i965,iris: Move guardband calculations to a common location

Reviewed-by: Kenneth Graunke <[email protected]>
Reviewed-by: Lionel Landwerlin <[email protected]>

2 files changed, 118 insertions, 0 deletions

diff --git a/src/intel/common/gen_guardband.h b/src/intel/common/gen_guardband.h
new file mode 100644
index 00000000000..757324fd2ee
--- /dev/null
+++ b/src/intel/common/gen_guardband.h
@@ -0,0 +1,117 @@
+/*
+ * Copyright © 2019 Intel 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 GEN_GUARDBAND_H
+#define GEN_GUARDBAND_H
+
+static inline void
+gen_calculate_guardband_size(uint32_t fb_width, uint32_t fb_height,
+                             float m00, float m11, float m30, float m31,
+                             float *xmin, float *xmax,
+                             float *ymin, float *ymax)
+{
+   /* According to the "Vertex X,Y Clamping and Quantization" section of the
+    * Strips and Fans documentation:
+    *
+    * "The vertex X and Y screen-space coordinates are also /clamped/ to the
+    *  fixed-point "guardband" range supported by the rasterization hardware"
+    *
+    * and
+    *
+    * "In almost all circumstances, if an object’s vertices are actually
+    *  modified by this clamping (i.e., had X or Y coordinates outside of
+    *  the guardband extent the rendered object will not match the intended
+    *  result.  Therefore software should take steps to ensure that this does
+    *  not happen - e.g., by clipping objects such that they do not exceed
+    *  these limits after the Drawing Rectangle is applied."
+    *
+    * I believe the fundamental restriction is that the rasterizer (in
+    * the SF/WM stages) have a limit on the number of pixels that can be
+    * rasterized.  We need to ensure any coordinates beyond the rasterizer
+    * limit are handled by the clipper.  So effectively that limit becomes
+    * the clipper's guardband size.
+    *
+    * It goes on to say:
+    *
+    * "In addition, in order to be correctly rendered, objects must have a
+    *  screenspace bounding box not exceeding 8K in the X or Y direction.
+    *  This additional restriction must also be comprehended by software,
+    *  i.e., enforced by use of clipping."
+    *
+    * This makes no sense.  Gen7+ hardware supports 16K render targets,
+    * and you definitely need to be able to draw polygons that fill the
+    * surface.  Our assumption is that the rasterizer was limited to 8K
+    * on Sandybridge, which only supports 8K surfaces, and it was actually
+    * increased to 16K on Ivybridge and later.
+    *
+    * So, limit the guardband to 16K on Gen7+ and 8K on Sandybridge.
+    */
+   const float gb_size = GEN_GEN >= 7 ? 16384.0f : 8192.0f;
+
+   /* Workaround: prevent gpu hangs on SandyBridge
+    * by disabling guardband clipping for odd dimensions.
+    */
+   if (GEN_GEN == 6 && (fb_width & 1 || fb_height & 1)) {
+      *xmin = -1.0f;
+      *xmax =  1.0f;
+      *ymin = -1.0f;
+      *ymax =  1.0f;
+      return;
+   }
+
+   if (m00 != 0 && m11 != 0) {
+      /* First, we compute the screen-space render area */
+      const float ss_ra_xmin = MIN3(        0, m30 + m00, m30 - m00);
+      const float ss_ra_xmax = MAX3( fb_width, m30 + m00, m30 - m00);
+      const float ss_ra_ymin = MIN3(        0, m31 + m11, m31 - m11);
+      const float ss_ra_ymax = MAX3(fb_height, m31 + m11, m31 - m11);
+
+      /* We want the guardband to be centered on that */
+      const float ss_gb_xmin = (ss_ra_xmin + ss_ra_xmax) / 2 - gb_size;
+      const float ss_gb_xmax = (ss_ra_xmin + ss_ra_xmax) / 2 + gb_size;
+      const float ss_gb_ymin = (ss_ra_ymin + ss_ra_ymax) / 2 - gb_size;
+      const float ss_gb_ymax = (ss_ra_ymin + ss_ra_ymax) / 2 + gb_size;
+
+      /* Now we need it in native device coordinates */
+      const float ndc_gb_xmin = (ss_gb_xmin - m30) / m00;
+      const float ndc_gb_xmax = (ss_gb_xmax - m30) / m00;
+      const float ndc_gb_ymin = (ss_gb_ymin - m31) / m11;
+      const float ndc_gb_ymax = (ss_gb_ymax - m31) / m11;
+
+      /* Thanks to Y-flipping and ORIGIN_UPPER_LEFT, the Y coordinates may be
+       * flipped upside-down.  X should be fine though.
+       */
+      assert(ndc_gb_xmin <= ndc_gb_xmax);
+      *xmin = ndc_gb_xmin;
+      *xmax = ndc_gb_xmax;
+      *ymin = MIN2(ndc_gb_ymin, ndc_gb_ymax);
+      *ymax = MAX2(ndc_gb_ymin, ndc_gb_ymax);
+   } else {
+      /* The viewport scales to 0, so nothing will be rendered. */
+      *xmin = 0.0f;
+      *xmax = 0.0f;
+      *ymin = 0.0f;
+      *ymax = 0.0f;
+   }
+}
+
+#endif /* GEN_GUARDBAND_H */
diff --git a/src/intel/common/meson.build b/src/intel/common/meson.build
index bf8d6feab2a..540d78f90b5 100644
--- a/src/intel/common/meson.build
+++ b/src/intel/common/meson.build
@@ -28,6 +28,7 @@ files_libintel_common = files(
   'gen_disasm.c',
   'gen_disasm.h',
   'gen_gem.h',
+  'gen_guardband.h',
   'gen_l3_config.c',
   'gen_l3_config.h',
   'gen_urb_config.c',