From ae22644d4347b34f08a5b157288f72587b147676 Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Sat, 13 Mar 2021 03:30:10 +0000
Subject: [PATCH] CelOutputBuffer: Recover lost performance

Makes `RenderLine` hotspot manipulate the buffer directly again.

FPS: 195 -> 275
---
 Source/render.cpp | 120 ++++++++++++++++++++++++----------------------
 defs.h            |  12 +++++
 2 files changed, 76 insertions(+), 56 deletions(-)

diff --git a/Source/render.cpp b/Source/render.cpp
index 4f2460263..28314448c 100644
--- a/Source/render.cpp
+++ b/Source/render.cpp
@@ -9,6 +9,8 @@ DEVILUTION_BEGIN_NAMESPACE
 
 #define NO_OVERDRAW
 
+namespace {
+
 enum {
 	RT_SQUARE,
 	RT_TRANSPARENT,
@@ -19,7 +21,7 @@ enum {
 };
 
 /** Fully transparent variant of WallMask. */
-static DWORD WallMask_FullyTrasparent[TILE_HEIGHT] = {
+const DWORD WallMask_FullyTrasparent[TILE_HEIGHT] = {
 	0x00000000,
 	0x00000000,
 	0x00000000,
@@ -54,7 +56,7 @@ static DWORD WallMask_FullyTrasparent[TILE_HEIGHT] = {
 	0x00000000
 };
 /** Transparent variant of RightMask. */
-static DWORD RightMask_Transparent[TILE_HEIGHT] = {
+const DWORD RightMask_Transparent[TILE_HEIGHT] = {
 	0xC0000000,
 	0xF0000000,
 	0xFC000000,
@@ -89,7 +91,7 @@ static DWORD RightMask_Transparent[TILE_HEIGHT] = {
 	0xFFFFFFFF
 };
 /** Transparent variant of LeftMask. */
-static DWORD LeftMask_Transparent[TILE_HEIGHT] = {
+const DWORD LeftMask_Transparent[TILE_HEIGHT] = {
 	0x00000003,
 	0x0000000F,
 	0x0000003F,
@@ -124,7 +126,7 @@ static DWORD LeftMask_Transparent[TILE_HEIGHT] = {
 	0xFFFFFFFF
 };
 /** Specifies the draw masks used to render transparency of the right side of tiles. */
-static DWORD RightMask[TILE_HEIGHT] = {
+const DWORD RightMask[TILE_HEIGHT] = {
 	0xEAAAAAAA,
 	0xF5555555,
 	0xFEAAAAAA,
@@ -159,7 +161,7 @@ static DWORD RightMask[TILE_HEIGHT] = {
 	0xFFFFFFFF
 };
 /** Specifies the draw masks used to render transparency of the left side of tiles. */
-static DWORD LeftMask[TILE_HEIGHT] = {
+const DWORD LeftMask[TILE_HEIGHT] = {
 	0xAAAAAAAB,
 	0x5555555F,
 	0xAAAAAABF,
@@ -194,7 +196,7 @@ static DWORD LeftMask[TILE_HEIGHT] = {
 	0xFFFFFFFF
 };
 /** Specifies the draw masks used to render transparency of wall tiles. */
-static DWORD WallMask[TILE_HEIGHT] = {
+const DWORD WallMask[TILE_HEIGHT] = {
 	0xAAAAAAAA,
 	0x55555555,
 	0xAAAAAAAA,
@@ -229,7 +231,7 @@ static DWORD WallMask[TILE_HEIGHT] = {
 	0x55555555
 };
 /** Fully opaque mask */
-static DWORD SolidMask[TILE_HEIGHT] = {
+const DWORD SolidMask[TILE_HEIGHT] = {
 	0xFFFFFFFF,
 	0xFFFFFFFF,
 	0xFFFFFFFF,
@@ -264,7 +266,7 @@ static DWORD SolidMask[TILE_HEIGHT] = {
 	0xFFFFFFFF
 };
 /** Used to mask out the left half of the tile diamond and only render additional content */
-static DWORD RightFoliageMask[TILE_HEIGHT] = {
+const DWORD RightFoliageMask[TILE_HEIGHT] = {
 	0xFFFFFFFF,
 	0x3FFFFFFF,
 	0x0FFFFFFF,
@@ -299,7 +301,7 @@ static DWORD RightFoliageMask[TILE_HEIGHT] = {
 	0x00000000,
 };
 /** Used to mask out the left half of the tile diamond and only render additional content */
-static DWORD LeftFoliageMask[TILE_HEIGHT] = {
+const DWORD LeftFoliageMask[TILE_HEIGHT] = {
 	0xFFFFFFFF,
 	0xFFFFFFFC,
 	0xFFFFFFF0,
@@ -334,7 +336,7 @@ static DWORD LeftFoliageMask[TILE_HEIGHT] = {
 	0x00000000,
 };
 
