GS/HW: Skip target conversion when alpha doesn't exist

pcsx2/GS/Renderers/HW/GSHwHack.cpp

@@ -1264,7 +1264,7 @@ static bool GetMoveTargetPair(GSRendererHW& r, GSTextureCache::Target** src, GIF
 	const int dst_type =
 		GSLocalMemory::m_psm[dst_desc.PSM].depth ? GSTextureCache::DepthStencil : GSTextureCache::RenderTarget;
 	GSTextureCache::Target* tdst = g_texture_cache->LookupTarget(dst_desc, tsrc->GetUnscaledSize(), tsrc->GetScale(),
-		dst_type, true, 0, false, false, preserve_target, tsrc->GetUnscaledRect());
+		dst_type, true, 0, false, false, preserve_target, preserve_target, tsrc->GetUnscaledRect());
 	if (!tdst)
 	{
 		if (req_target)

pcsx2/GS/Renderers/HW/GSRendererHW.cpp

@@ -1832,11 +1832,14 @@ void GSRendererHW::Draw()
 
 	const bool process_texture = PRIM->TME && !(PRIM->ABE && m_context->ALPHA.IsBlack() && !m_cached_ctx.TEX0.TCC);
 	const u32 frame_end_bp = GSLocalMemory::GetUnwrappedEndBlockAddress(m_cached_ctx.FRAME.Block(), m_cached_ctx.FRAME.FBW, m_cached_ctx.FRAME.PSM, m_r);
-	bool preserve_rt_color =
+	const bool tex_is_rt = (process_texture && m_cached_ctx.TEX0.TBP0 >= m_cached_ctx.FRAME.Block() &&
-		((!no_rt && (!IsDiscardingDstColor() || !PrimitiveCoversWithoutGaps() || !all_depth_tests_pass)) || // Using Dst Color or draw has gaps
+		m_cached_ctx.TEX0.TBP0 < frame_end_bp);
-			(process_texture && m_cached_ctx.TEX0.TBP0 >= m_cached_ctx.FRAME.Block() &&
+	const bool not_writing_to_all = (!PrimitiveCoversWithoutGaps() || !all_depth_tests_pass);
-				m_cached_ctx.TEX0.TBP0 < frame_end_bp)); // Tex is RT
+	const bool preserve_rt_rgb = (!no_rt && (!IsDiscardingDstRGB() || not_writing_to_all));
-	bool preserve_depth = preserve_rt_color || (!no_ds && (!all_depth_tests_pass || !m_cached_ctx.DepthWrite()));
+	const bool preserve_rt_alpha = (!no_rt && (!IsDiscardingDstAlpha() || not_writing_to_all));
+	bool preserve_rt_color = preserve_rt_rgb || preserve_rt_alpha;
+	bool preserve_depth =
+		preserve_rt_color || (!no_ds && (!all_depth_tests_pass || !m_cached_ctx.DepthWrite() || m_cached_ctx.TEST.ATE));
 
 	// SW CLUT Render enable.
 	bool force_preload = GSConfig.PreloadFrameWithGSData;
@@ -2133,6 +2136,7 @@ void GSRendererHW::Draw()
 	const GSVector4i t_size_rect = GSVector4i::loadh(t_size);
 
 	// Ensure draw rect is clamped to framebuffer size. Necessary for updating valid area.
+	const GSVector4i unclamped_draw_rect = m_r;
 	m_r = m_r.rintersect(t_size_rect);
 
 	float target_scale = GetTextureScaleFactor();
@@ -2163,7 +2167,7 @@ void GSRendererHW::Draw()
 		const bool is_square = (t_size.y == t_size.x) && m_r.w >= 1023 && PrimitiveCoversWithoutGaps();
 		const bool is_clear = is_possible_mem_clear && is_square;
 		rt = g_texture_cache->LookupTarget(FRAME_TEX0, t_size, target_scale, GSTextureCache::RenderTarget, true,
-			fm, false, force_preload, preserve_rt_color, m_r);
+			fm, false, force_preload, preserve_rt_rgb, preserve_rt_alpha, unclamped_draw_rect);
 
 		// Draw skipped because it was a clear and there was no target.
 		if (!rt)
@@ -2197,7 +2201,7 @@ void GSRendererHW::Draw()
 		ZBUF_TEX0.PSM = m_cached_ctx.ZBUF.PSM;
 
 		ds = g_texture_cache->LookupTarget(ZBUF_TEX0, t_size, target_scale, GSTextureCache::DepthStencil,
-			m_cached_ctx.DepthWrite(), 0, false, force_preload, preserve_depth, m_r);
+			m_cached_ctx.DepthWrite(), 0, false, force_preload, preserve_depth, preserve_depth, unclamped_draw_rect);
 		if (!ds)
 		{
 			ds = g_texture_cache->CreateTarget(ZBUF_TEX0, t_size, GetValidSize(src), target_scale, GSTextureCache::DepthStencil,
@@ -5814,7 +5818,25 @@ bool GSRendererHW::IsDiscardingDstColor()
 		(!PRIM->ABE || IsOpaque() || m_context->ALPHA.IsBlack()) && // no blending or writing black
 		!m_cached_ctx.TEST.ATE && // not testing alpha (might discard some pixels)
 		!m_cached_ctx.TEST.DATE && // not reading alpha
-		(m_cached_ctx.FRAME.FBMSK & GSLocalMemory::m_psm[m_cached_ctx.FRAME.PSM].fmsk) == 0); // no channels masked
+			(m_cached_ctx.FRAME.FBMSK & GSLocalMemory::m_psm[m_cached_ctx.FRAME.PSM].fmsk) == 0); // no channels masked
+}
+
+bool GSRendererHW::IsDiscardingDstRGB()
+{
+	return ((!PRIM->ABE || IsOpaque() || m_context->ALPHA.IsBlack()) && // no blending or writing black
+			!m_cached_ctx.TEST.ATE && // not testing alpha (might discard some pixels)
+			!m_cached_ctx.TEST.DATE && // not reading alpha
+			((m_cached_ctx.FRAME.FBMSK & GSLocalMemory::m_psm[m_cached_ctx.FRAME.PSM].fmsk) & 0xFFFFFFu) ==
+				0); // RGB isn't masked
+}
+
+bool GSRendererHW::IsDiscardingDstAlpha()
+{
+	return ((!PRIM->ABE || m_context->ALPHA.C != 1) && // not using Ad
+			!m_cached_ctx.TEST.ATE && // not testing alpha (might discard some pixels)
+			!m_cached_ctx.TEST.DATE && // not reading alpha
+			((m_cached_ctx.FRAME.FBMSK & GSLocalMemory::m_psm[m_cached_ctx.FRAME.PSM].fmsk) & 0xFF000000u) ==
+				0); // alpha isn't masked
 }
 
