[Mesa-dev] [PATCH 18.0] swr/rast: Fix index buffer overfetch issue for non-indexed draws

[George Kyriazis]

Populate pLastIndex, even for the non-indexed case.  An zero pLastIndex
can cause the index offsets inside the fetcher to have non-sensical values
that can be either very large positive or very large negative numbers.

Cherry-pick of 539de78633 for 18.0.  Surrounding context is different for
18.0 branch, hence the need for a separate patch.

cc: "18.0" <mesa-stable at lists.freedesktop.org>
---
 src/gallium/drivers/swr/rasterizer/core/frontend.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/gallium/drivers/swr/rasterizer/core/frontend.cpp b/src/gallium/drivers/swr/rasterizer/core/frontend.cpp
index 9600f78..ce6cb68 100644
--- a/src/gallium/drivers/swr/rasterizer/core/frontend.cpp
+++ b/src/gallium/drivers/swr/rasterizer/core/frontend.cpp
@@ -1724,6 +1724,21 @@ void ProcessDraw(
 
             if (i < endVertex)
             {
+                if (!IsIndexedT::value)
+                {
+                    fetchInfo_lo.pLastIndex = fetchInfo_lo.pIndices;
+                    uint32_t offset;
+                    offset = std::min(endVertex-i, (uint32_t) KNOB_SIMD16_WIDTH);
+#if USE_SIMD16_SHADERS
+                    fetchInfo_lo.pLastIndex += offset;
+#else
+                    fetchInfo_lo.pLastIndex += std::min(offset, (uint32_t) KNOB_SIMD_WIDTH);
+                    uint32_t offset2 = std::min(offset, (uint32_t) KNOB_SIMD16_WIDTH)-KNOB_SIMD_WIDTH;
+                    assert(offset >= 0);
+                    fetchInfo_hi.pLastIndex = fetchInfo_hi.pIndices;
+                    fetchInfo_hi.pLastIndex += offset2;
+#endif
+                }
                 // 1. Execute FS/VS for a single SIMD.
                 AR_BEGIN(FEFetchShader, pDC->drawId);
 #if USE_SIMD16_SHADERS
-- 
2.7.4