-inline static int count_leading_zeros(DWORD mask)
+inline int count_leading_zeros(DWORD mask)
 {
 	// Note: This function assumes that the argument is not zero,
 	// which means there is at least one bit set.
@@ -372,23 +374,16 @@ void foreach_set_bit(DWORD mask, const F &f)
 	}
 }
 
-inline static void RenderLine(CelOutputBuffer out, int &x, int y, BYTE **src, int n, BYTE *tbl, DWORD mask)
+inline void DoRenderLine(BYTE *dst, BYTE *src, int n, BYTE *tbl, DWORD mask)
 {
-	BYTE *dst = out.at(x, y);
-#ifdef NO_OVERDRAW
-	if (y < SCREEN_Y || dst > out.end()) {
-		goto skip;
-	}
-#endif
-
 	if (mask == 0xFFFFFFFF) {                // Opaque line
 		if (light_table_index == lightmax) { // Complete darkness
 			memset(dst, 0, n);
 		} else if (light_table_index == 0) { // Fully lit
-			memcpy(dst, *src, n);
+			memcpy(dst, src, n);
 		} else { // Partially lit
 			for (int i = 0; i < n; i++) {
-				dst[i] = tbl[(*src)[i]];
+				dst[i] = tbl[src[i]];
 			}
 		}
 	} else {
@@ -410,34 +405,42 @@ inline static void RenderLine(CelOutputBuffer out, int &x, int y, BYTE **src, in
 			} else if (light_table_index == 0) { // Fully lit
 				for (int i = 0; i < n; i++, mask <<= 1) {
 					if (mask & 0x80000000)
-						dst[i] = (*src)[i];
+						dst[i] = src[i];
 					else
-						dst[i] = paletteTransparencyLookup[dst[i]][(*src)[i]];
+						dst[i] = paletteTransparencyLookup[dst[i]][src[i]];
 				}
 			} else { // Partially lit
 				for (int i = 0; i < n; i++, mask <<= 1) {
 					if (mask & 0x80000000)
-						dst[i] = tbl[(*src)[i]];
+						dst[i] = tbl[src[i]];
 					else
-						dst[i] = paletteTransparencyLookup[dst[i]][tbl[(*src)[i]]];
+						dst[i] = paletteTransparencyLookup[dst[i]][tbl[src[i]]];
 				}
 			}
 		} else {                                 // Stippled transparancy
 			if (light_table_index == lightmax) { // Complete darkness
 				foreach_set_bit(mask, [=](int i) { dst[i] = 0; });
 			} else if (light_table_index == 0) { // Fully lit
-				foreach_set_bit(mask, [=](int i) { dst[i] = (*src)[i]; });
+				foreach_set_bit(mask, [=](int i) { dst[i] = src[i]; });
 			} else { // Partially lit
-				foreach_set_bit(mask, [=](int i) { dst[i] = tbl[(*src)[i]]; });
+				foreach_set_bit(mask, [=](int i) { dst[i] = tbl[src[i]]; });
 			}
 		}
 	}
+}
 
-skip:
+DVL_ATTRIBUTE_ALWAYS_INLINE
+inline void RenderLine(BYTE *dst_begin, BYTE *dst_end, BYTE **dst, BYTE **src, int n, BYTE *tbl, DWORD mask) {
+#ifdef NO_OVERDRAW
+	if (*dst >= dst_begin && *dst <= dst_end)
+#endif
+		DoRenderLine(*dst, *src, n, tbl, mask);
 	(*src) += n;
-	x += n;
+	(*dst) += n;
 }
 
+} // namespace
+
 #if defined(__clang__) || defined(__GNUC__)
 __attribute__((no_sanitize("shift-base")))
 #endif
@@ -447,7 +450,8 @@ void RenderTile(CelOutputBuffer out, int x, int y)
 	int i, j;
 	char c, v, tile;
 	BYTE *src, *tbl;
-	DWORD m, *mask, *pFrameTable;
+	DWORD m, *pFrameTable;
+	const DWORD *mask;
 
 	pFrameTable = (DWORD *)pDungeonCels;
 
