i965/fs: Rework the fs_visitor LOAD_PAYLOAD instruction

The newly reworked instruction is far more straightforward than the
original.  Before, the LOAD_PAYLOAD instruction was lowered by a the
complicated and broken-by-design pile of heuristics to try and guess
force_writemask_all, exec_size, and a number of other factors on the
sources.

Instead, we use the header_size on the instruction to denote which sources
are "header sources".  Header sources are required to be a single physical
hardware register that is copied verbatim.  The registers that follow are
considered the actual payload registers and have a width that correspond's
to the LOAD_PAYLOAD's exec_size and are treated as being per-channel.  This
gives us a fairly straightforward lowering:

 1) All header sources are copied directly using force_writemask_all and,
    since they are guaranteed to be a single register, there are no
    force_sechalf issues.

 2) All non-header sources are copied using the exact same force_sechalf
    and force_writemask_all modifiers as the LOAD_PAYLOAD operation itself.

 3) In order to accommodate older gens that need interleaved colors,
    lower_load_payload detects when the destination is a COMPR4 register
    and automatically interleaves the non-header sources.  The
    lower_load_payload pass does the right thing here regardless of whether
    or not the hardware actually supports COMPR4.

This patch commit itself is made up of a bunch of smaller changes squashed
together.  Individual change descriptions follow:

i965/fs: Rework fs_visitor::LOAD_PAYLOAD

   We rework LOAD_PAYLOAD to verify that all of the sources that count as
   headers are, indeed, exactly one register and that all of the non-header
   sources match the destination width.  We then take the exec_size for
   LOAD_PAYLOAD directly from the destination width.

i965/fs: Make destinations of load_payload have the appropreate width

i965/fs: Rework fs_visitor::lower_load_payload

   v2: Don't allow the saturate flag on LOAD_PAYLOAD instructions

i965/fs_cse: Support the new-style LOAD_PAYLOAD

i965/fs_inst::is_copy_payload: Support the new-style LOAD_PAYLOAD

i965/fs: Simplify setup_color_payload

   Previously, setup_color_payload was a a big helper function that did a
   lot of gen-specific special casing for setting up the color sources of
   the LOAD_PAYLOAD instruction.  Now that lower_load_payload is much more
   sane, most of that complexity isn't needed anymore.  Instead, we can do
   a simple fixup pass for color clamps and then just stash sources
   directly in the LOAD_PAYLOAD.  We can trust lower_load_payload to do the
   right thing with respect to COMPR4.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index 30cefe4..1d7de2e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -394,8 +394,8 @@ public:
    bool optimize_frontfacing_ternary(nir_alu_instr *instr,
                                      const fs_reg &result);
 
-   int setup_color_payload(fs_reg *dst, fs_reg color, unsigned components,
-                           bool use_2nd_half);
+   void setup_color_payload(fs_reg *dst, fs_reg color, unsigned components,
+                            unsigned exec_size, bool use_2nd_half);
    void emit_alpha_test();
    fs_inst *emit_single_fb_write(fs_reg color1, fs_reg color2,
                                  fs_reg src0_alpha, unsigned components,