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panfrost: Factor out panfrost_compute_magic_divisor

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The algorithm doesn't need to be tangled up in details about the
attribute records themselves. We'll need to compute magic divisors for
gl_InstanceID in a second.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
This commit is contained in:
Alyssa Rosenzweig 2019-12-24 21:35:52 -05:00
parent 31305e1b28
commit 467ae0d39d
1 changed files with 41 additions and 30 deletions
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71
src/panfrost/encoder/pan_attributes.c
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@ -156,6 +156,44 @@ panfrost_padded_vertex_count(unsigned vertex_count)
/* The much, much more irritating case -- instancing is enabled. See
* panfrost_job.h for notes on how this works */
static unsigned
panfrost_compute_magic_divisor(unsigned hw_divisor, unsigned *o_shift, unsigned *extra_flags)
{
/* We have a NPOT divisor. Here's the fun one (multipling by
* the inverse and shifting) */
/* floor(log2(d)) */
unsigned shift = util_logbase2(hw_divisor);
/* m = ceil(2^(32 + shift) / d) */
uint64_t shift_hi = 32 + shift;
uint64_t t = 1ll << shift_hi;
double t_f = t;
double hw_divisor_d = hw_divisor;
double m_f = ceil(t_f / hw_divisor_d);
unsigned m = m_f;
/* Default case */
uint32_t magic_divisor = m;
/* e = 2^(shift + 32) % d */
uint64_t e = t % hw_divisor;
/* Apply round-down algorithm? e <= 2^shift?. XXX: The blob
* seems to use a different condition */
if (e <= (1ll << shift)) {
magic_divisor = m - 1;
*extra_flags = 1;
}
/* Top flag implicitly set */
assert(magic_divisor & (1u << 31));
magic_divisor &= ~(1u << 31);
*o_shift = shift;
return magic_divisor;
}
unsigned
panfrost_vertex_instanced(
unsigned padded_count,
@ -188,36 +226,10 @@ panfrost_vertex_instanced(
return 1;
} else {
/* We have a NPOT divisor. Here's the fun one (multipling by
* the inverse and shifting) */
unsigned shift = 0, extra_flags = 0;
/* floor(log2(d)) */
unsigned shift = util_logbase2(hw_divisor);
/* m = ceil(2^(32 + shift) / d) */
uint64_t shift_hi = 32 + shift;
uint64_t t = 1ll << shift_hi;
double t_f = t;
double hw_divisor_d = hw_divisor;
double m_f = ceil(t_f / hw_divisor_d);
unsigned m = m_f;
/* Default case */
uint32_t magic_divisor = m, extra_flags = 0;
/* e = 2^(shift + 32) % d */
uint64_t e = t % hw_divisor;
/* Apply round-down algorithm? e <= 2^shift?. XXX: The blob
* seems to use a different condition */
if (e <= (1ll << shift)) {
magic_divisor = m - 1;
extra_flags = 1;
}
/* Top flag implicitly set */
assert(magic_divisor & (1u << 31));
magic_divisor &= ~(1u << 31);
attrs[1].magic_divisor =
panfrost_compute_magic_divisor(hw_divisor, &shift, &extra_flags);
/* Upload to two different slots */
@ -226,7 +238,6 @@ panfrost_vertex_instanced(
attrs[0].extra_flags = extra_flags;
attrs[1].unk = 0x20;
attrs[1].magic_divisor = magic_divisor;
attrs[1].zero = 0;
attrs[1].divisor = divisor;