From 71aaad23fba5e4ab4e9610b99384078d1c0d6d96 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Sun, 10 Dec 2023 12:21:07 +0100
Subject: [PATCH] Fix issue with zero-vertex draw calls. Though, should maybe
 just filter them out earlier.

---
 GPU/Common/DrawEngineCommon.cpp    | 17 ++++++++---------
 GPU/Common/VertexDecoderCommon.cpp |  6 +++++-
 GPU/Vulkan/DrawEngineVulkan.cpp    |  8 ++++++++
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/GPU/Common/DrawEngineCommon.cpp b/GPU/Common/DrawEngineCommon.cpp
index eec4070f51d3..190f6160d4cd 100644
--- a/GPU/Common/DrawEngineCommon.cpp
+++ b/GPU/Common/DrawEngineCommon.cpp
@@ -899,8 +899,11 @@ bool DrawEngineCommon::SubmitPrim(const void *verts, const void *inds, GEPrimiti
 	*bytesRead = vertexCount * dec_->VertexSize();
 
 	// Check that we have enough vertices to form the requested primitive.
-	if (vertexCount < 3 && ((vertexCount < 2 && prim > 0) || (prim > GE_PRIM_LINE_STRIP && prim != GE_PRIM_RECTANGLES)))
-		return false;
+	if (vertexCount < 3) {
+		if ((vertexCount < 2 && prim > 0) || (prim > GE_PRIM_LINE_STRIP && prim != GE_PRIM_RECTANGLES)) {
+			return false;
+		}
+	}
 
 	bool applySkin = (vertTypeID & GE_VTYPE_WEIGHT_MASK) && decOptions_.applySkinInDecode;
 
@@ -919,10 +922,10 @@ bool DrawEngineCommon::SubmitPrim(const void *verts, const void *inds, GEPrimiti
 	if (inds && numDrawVerts_ > decodeVertsCounter_ && drawVerts_[numDrawVerts_ - 1].verts == verts && !applySkin) {
 		// Same vertex pointer as a previous un-decoded draw call - let's just extend the decode!
 		di.vertDecodeIndex = numDrawVerts_ - 1;
-		DeferredVerts &dv = drawVerts_[numDrawVerts_ - 1];
 		u16 lb;
 		u16 ub;
 		GetIndexBounds(inds, vertexCount, vertTypeID, &lb, &ub);
+		DeferredVerts &dv = drawVerts_[numDrawVerts_ - 1];
 		if (lb < dv.indexLowerBound)
 			dv.indexLowerBound = lb;
 		if (ub > dv.indexUpperBound)
@@ -933,12 +936,8 @@ bool DrawEngineCommon::SubmitPrim(const void *verts, const void *inds, GEPrimiti
 		dv.verts = verts;
 		dv.vertexCount = vertexCount;
 		dv.uvScale = gstate_c.uv;
-		if (inds) {
-			GetIndexBounds(inds, vertexCount, vertTypeID, &dv.indexLowerBound, &dv.indexUpperBound);
-		} else {
-			dv.indexLowerBound = 0;
-			dv.indexUpperBound = vertexCount - 1;
-		}
+		// Does handle the unindexed case.
+		GetIndexBounds(inds, vertexCount, vertTypeID, &dv.indexLowerBound, &dv.indexUpperBound);
 	}
 
 	vertexCountInDrawCalls_ += vertexCount;
diff --git a/GPU/Common/VertexDecoderCommon.cpp b/GPU/Common/VertexDecoderCommon.cpp
index cc8b6452e2b1..e500c69db5fa 100644
--- a/GPU/Common/VertexDecoderCommon.cpp
+++ b/GPU/Common/VertexDecoderCommon.cpp
@@ -154,7 +154,11 @@ void GetIndexBounds(const void *inds, int count, u32 vertType, u16 *indexLowerBo
 		*indexUpperBound = (u16)upperBound;
 	} else {
 		*indexLowerBound = 0;
-		*indexUpperBound = count - 1;
+		if (count > 0) {
+			*indexUpperBound = count - 1;
+		} else {
+			*indexUpperBound = 0;
+		}
 	}
 }
 
diff --git a/GPU/Vulkan/DrawEngineVulkan.cpp b/GPU/Vulkan/DrawEngineVulkan.cpp
index 5149a37c41e3..670338bbb4d2 100644
--- a/GPU/Vulkan/DrawEngineVulkan.cpp
+++ b/GPU/Vulkan/DrawEngineVulkan.cpp
@@ -376,8 +376,11 @@ void DrawEngineVulkan::DoFlush() {
 			lastVType_ |= (1 << 26);
 			dec_ = GetVertexDecoder(lastVType_);
 		}
+		int prevDecodedVerts = numDecodedVerts_;
+
 		DecodeVerts(decoded_);
 		DecodeInds();
+
 		bool hasColor = (lastVType_ & GE_VTYPE_COL_MASK) != GE_VTYPE_COL_NONE;
 		if (gstate.isModeThrough()) {
 			gstate_c.vertexFullAlpha = gstate_c.vertexFullAlpha && (hasColor || gstate.getMaterialAmbientA() == 255);
@@ -385,6 +388,11 @@ void DrawEngineVulkan::DoFlush() {
 			gstate_c.vertexFullAlpha = gstate_c.vertexFullAlpha && ((hasColor && (gstate.materialupdate & 1)) || gstate.getMaterialAmbientA() == 255) && (!gstate.isLightingEnabled() || gstate.getAmbientA() == 255);
 		}
 
+		int vcount = indexGen.VertexCount();
+		if (numDecodedVerts_ > 10 * vcount) {
+			decIndex_ = decIndex_;
+		}
+
 		gpuStats.numUncachedVertsDrawn += indexGen.VertexCount();
 		prim = indexGen.Prim();
 		// Undo the strip optimization, not supported by the SW code yet.