 bool GSRendererHW::PrimitiveCoversWithoutGaps()

pcsx2/GS/Renderers/HW/GSRendererHW.h

@@ -62,6 +62,8 @@ private:
 	u32 GetConstantDirectWriteMemClearColor() const;
 	bool IsReallyDithered() const;
 	bool IsDiscardingDstColor();
+	bool IsDiscardingDstRGB();
+	bool IsDiscardingDstAlpha();
 	bool PrimitiveCoversWithoutGaps();
 
 	enum class CLUTDrawTestResult

pcsx2/GS/Renderers/HW/GSTextureCache.cpp

@@ -1241,7 +1241,7 @@ GSVector2i GSTextureCache::ScaleRenderTargetSize(const GSVector2i& sz, float sca
 }
 
 GSTextureCache::Target* GSTextureCache::LookupTarget(GIFRegTEX0 TEX0, const GSVector2i& size, float scale, int type,
-	bool used, u32 fbmask, bool is_frame, bool preload, bool preserve_target, const GSVector4i draw_rect)
+	bool used, u32 fbmask, bool is_frame, bool preload, bool preserve_rgb, bool preserve_alpha, const GSVector4i draw_rect)
 {
 	const GSLocalMemory::psm_t& psm_s = GSLocalMemory::m_psm[TEX0.PSM];
 	const u32 bp = TEX0.TBP0;
@@ -1393,6 +1393,7 @@ GSTextureCache::Target* GSTextureCache::LookupTarget(GIFRegTEX0 TEX0, const GSVe
 		}
 
 		// If our RGB was invalidated, we need to pull it from depth.
+		const bool preserve_target = preserve_rgb || preserve_alpha;
 		if (type == RenderTarget && (preserve_target || !dst->m_valid.rintersect(draw_rect).eq(dst->m_valid)) &&
 			!dst->m_valid_rgb && !FullRectDirty(dst, 0x7) &&
 			(GSLocalMemory::m_psm[TEX0.PSM].trbpp < 24 || fbmask != 0x00FFFFFFu))
@@ -1479,6 +1480,15 @@ GSTextureCache::Target* GSTextureCache::LookupTarget(GIFRegTEX0 TEX0, const GSVe
 		if (dst_match)
 		{
 			calcRescale(dst_match);
+
+			// If we don't need A, and the existing target doesn't have valid alpha, don't bother converting it.
+			const bool has_alpha = dst_match->m_valid_alpha_low || dst_match->m_valid_alpha_high;
+			const bool preserve_target = (preserve_rgb || (preserve_alpha && has_alpha)) ||
+										 !draw_rect.rintersect(dst_match->m_valid).eq(dst_match->m_valid);
+
+			// Clear instead of invalidating if there is anything which isn't touched.
+			clear |= (!preserve_target && fbmask != 0);
+
 			dst = Target::Create(TEX0, new_size.x, new_size.y, scale, type, clear);
 			if (!dst)
 				return nullptr;
@@ -1509,7 +1519,8 @@ GSTextureCache::Target* GSTextureCache::LookupTarget(GIFRegTEX0 TEX0, const GSVe
 				shader = (fmt_16_bits) ? ShaderConvert::FLOAT16_TO_RGB5A1 : ShaderConvert::FLOAT32_TO_RGBA8;
 			}
 
-			if (!preserve_target && draw_rect.rintersect(dst_match->m_valid).eq(dst_match->m_valid))
+
+			if (!preserve_target)
 			{
 				GL_INS("TC: Not converting existing %s[%x] because it's fully overwritten.", to_string(!type), dst->m_TEX0.TBP0);
 			}

pcsx2/GS/Renderers/HW/GSTextureCache.h

@@ -478,7 +478,7 @@ public:
 
 	Target* FindTargetOverlap(Target* target, int type, int psm);
 	Target* LookupTarget(GIFRegTEX0 TEX0, const GSVector2i& size, float scale, int type, bool used = true, u32 fbmask = 0,
-		bool is_frame = false, bool preload = GSConfig.PreloadFrameWithGSData, bool preserve_target = true,
+		bool is_frame = false, bool preload = GSConfig.PreloadFrameWithGSData, bool preserve_rgb = true, bool preserve_alpha = true,
 		const GSVector4i draw_rc = GSVector4i::zero());
 	Target* CreateTarget(GIFRegTEX0 TEX0, const GSVector2i& size, const GSVector2i& valid_size,float scale, int type, bool used = true, u32 fbmask = 0,
 		bool is_frame = false, bool preload = GSConfig.PreloadFrameWithGSData, bool preserve_target = true,