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nir/scale_fdiv: handle fp16 fdiv

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Not strictly scaling, but we upcast fo fp32, do the fdiv there and cast
back again.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34053>
This commit is contained in:
Karol Herbst 2025-03-13 17:44:28 +01:00 • committed by Marge Bot
parent aa5a981b83
commit 33fb1eca3e
1 changed files with 37 additions and 20 deletions
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57
src/compiler/nir/nir_scale_fdiv.c
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@ -29,33 +29,50 @@
static bool
nir_scale_fdiv_instr(nir_builder *b, nir_alu_instr *alu, UNUSED void *_data)
{
if (alu->op != nir_op_fdiv || alu->src[0].src.ssa->bit_size != 32)
if (alu->op != nir_op_fdiv)
return false;
b->cursor = nir_before_instr(&alu->instr);
switch (alu->src[0].src.ssa->bit_size) {
case 16: {
b->cursor = nir_before_instr(&alu->instr);
nir_def *orig_a = nir_ssa_for_alu_src(b, alu, 0);
nir_def *orig_b = nir_ssa_for_alu_src(b, alu, 1);
nir_def *fabs = nir_fabs(b, orig_b);
nir_def *big = nir_fgt_imm(b, fabs, uif(0x7e800000));
nir_def *small = nir_flt_imm(b, fabs, uif(0x00800000));
nir_def *src0 = nir_ssa_for_alu_src(b, alu, 0);
nir_def *src1 = nir_ssa_for_alu_src(b, alu, 1);
nir_def *scaled_down_a = nir_fmul_imm(b, orig_a, 0.25);
nir_def *scaled_down_b = nir_fmul_imm(b, orig_b, 0.25);
nir_def *scaled_up_a = nir_fmul_imm(b, orig_a, 16777216.0);
nir_def *scaled_up_b = nir_fmul_imm(b, orig_b, 16777216.0);
nir_def *new_div = nir_fdiv(b, nir_f2f32(b, src0), nir_f2f32(b, src1));
new_div = nir_f2f16(b, new_div);
nir_def *final_a =
nir_bcsel(b, big, scaled_down_a,
(nir_bcsel(b, small, scaled_up_a, orig_a)));
nir_def *final_b =
nir_bcsel(b, big, scaled_down_b,
(nir_bcsel(b, small, scaled_up_b, orig_b)));
nir_def_rewrite_uses(&alu->def, new_div);
return true;
}
case 32: {
b->cursor = nir_before_instr(&alu->instr);
nir_def *new_div = nir_fdiv(b, final_a, final_b);
nir_def_rewrite_uses(&alu->def, new_div);
nir_def *orig_a = nir_ssa_for_alu_src(b, alu, 0);
nir_def *orig_b = nir_ssa_for_alu_src(b, alu, 1);
nir_def *fabs = nir_fabs(b, orig_b);
nir_def *big = nir_fgt_imm(b, fabs, uif(0x7e800000));
nir_def *small = nir_flt_imm(b, fabs, uif(0x00800000));
return true;
nir_def *scaled_down_a = nir_fmul_imm(b, orig_a, 0.25);
nir_def *scaled_down_b = nir_fmul_imm(b, orig_b, 0.25);
nir_def *scaled_up_a = nir_fmul_imm(b, orig_a, 16777216.0);
nir_def *scaled_up_b = nir_fmul_imm(b, orig_b, 16777216.0);
nir_def *final_a =
nir_bcsel(b, big, scaled_down_a,
(nir_bcsel(b, small, scaled_up_a, orig_a)));
nir_def *final_b =
nir_bcsel(b, big, scaled_down_b,
(nir_bcsel(b, small, scaled_up_b, orig_b)));
nir_def *new_div = nir_fdiv(b, final_a, final_b);
nir_def_rewrite_uses(&alu->def, new_div);
return true;
}
default:
return false;
}
}
/** Scale both sides of an fdiv if needed to prevent denorm flushing