[Mesa-dev] [PATCH 0/2] i965/vec4: Change SEL and MOV types as needed to propagate source modifiers

[Alejandro Piñeiro]

On the review of the patch "i965/nir/vec4: fill the type of the dst
and src when loading an uniform" Jason Ekstrand suggested to change
the optimization pass in order to allow the copy propagation with
MOVs even if there is a type mismatch, as was done on the fs path,
instead of fixing the type for MOV instructions.[1]

So using commit 472ef9 as reference I implemented the equivalent
for the vec4 case. But that only worked if it was the current
instruction the MOV with default types. It didn't fixed the shader-db
instruction count regression I was working on, that was when it was
the from instruction the MOV with default types. Or in other words,
it didn't cover this case:

   1: mov vgrf1.0:UD, u0.xyzw:UD
   2: add vgrf2.0:F, vgrf0.xyzw:F, -vgrf1.xyzw:F

So I extended the same idea by checking too against the from
instruction. In order to do that, I needed to also track
the vec4_instructions on the copy_entry struct.

Submitting two patches because I think that it will be easier
to review in this way. But if this solutions is approved, I
think that it could be better to push them squashed on just
one patch.

Shader-db results for vec4 programs on Haswell:
total instructions in shared programs: 1746280 -> 1732159 (-0.81%)
instructions in affected programs:     760595 -> 746474 (-1.86%)
helped:                                6132
HURT:                                  0
GAINED:                                0
LOST:                                  0


[1] http://lists.freedesktop.org/archives/mesa-dev/2015-September/094555.html

Alejandro Piñeiro (2):
  i965/vec4: Change types as needed to propagate source modifiers using
    current instruction
  i965/vec4: Change types as needed to propagate source modifiers using
    from instruction

 .../drivers/dri/i965/brw_vec4_copy_propagation.cpp | 45 ++++++++++++++++++++--
 1 file changed, 41 insertions(+), 4 deletions(-)

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2.1.4