i965/eu: Refactor jump distance scaling to use a helper function.

Different generations of hardware measure jump distances in different
units.  Previously, every function that needed to set a jump target open
coded this scaling, or made a hardcoded assumption (i.e. just used 2).

Most functions start with the number of instructions to jump, and scale
up to the hardware-specific value.  So, I made the function match that.

Others start with a byte offset, and divide by a constant (8) to obtain
the jump distance.  This is actually 16 / 2 (the jump scale for Gen5-7).

v2: Make the helper a static inline defined in brw_eu.h, instead of
    an actual function in brw_eu_emit.c (as suggested by Matt).

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Chris Forbes <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_eu.h b/src/mesa/drivers/dri/i965/brw_eu.h
index 7efc02816c9..3e03ab82cc0 100644
--- a/src/mesa/drivers/dri/i965/brw_eu.h
+++ b/src/mesa/drivers/dri/i965/brw_eu.h
@@ -316,6 +316,26 @@ void brw_shader_time_add(struct brw_compile *p,
                          struct brw_reg payload,
                          uint32_t surf_index);
 
+/**
+ * Return the generation-specific jump distance scaling factor.
+ *
+ * Given the number of instructions to jump, we need to scale by
+ * some number to obtain the actual jump distance to program in an
+ * instruction.
+ */
+static inline unsigned
+brw_jump_scale(const struct brw_context *brw)
+{
+   /* Ironlake and later measure jump targets in 64-bit data chunks (in order
+    * (to support compaction), so each 128-bit instruction requires 2 chunks.
+    */
+   if (brw->gen >= 5)
+      return 2;
+
+   /* Gen4 simply uses the number of 128-bit instructions. */
+   return 1;
+}
+
 /* If/else/endif.  Works by manipulating the execution flags on each
  * channel.
  */