| /* |
| * 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 <math.h> |
| #include <stdbool.h> |
| #include <assert.h> |
| |
| 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__ */ |