[Mesa-dev] [PATCH 0/6] nir: Implement a load-combine pass
Eduardo Lima Mitev
elima at igalia.com
Thu Apr 14 16:52:30 UTC 2016
This is a series adding a new NIR pass that will combine redundant SSBO, shared variable and image load instructions. It is based on a previous series that Iago Toral  sent a few months ago, which I have updated to account for changes in NIR since then, and also added support for shared variables and image load/store.
Currently, the emitted load instructions for these types of variables are highly redundant. For example, assuming 'value' is an SSBO float, doing:
float next = value + 1.0;
float prev = value - 1.0;
will generate two redundant load_ssbo instructions. The extreme case of this is:
mat4 mult = ssbo_mat4 * ssbo_mat4;
which will spwan 16 load_ssbo instructions.
Compute shader's shared variables and image loads (from ARB_image_load_store) suffer from the same problem. This pass coaleses the redundant loads, and is also able to combine a load with a previous store to the same address.
I'm still working on a piglit test series that tied up the different corner cases, but it doesn't hurt to get a few eyes on this already. The WIP piglit branch is at: https://github.com/Igalia/piglit/commits/nir-opt-load-combine-rc1
You can see there a test example for the matrix multiplication cases: https://github.com/Igalia/piglit/commit/b7ea6d2553891c7eec993c39352a10925ebcefbc. This pass is able to reduce the emitted instructions from 210 to 134 (~64%), comparing to Mesa master.
No piglit or dEQP-GLES31 regressions observed.
Eduardo Lima Mitev (3):
nir/opt_load_combine: Extend the pass to include shared variables
nir/opt_load_combine: Extend the pass to include image load/store
Iago Toral (3):
nir: add a load-combine pass
nir/load_combine: expand the pass to support load-after-store
i965: use the load-combine pass
src/compiler/Makefile.sources | 1 +
src/compiler/nir/nir.h | 2 +
src/compiler/nir/nir_opt_load_combine.c | 807 ++++++++++++++++++++++++++++++++
src/mesa/drivers/dri/i965/brw_nir.c | 1 +
4 files changed, 811 insertions(+)
create mode 100644 src/compiler/nir/nir_opt_load_combine.c
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