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nir/algebraic: Remove spurious conversions from inside logic ops

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Not only does this eliminate a bunch of unnecessary type converting
MOVs, but it can also enable some SWAR.  The
dEQP-VK.spirv_assembly.type.vec3.i8.bitwise_xor_frag test does
something about like:

    c = a.x ^ b.x;
    d = a.y ^ b.y;
    e = a.z ^ b.z;

After this change, it looks more like:

    uint t = i8vec3AsUint(a) ^ i8vec3AsUint(b);
    c = extract_u8(t, 0);
    d = extract_u8(t, 1);
    e = extract_u8(t, 2);

On Ice Lake, this results in:

SIMD8 shader: 41 instructions. 1 loops. 3804 cycles. 0:0 spills:fills, 5 sends
SIMD8 shader: 31 instructions. 1 loops. 2844 cycles. 0:0 spills:fills, 5 sends

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9025>
This commit is contained in:
Ian Romanick 2021-01-25 16:31:44 -08:00 • committed by Marge Bot
parent 7c83aa0518
commit 89f639c0ca
1 changed files with 27 additions and 0 deletions
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27
src/compiler/nir/nir_opt_algebraic.py
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@ -829,6 +829,33 @@ optimizations.extend([
(('i2f16', ('i2imp', 'a@32')), ('i2f16', a)),
])
# Clean up junk left from 8-bit integer to 16-bit integer lowering.
optimizations.extend([
# The u2u16(u2u8(X)) just masks off the upper 8-bits of X. This can be
# accomplished by mask the upper 8-bit of the immediate operand to the
# iand instruction. Often times, both patterns will end up being applied
# to the same original expression tree.
(('iand', ('u2u16', ('u2u8', 'a@16')), '#b'), ('iand', a, ('iand', b, 0xff))),
(('u2u16', ('u2u8(is_used_once)', ('iand', 'a@16', '#b'))), ('iand', a, ('iand', b, 0xff))),
])
for op in ['iand', 'ior', 'ixor']:
optimizations.extend([
(('u2u8', (op, ('u2u16', ('u2u8', 'a@16')), ('u2u16', ('u2u8', 'b@16')))), ('u2u8', (op, a, b))),
(('u2u8', (op, ('u2u16', ('u2u8', 'a@32')), ('u2u16', ('u2u8', 'b@32')))), ('u2u8', (op, a, b))),
# Undistribute extract from a logic op
((op, ('extract_i8', a, '#b'), ('extract_i8', c, b)), ('extract_i8', (op, a, c), b)),
((op, ('extract_u8', a, '#b'), ('extract_u8', c, b)), ('extract_u8', (op, a, c), b)),
((op, ('extract_i16', a, '#b'), ('extract_i16', c, b)), ('extract_i16', (op, a, c), b)),
((op, ('extract_u16', a, '#b'), ('extract_u16', c, b)), ('extract_u16', (op, a, c), b)),
# Undistribute shifts from a logic op
((op, ('ushr(is_used_once)', a, '#b'), ('ushr', c, b)), ('ushr', (op, a, c), b)),
((op, ('ishr(is_used_once)', a, '#b'), ('ishr', c, b)), ('ishr', (op, a, c), b)),
((op, ('ishl(is_used_once)', a, '#b'), ('ishl', c, b)), ('ishl', (op, a, c), b)),
])
# Integer sizes
for s in [8, 16, 32, 64]:
optimizations.extend([