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authorIago Toral Quiroga <[email protected]>2016-01-04 12:52:14 +0100
committerSamuel Iglesias Gonsálvez <[email protected]>2016-04-28 11:58:13 +0200
commit5fab3d178b7093b0f0e5e98f09052f401ac714ad (patch)
tree3cc50a18dd248b29714ddce24ebc5692ef9454bb /src/compiler
parent2ea3649c63f39f07b9cebda1ef0569b7347ada93 (diff)
nir/lower_double_ops: lower trunc()
At least i965 hardware does not have native support for truncating doubles. v2: - Simplified the implementation significantly. - Fixed the else branch, that was not doing what we wanted. Reviewed-by: Jason Ekstrand <[email protected]>
Diffstat (limited to 'src/compiler')
-rw-r--r--src/compiler/nir/nir.h1
-rw-r--r--src/compiler/nir/nir_lower_double_ops.c60
2 files changed, 61 insertions, 0 deletions
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index cbbf47e2570..4a49d6e1ac8 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2417,6 +2417,7 @@ typedef enum {
nir_lower_drcp = (1 << 0),
nir_lower_dsqrt = (1 << 1),
nir_lower_drsq = (1 << 2),
+ nir_lower_dtrunc = (1 << 3),
} nir_lower_doubles_options;
void nir_lower_doubles(nir_shader *shader, nir_lower_doubles_options options);
diff --git a/src/compiler/nir/nir_lower_double_ops.c b/src/compiler/nir/nir_lower_double_ops.c
index e22e822d161..e8ae884d12c 100644
--- a/src/compiler/nir/nir_lower_double_ops.c
+++ b/src/compiler/nir/nir_lower_double_ops.c
@@ -299,6 +299,58 @@ lower_sqrt_rsq(nir_builder *b, nir_ssa_def *src, bool sqrt)
return res;
}
+static nir_ssa_def *
+lower_trunc(nir_builder *b, nir_ssa_def *src)
+{
+ nir_ssa_def *unbiased_exp = nir_isub(b, get_exponent(b, src),
+ nir_imm_int(b, 1023));
+
+ nir_ssa_def *frac_bits = nir_isub(b, nir_imm_int(b, 52), unbiased_exp);
+
+ /*
+ * Decide the operation to apply depending on the unbiased exponent:
+ *
+ * if (unbiased_exp < 0)
+ * return 0
+ * else if (unbiased_exp > 52)
+ * return src
+ * else
+ * return src & (~0 << frac_bits)
+ *
+ * Notice that the else branch is a 64-bit integer operation that we need
+ * to implement in terms of 32-bit integer arithmetics (at least until we
+ * support 64-bit integer arithmetics).
+ */
+
+ /* Compute "~0 << frac_bits" in terms of hi/lo 32-bit integer math */
+ nir_ssa_def *mask_lo =
+ nir_bcsel(b,
+ nir_ige(b, frac_bits, nir_imm_int(b, 32)),
+ nir_imm_int(b, 0),
+ nir_ishl(b, nir_imm_int(b, ~0), frac_bits));
+
+ nir_ssa_def *mask_hi =
+ nir_bcsel(b,
+ nir_ilt(b, frac_bits, nir_imm_int(b, 33)),
+ nir_imm_int(b, ~0),
+ nir_ishl(b,
+ nir_imm_int(b, ~0),
+ nir_isub(b, frac_bits, nir_imm_int(b, 32))));
+
+ nir_ssa_def *src_lo = nir_unpack_double_2x32_split_x(b, src);
+ nir_ssa_def *src_hi = nir_unpack_double_2x32_split_y(b, src);
+
+ return
+ nir_bcsel(b,
+ nir_ilt(b, unbiased_exp, nir_imm_int(b, 0)),
+ nir_imm_double(b, 0.0),
+ nir_bcsel(b, nir_ige(b, unbiased_exp, nir_imm_int(b, 53)),
+ src,
+ nir_pack_double_2x32_split(b,
+ nir_iand(b, mask_lo, src_lo),
+ nir_iand(b, mask_hi, src_hi))));
+}
+
static void
lower_doubles_instr(nir_alu_instr *instr, nir_lower_doubles_options options)
{
@@ -322,6 +374,11 @@ lower_doubles_instr(nir_alu_instr *instr, nir_lower_doubles_options options)
return;
break;
+ case nir_op_ftrunc:
+ if (!(options & nir_lower_dtrunc))
+ return;
+ break;
+
default:
return;
}
@@ -345,6 +402,9 @@ lower_doubles_instr(nir_alu_instr *instr, nir_lower_doubles_options options)
case nir_op_frsq:
result = lower_sqrt_rsq(&bld, src, false);
break;
+ case nir_op_ftrunc:
+ result = lower_trunc(&bld, src);
+ break;
default:
unreachable("unhandled opcode");
}