[Mesa-dev] [PATCH 4/4] swr: [rasterizer core] use ClearTile helper to store fast clears

[Ilia Mirkin]

No point in clearing the hot tile and then storing that - may as well
just store the clear color to the surface directly. Use the helper that
already exists for this purpose.

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---

My theory is that this is going to be a very modest perf improvement. Instead
of first clearing the hot tile and then storing it, we store the clear color
directly.

It does bring up a rare case where a tile might be cleared, stored, and then
re-used with the same buffer. In that case, the former logic would avoid the
load while the new logic will end up reloading the clear color/etc. There was
a grand total of one piglit that was hit by this:

  fbo-attachments-blit-scaled-linear

(and that is the reason that we have to set the hottile to INVALID rather than
the post state when storing.)

 src/gallium/drivers/swr/rasterizer/core/backend.cpp | 17 ++++++++++-------
 src/gallium/drivers/swr/rasterizer/core/tilemgr.cpp | 15 +++++----------
 2 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/gallium/drivers/swr/rasterizer/core/backend.cpp b/src/gallium/drivers/swr/rasterizer/core/backend.cpp
index c45c0a7..ff08233 100644
--- a/src/gallium/drivers/swr/rasterizer/core/backend.cpp
+++ b/src/gallium/drivers/swr/rasterizer/core/backend.cpp
@@ -358,16 +358,19 @@ void ProcessStoreTileBE(DRAW_CONTEXT *pDC, uint32_t workerId, uint32_t macroTile
     HOTTILE *pHotTile = pContext->pHotTileMgr->GetHotTileNoLoad(pContext, pDC, macroTile, attachment, false);
     if (pHotTile)
     {
-        // clear if clear is pending (i.e., not rendered to), then mark as dirty for store.
+        // clear the surface directly
         if (pHotTile->state == HOTTILE_CLEAR)
         {
-            PFN_CLEAR_TILES pfnClearTiles = sClearTilesTable[srcFormat];
-            SWR_ASSERT(pfnClearTiles != nullptr);
-
-            pfnClearTiles(pDC, attachment, macroTile, pHotTile->renderTargetArrayIndex, pHotTile->clearData, pDesc->rect);
+            pContext->pfnClearTile(GetPrivateState(pDC), attachment,
+                x * KNOB_MACROTILE_X_DIM, y * KNOB_MACROTILE_Y_DIM,
+                pHotTile->renderTargetArrayIndex,
+                (const float *)pHotTile->clearData);
+
+            // Since the state is effectively uninitialized, make sure that we
+            // reload any data.
+            pHotTile->state = HOTTILE_INVALID;
         }
-
-        if (pHotTile->state == HOTTILE_DIRTY || pDesc->postStoreTileState == (SWR_TILE_STATE)HOTTILE_DIRTY)
+        else if (pHotTile->state == HOTTILE_DIRTY || pDesc->postStoreTileState == (SWR_TILE_STATE)HOTTILE_DIRTY)
         {
             int32_t destX = KNOB_MACROTILE_X_DIM * x;
             int32_t destY = KNOB_MACROTILE_Y_DIM * y;
diff --git a/src/gallium/drivers/swr/rasterizer/core/tilemgr.cpp b/src/gallium/drivers/swr/rasterizer/core/tilemgr.cpp
index f398667..a4a6152 100644
--- a/src/gallium/drivers/swr/rasterizer/core/tilemgr.cpp
+++ b/src/gallium/drivers/swr/rasterizer/core/tilemgr.cpp
@@ -151,17 +151,12 @@ HOTTILE* HotTileMgr::GetHotTile(SWR_CONTEXT* pContext, DRAW_CONTEXT* pDC, uint32
 
             if (hotTile.state == HOTTILE_CLEAR)
             {
-                if (attachment == SWR_ATTACHMENT_STENCIL)
-                    ClearStencilHotTile(&hotTile);
-                else if (attachment == SWR_ATTACHMENT_DEPTH)
-                    ClearDepthHotTile(&hotTile);
-                else
-                    ClearColorHotTile(&hotTile);
-
-                hotTile.state = HOTTILE_DIRTY;
+                pContext->pfnClearTile(GetPrivateState(pDC), attachment,
+                    x * KNOB_MACROTILE_X_DIM, y * KNOB_MACROTILE_Y_DIM,
+                    hotTile.renderTargetArrayIndex,
+                    (const float *)hotTile.clearData);
             }
-
-            if (hotTile.state == HOTTILE_DIRTY)
+            else if (hotTile.state == HOTTILE_DIRTY)
             {
                 pContext->pfnStoreTile(GetPrivateState(pDC), format, attachment,
                     x * KNOB_MACROTILE_X_DIM, y * KNOB_MACROTILE_Y_DIM, hotTile.renderTargetArrayIndex, hotTile.pBuffer);
-- 
2.7.3