/*
* Copyright © 2020 Valve Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef __FREEDRENO_GUARDBAND_H__
#define __FREEDRENO_GUARDBAND_H__
#include
#include
#include
static inline unsigned
fd_calc_guardband(float offset, float scale, bool is_a3xx)
{
/* On a3xx, the viewport max is 4k and the docs say the max guardband
* width is 8k. That is, GRAS cannot handle triangle coordinates more than
* 8k, positive or negative. On a4xx+ the viewport width was bumped to
* 16k, and so the guardband width was necessarily also bumped. Note that
* the numbers here should correspond to
* VkPhysicalDeviceLimits::viewportBoundsRange in Vulkan.
*/
const float gb_min = is_a3xx ? -8192. : -32768.;
const float gb_max = is_a3xx ? 8191. : 32767.;
/* Clipping happens in normalized device coordinates, so we have to
* transform gb_min and gb_max to ndc using the inverse of the viewport
* transform. Avoid flipping min and max by using the absolute value of
* the scale.
*/
const float gb_min_ndc = (gb_min - offset) / fabsf(scale);
const float gb_max_ndc = (gb_max - offset) / fabsf(scale);
/* There's only one GB_ADJ field, so presumably the guardband is
* [-GB_ADJ, GB_ADJ] like on Radeon. It's always safe to make the
* guardband smaller, so we have to take the min to get the largest range
* contained in [gb_min_ndc, gb_max_ndc].
*/
const float gb_adj = fminf(-gb_min_ndc, gb_max_ndc);
/* The viewport should always be contained in the guardband. */
assert(gb_adj >= 1.0);
/* frexp returns an unspecified value if given an infinite value, which
* can happen if scale == 0.
*/
if (isinf(gb_adj))
return 0x1ff;
/* Convert gb_adj to 3.6 floating point, rounding down since it's always
* safe to make the guard band smaller (but not the other way around!).
*
* Note: After converting back to a float, the value the blob returns here
* is sometimes a little smaller than the value we return. This seems to
* happen around the boundary between two different rounded values. For
* example, using the a6xx blob:
*
* min | width | unrounded gb_adj | blob result | mesa result
* ------------------------------------------------------------
* 0 | 510 | 127.498 | 127. | 127.
* 0 | 511 | 127.247 | 126. | 127.
* 0 | 512 | 126.996 | 126. | 126.
*
* The guardband must be 32767 wide, since that's what the blob reports
* for viewportBoundsRange, so I'm guessing that they're rounding slightly
* more conservatively somehow.
*/
int gb_adj_exp;
float gb_adj_mantissa = frexpf(gb_adj, &gb_adj_exp);
assert(gb_adj_exp > 0);
/* Round non-representable numbers down to the largest possible number. */
if (gb_adj_exp > 8)
return 0x1ff;
return ((gb_adj_exp - 1) << 6) |
((unsigned) truncf(gb_adj_mantissa * (1 << 7)) - (1 << 6));
}
#endif /* __FREEDRENO_GUARDBAND_H__ */