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panfrost/midgard: Reduce fmax(a, 0.0) to fmov.pos

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This will allow us to copyprop away the move and eliminate the
instruction entirely.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
This commit is contained in:
Alyssa Rosenzweig
2019-04-24 23:42:30 +00:00
parent 295536d47a
commit 7bc91b487b
1 changed files with 33 additions and 3 deletions
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src/gallium/drivers/panfrost/midgard/midgard_compile.c
+33 -3
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@@ -1082,6 +1082,20 @@ emit_indirect_offset(compiler_context *ctx, nir_src *src)
op = midgard_alu_op_##_op; \
break;
static bool
nir_is_fzero_constant(nir_src src)
{
if (!nir_src_is_const(src))
return false;
for (unsigned c = 0; c < nir_src_num_components(src); ++c) {
if (nir_src_comp_as_float(src, c) != 0.0)
return false;
}
return true;
}
static void
emit_alu(compiler_context *ctx, nir_alu_instr *instr)
{
@@ -1245,13 +1259,29 @@ emit_alu(compiler_context *ctx, nir_alu_instr *instr)
return;
}
/* Midgard can perform certain modifiers on output ofa n ALU op */
midgard_outmod outmod =
instr->dest.saturate ? midgard_outmod_sat : midgard_outmod_none;
/* fmax(a, 0.0) can turn into a .pos modifier as an optimization */
if (instr->op == nir_op_fmax) {
if (nir_is_fzero_constant(instr->src[0].src)) {
op = midgard_alu_op_fmov;
nr_inputs = 1;
outmod = midgard_outmod_pos;
instr->src[0] = instr->src[1];
} else if (nir_is_fzero_constant(instr->src[1].src)) {
op = midgard_alu_op_fmov;
nr_inputs = 1;
outmod = midgard_outmod_pos;
}
}
/* Fetch unit, quirks, etc information */
unsigned opcode_props = alu_opcode_props[op].props;
bool quirk_flipped_r24 = opcode_props & QUIRK_FLIPPED_R24;
/* Initialise fields common between scalar/vector instructions */
midgard_outmod outmod = instr->dest.saturate ? midgard_outmod_sat : midgard_outmod_none;
/* src0 will always exist afaik, but src1 will not for 1-argument
* instructions. The latter can only be fetched if the instruction
* needs it, or else we may segfault. */