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nir/range_analysis: Handle vectors better in ssa_def_bits_used

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If a query is made of a vector ssa_def (possibly from an intermediate
result), return all_bits.  If a constant source is a vector, swizzle
the correct component.

Unit tests were added for the constant vector cases.  I don't see a
great way to make unit tests for the other cases.

v2: Add a FINIHSME comment about u16vec2 hardware.

Fixes: 96303a59ea ("nir: Add some range analysis for used bits")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9123>
This commit is contained in:
Ian Romanick
2021-02-17 19:40:07 -08:00
committed by Marge Bot
parent ce649e54f1
commit f2656569c6
3 changed files with 306 additions and 4 deletions
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src/compiler/nir/nir_range_analysis.c
+36 -4
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@@ -1502,6 +1502,18 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
uint64_t bits_used = 0;
uint64_t all_bits = BITFIELD64_MASK(def->bit_size);
/* Querying the bits used from a vector is too hard of a question to
* answer. Return the conservative answer that all bits are used. To
* handle this, the function would need to be extended to be a query of a
* single component of the vector. That would also necessary to fully
* handle the 'num_components > 1' inside the loop below.
*
* FINISHME: This restriction will eventually need to be restricted to be
* useful for hardware that uses u16vec2 as the native 16-bit integer type.
*/
if (def->num_components > 1)
return all_bits;
/* Limit recursion */
if (recur-- <= 0)
return all_bits;
@@ -1512,6 +1524,22 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
nir_alu_instr *use_alu = nir_instr_as_alu(src->parent_instr);
unsigned src_idx = container_of(src, nir_alu_src, src) - use_alu->src;
/* If a user of the value produces a vector result, return the
* conservative answer that all bits are used. It is possible to
* answer this query by looping over the components used. For example,
*
* vec4 32 ssa_5 = load_const(0x0000f000, 0x00000f00, 0x000000f0, 0x0000000f)
* ...
* vec4 32 ssa_8 = iand ssa_7.xxxx, ssa_5
*
* could conceivably return 0x0000ffff when queyring the bits used of
* ssa_7. This is unlikely to be worth the effort because the
* question can eventually answered after the shader has been
* scalarized.
*/
if (use_alu->dest.dest.ssa.num_components > 1)
return all_bits;
switch (use_alu->op) {
case nir_op_u2u8:
case nir_op_i2i8:
@@ -1531,7 +1559,8 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
case nir_op_extract_u8:
case nir_op_extract_i8:
if (src_idx == 0 && nir_src_is_const(use_alu->src[1].src)) {
unsigned chunk = nir_src_as_uint(use_alu->src[1].src);
unsigned chunk = nir_src_comp_as_uint(use_alu->src[1].src,
use_alu->src[1].swizzle[0]);
bits_used |= 0xffull << (chunk * 8);
break;
} else {
@@ -1541,7 +1570,8 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
case nir_op_extract_u16:
case nir_op_extract_i16:
if (src_idx == 0 && nir_src_is_const(use_alu->src[1].src)) {
unsigned chunk = nir_src_as_uint(use_alu->src[1].src);
unsigned chunk = nir_src_comp_as_uint(use_alu->src[1].src,
use_alu->src[1].swizzle[0]);
bits_used |= 0xffffull << (chunk * 16);
break;
} else {
@@ -1561,7 +1591,8 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
case nir_op_iand:
assert(src_idx < 2);
if (nir_src_is_const(use_alu->src[1 - src_idx].src)) {
uint64_t u64 = nir_src_as_uint(use_alu->src[1 - src_idx].src);
uint64_t u64 = nir_src_comp_as_uint(use_alu->src[1 - src_idx].src,
use_alu->src[1 - src_idx].swizzle[0]);
bits_used |= u64;
break;
} else {
@@ -1571,7 +1602,8 @@ ssa_def_bits_used(nir_ssa_def *def, int recur)
case nir_op_ior:
assert(src_idx < 2);
if (nir_src_is_const(use_alu->src[1 - src_idx].src)) {
uint64_t u64 = nir_src_as_uint(use_alu->src[1 - src_idx].src);
uint64_t u64 = nir_src_comp_as_uint(use_alu->src[1 - src_idx].src,
use_alu->src[1 - src_idx].swizzle[0]);
bits_used |= all_bits & ~u64;
break;
} else {