i915_gem_relocation_entry) {
          .offset = batch_offset,
          .delta = target_offset,
-         .target_handle = target->gem_handle,
+         .target_handle = batch->use_batch_first ? index : target->gem_handle,
          .presumed_offset = entry->offset,
       };