ir3/nir: Add a new pass 'ir3_nir_lower_io_offsets'

This NIR->NIR pass implements offset computations that are currently
done on the IR3 backend compiler, to give NIR a better chance of
optimizing them.

For now, it supports lowering the dword-offset computation for SSBO
instructions. It will take an SSBO intrinsic and replace it with the
new ir3-specific version that adds an extra source. That source will
hold the SSA value resulting from inserting a division by 4 (an SHR op)
of the original byte-offset source already provided by NIR in one of
the intrinsic sources.

Note that on a6xx the original byte-offset is not needed, so we could
potentially replace that source instead of adding a new one. But to
keep things simple and consistent we always add the new source and
a6xx will just ignore the original one.

Reviewed-by: Rob Clark <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/freedreno/ir3/ir3_nir.h b/src/freedreno/ir3/ir3_nir.h
index 74201d34160..7983b74af2c 100644
--- a/src/freedreno/ir3/ir3_nir.h
+++ b/src/freedreno/ir3/ir3_nir.h
@@ -36,6 +36,7 @@ void ir3_nir_scan_driver_consts(nir_shader *shader, struct ir3_driver_const_layo
 
 bool ir3_nir_apply_trig_workarounds(nir_shader *shader);
 bool ir3_nir_lower_tg4_to_tex(nir_shader *shader);
+bool ir3_nir_lower_io_offsets(nir_shader *shader);
 
 const nir_shader_compiler_options * ir3_get_compiler_options(struct ir3_compiler *compiler);
 bool ir3_key_lowers_nir(const struct ir3_shader_key *key);