@@ -501,68 +505,72 @@ void RenderTile(CelOutputBuffer out, int x, int y)
 	}
 #endif
 
+	BYTE *dst_begin = out.at(0, SCREEN_Y);
+	BYTE *dst_end = out.end();
+	BYTE *dst = out.at(x, y);
+	const int dst_pitch = out.pitch();
 	switch (tile) {
 	case RT_SQUARE:
-		for (i = TILE_HEIGHT; i != 0; --i, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2, tbl, *mask);
+		for (i = TILE_HEIGHT; i != 0; i--, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2, tbl, *mask);
 		}
 		break;
 	case RT_TRANSPARENT:
-		for (i = TILE_HEIGHT; i != 0; --i, --y, x -= TILE_WIDTH / 2, mask--) {
+		for (i = TILE_HEIGHT; i != 0; i--, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
 			m = *mask;
 			for (j = TILE_WIDTH / 2; j != 0; j -= v, v == TILE_WIDTH / 2 ? m = 0 : m <<= v) {
 				v = *src++;
 				if (v >= 0) {
-					RenderLine(out, x, y, &src, v, tbl, m);
+					RenderLine(dst_begin, dst_end, &dst, &src, v, tbl, m);
 				} else {
 					v = -v;
-					x += v;
+					dst += v;
 				}
 			}
 		}
 		break;
 	case RT_LTRIANGLE:
-		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, --y, x -= TILE_WIDTH / 2, mask--) {
+		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
 			src += i & 2;
-			x += i;
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+			dst += i;
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 		}
-		for (i = 2; i != TILE_WIDTH / 2; i += 2, --y, x -= TILE_WIDTH / 2, mask--) {
+		for (i = 2; i != TILE_WIDTH / 2; i += 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
 			src += i & 2;
-			x += i;
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+			dst += i;
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 		}
 		break;
 	case RT_RTRIANGLE:
-		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 			src += i & 2;
-			x += i;
+			dst += i;
 		}
-		for (i = 2; i != TILE_HEIGHT; i += 2, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+		for (i = 2; i != TILE_HEIGHT; i += 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 			src += i & 2;
-			x += i;
+			dst += i;
 		}
 		break;
 	case RT_LTRAPEZOID:
-		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, --y, x -= TILE_WIDTH / 2, mask--) {
+		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
 			src += i & 2;
-			x += i;
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+			dst += i;
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 		}
-		for (i = TILE_HEIGHT / 2; i != 0; --i, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2, tbl, *mask);
+		for (i = TILE_HEIGHT / 2; i != 0; i--, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2, tbl, *mask);
 		}
 		break;
 	case RT_RTRAPEZOID:
-		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2 - i, tbl, *mask);
+		for (i = TILE_HEIGHT - 2; i >= 0; i -= 2, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2 - i, tbl, *mask);
 			src += i & 2;
-			x += i;
+			dst += i;
 		}
-		for (i = TILE_HEIGHT / 2; i != 0; i--, --y, x -= TILE_WIDTH / 2, mask--) {
-			RenderLine(out, x, y, &src, TILE_WIDTH / 2, tbl, *mask);
+		for (i = TILE_HEIGHT / 2; i != 0; i--, dst -= dst_pitch + TILE_WIDTH / 2, mask--) {
+			RenderLine(dst_begin, dst_end, &dst, &src, TILE_WIDTH / 2, tbl, *mask);
 		}
 		break;
 	}
diff --git a/defs.h b/defs.h
index e7a532742..bae3e0a75 100644
--- a/defs.h
+++ b/defs.h
@@ -200,3 +200,15 @@
 #define strcasecmp _stricmp
 #define strncasecmp _strnicmp
 #endif
+
+#ifdef __has_attribute
+#define DVL_HAVE_ATTRIBUTE(x) __has_attribute(x)
+#else
+#define DVL_HAVE_ATTRIBUTE(x) 0
+#endif
+
+#if DVL_HAVE_ATTRIBUTE(always_inline) ||  (defined(__GNUC__) && !defined(__clang__))
+#define DVL_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
+#else
+#define DVL_ATTRIBUTE_ALWAYS_INLINE
+#endif