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agx: Only emit the used components of gl_FragCoord

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In case a shader only use gl_FragCoord.xy, this avoids wasting
coefficient registers for gl_FragCoord.zw which should be a small
optimization. It's also less work for DCE but I'm less worried about
that.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17198>
This commit is contained in:
Alyssa Rosenzweig 2022-08-07 16:25:13 -04:00
parent 17168162fb
commit 3712609ee3
1 changed files with 15 additions and 11 deletions
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26
src/asahi/compiler/agx_compile.c
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@ -522,21 +522,25 @@ agx_emit_load_ubo(agx_builder *b, agx_index dst, nir_intrinsic_instr *instr)
return NULL;
}
/*
* Emit code to generate gl_FragCoord. The xy components are calculated from
* special registers, whereas the zw components are interpolated varyings.
* Because interpolating varyings requires allocating coefficient registers that
* might not be used, we only emit code for components that are actually used.
*/
static void
agx_emit_load_frag_coord(agx_builder *b, agx_index *dests, nir_intrinsic_instr *instr)
{
/* xy */
for (unsigned i = 0; i < 2; ++i) {
dests[i] = agx_fadd(b, agx_convert(b, agx_immediate(AGX_CONVERT_U32_TO_F),
agx_get_sr(b, 32, AGX_SR_THREAD_POSITION_IN_GRID_X + i),
AGX_ROUND_RTE), agx_immediate_f(0.5f));
u_foreach_bit(i, nir_ssa_def_components_read(&instr->dest.ssa)) {
if (i < 2) {
dests[i] = agx_fadd(b, agx_convert(b, agx_immediate(AGX_CONVERT_U32_TO_F),
agx_get_sr(b, 32, AGX_SR_THREAD_POSITION_IN_GRID_X + i),
AGX_ROUND_RTE), agx_immediate_f(0.5f));
} else {
agx_index cf = agx_get_cf(b->shader, true, false, VARYING_SLOT_POS, i, 1);
dests[i] = agx_iter(b, cf, agx_null(), 1, false);
}
}
agx_index w = agx_get_cf(b->shader, true, false, VARYING_SLOT_POS, 3, 1);
agx_index z = agx_get_cf(b->shader, true, false, VARYING_SLOT_POS, 2, 1);
dests[2] = agx_iter(b, z, agx_null(), 1, false);
dests[3] = agx_iter(b, w, agx_null(), 1, false);
}
static agx_instr *