From: Ian Romanick <ian.d.roman...@intel.com>
Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
---
src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 22 +++++++++++++++++++++-
src/mesa/drivers/dri/i965/brw_vec4_nir.cpp | 21 ++++++++++++++++++++-
2 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index f8db28a..562b06d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -1385,7 +1385,27 @@ fs_visitor::nir_emit_alu(const fs_builder &bld,
nir_alu_instr *instr)
case nir_op_find_lsb:
assert(nir_dest_bit_size(instr->dest.dest) < 64);
- bld.FBL(result, op[0]);
+
+ if (devinfo->gen < 7) {
+ fs_reg temp = vgrf(glsl_type::int_type);
+
+ /* (x & -x) generates a value that consists of only the LSB of x.
+ * For all powers of 2, findMSB(y) == findLSB(y).
+ */
+ fs_reg src = retype(op[0], BRW_REGISTER_TYPE_D);
+ fs_reg negated_src = src;
+
+ /* One must be negated, and the other must be non-negated. It
+ * doesn't matter which is which.
+ */
+ negated_src.negate = true;
+ src.negate = false;
+
+ bld.AND(temp, src, negated_src);
+ nir_emit_find_msb_using_lzd(bld, result, temp, false);
+ } else {
+ bld.FBL(result, op[0]);
+ }
break;
case nir_op_ubitfield_extract:
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
index 2fc2cf2..a25ccba 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
@@ -1530,7 +1530,26 @@ vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
}
case nir_op_find_lsb:
- emit(FBL(dst, op[0]));
+ if (devinfo->gen < 7) {
+ src_reg temp = src_reg(this, glsl_type::ivec4_type);
+
+ /* (x & -x) generates a value that consists of only the LSB of x.
+ * For all powers of 2, findMSB(y) == findLSB(y).
+ */
+ src_reg src = src_reg(retype(op[0], BRW_REGISTER_TYPE_D));
+ src_reg negated_src = src;
+
+ /* One must be negated, and the other must be non-negated. It
+ * doesn't matter which is which.
+ */
+ negated_src.negate = true;
+ src.negate = false;
+
+ emit(AND(dst_reg(temp), src, negated_src));
+ nir_emit_find_msb_using_lzd(dst, temp, false);
+ } else {
+ emit(FBL(dst, op[0]));
+ }
break;
case nir_op_ubitfield_extract:
--
2.5.5
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/mesa-dev
