[smooth] Minor speedup to smooth rasterizer
This speeds up the smooth rasterizer by avoiding a
conditional branches in the hot path. Namely:
- Define a fixed "null cell" which will be pointed
to whenever the current cell is outside of the current
target region. This avoids a "ras.cell != NULL"
check in the FT_INTEGRATE() macro.
- Also use the null cell as a sentinel at the end of
all ycells[] linked-lists, by setting its x coordinate
to INT_MAX. This avoids a 'if (!cell)' check in
gray_set_cell() as well.
- Slightly change the worker struct fields to perform
a little less operations during rendering.
Example results (on a 2013 Corei5-3337U CPU)
out/ftbench -p -s10 -t5 -bc /usr/share/fonts/truetype/droid/DroidSansFallbackFull.ttf
Before: 5.472 us/op
After: 5.275 us/op
out/ftbench -p -s60 -t5 -bc /usr/share/fonts/truetype/droid/DroidSansFallbackFull.ttf
Before: 17.988 us/op
After: 17.389 us/op
diff --git a/ChangeLog b/ChangeLog
index c8a0795..1b8a647 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2021-07-13 David Turner <david@freetype.org>
+
+ [smooth] Minor speedup to smooth rasterizer
+
+ This speeds up the smooth rasterizer by avoiding a conditional
+ branches in the hot path.
+
+ * src/smooth/ftgrays.c: Define a null cell used to both as a
+ sentinel for all linked-lists, and to accumulate coverage and
+ area values for "out-of-bounds" cell positions without a
+ conditional check.
+
2021-07-13 Oleg Oshmyan <chortos@inbox.lv>
[base] Fix `FT_Open_Face`'s handling of user-supplied streams.
diff --git a/src/smooth/ftgrays.c b/src/smooth/ftgrays.c
index 60cd5e0..e66ec34 100644
--- a/src/smooth/ftgrays.c
+++ b/src/smooth/ftgrays.c
@@ -479,19 +479,24 @@
{
ft_jmp_buf jump_buffer;
- TCoord min_ex, max_ex;
+ TCoord min_ex, max_ex; /* min and max integer pixel coordinates */
TCoord min_ey, max_ey;
+ TCoord count_ey; /* same as (max_ey - min_ey) */
- PCell cell;
- PCell* ycells;
- PCell cells;
- FT_PtrDist max_cells;
- FT_PtrDist num_cells;
+ PCell cell; /* current cell */
+ PCell cell_free; /* call allocation next free slot */
+ PCell cell_limit; /* cell allocation limit */
- TPos x, y;
+ PCell* ycells; /* array of cell linked-lists, one per */
+ /* vertical coordinate in the current band. */
- FT_Outline outline;
- TPixmap target;
+ PCell cells; /* cell storage area */
+ FT_PtrDist max_cells; /* cell storage capacity */
+
+ TPos x, y; /* last point position */
+
+ FT_Outline outline; /* input outline */
+ TPixmap target; /* target pixmap */
FT_Raster_Span_Func render_span;
void* render_span_data;
@@ -502,21 +507,34 @@
#pragma warning( pop )
#endif
-
#ifndef FT_STATIC_RASTER
#define ras (*worker)
#else
static gray_TWorker ras;
#endif
-#define FT_INTEGRATE( ras, a, b ) \
- if ( ras.cell ) \
- ras.cell->cover += (a), ras.cell->area += (a) * (TArea)(b)
+/* Return a pointer to the "null cell", used as a sentinel at the end */
+/* of all ycells[] linked lists. Its x coordinate should be maximal */
+/* to ensure no NULL checks are necessary when looking for an insertion */
+/* point in gray_set_cell(). Other loops should check the cell pointer */
+/* with CELL_IS_NULL() to detect the end of the list. */
+#define NULL_CELL_PTR(ras) (ras).cells
+
+/* The |x| value of the null cell. Must be the largest possible */
+/* integer value stored in a TCell.x field. */
+#define CELL_MAX_X_VALUE INT_MAX
+
+/* Return true iff |cell| points to the null cell. */
+#define CELL_IS_NULL(cell) ((cell)->x == CELL_MAX_X_VALUE)
+
+
+#define FT_INTEGRATE( ras, a, b ) \
+ ras.cell->cover += (a), ras.cell->area += (a) * (TArea)(b)
typedef struct gray_TRaster_
{
- void* memory;
+ void* memory;
} gray_TRaster, *gray_PRaster;
@@ -538,7 +556,7 @@
printf( "%3d:", y );
- for ( ; cell != NULL; cell = cell->next )
+ for ( ; !CELL_IS_NULL(cell); cell = cell->next )
printf( " (%3d, c:%4d, a:%6d)",
cell->x, cell->cover, cell->area );
printf( "\n" );
@@ -566,11 +584,12 @@
/* Note that if a cell is to the left of the clipping region, it is */
/* actually set to the (min_ex-1) horizontal position. */
- if ( ey >= ras.max_ey || ey < ras.min_ey || ex >= ras.max_ex )
- ras.cell = NULL;
+ TCoord ey_index = ey - ras.min_ey;
+ if ( ey_index < 0 || ey_index >= ras.count_ey || ex >= ras.max_ex )
+ ras.cell = NULL_CELL_PTR(ras);
else
{
- PCell* pcell = ras.ycells + ey - ras.min_ey;
+ PCell* pcell = ras.ycells + ey_index;
PCell cell;
@@ -580,7 +599,7 @@
{
cell = *pcell;
- if ( !cell || cell->x > ex )
+ if ( cell->x > ex )
break;
if ( cell->x == ex )
@@ -589,11 +608,11 @@
pcell = &cell->next;
}
- if ( ras.num_cells >= ras.max_cells )
+ /* insert new cell */
+ cell = ras.cell_free++;
+ if (cell >= ras.cell_limit)
ft_longjmp( ras.jump_buffer, 1 );
- /* insert new cell */
- cell = ras.cells + ras.num_cells++;
cell->x = ex;
cell->area = 0;
cell->cover = 0;
@@ -1218,7 +1237,7 @@
unsigned char* line = ras.target.origin - ras.target.pitch * y;
- for ( ; cell != NULL; cell = cell->next )
+ for ( ; !CELL_IS_NULL(cell); cell = cell->next )
{
if ( cover != 0 && cell->x > x )
{
@@ -1266,7 +1285,7 @@
TArea area;
- for ( ; cell != NULL; cell = cell->next )
+ for ( ; !CELL_IS_NULL(cell); cell = cell->next )
{
if ( cover != 0 && cell->x > x )
{
@@ -1646,8 +1665,8 @@
FT_TRACE7(( "band [%d..%d]: %ld cell%s\n",
ras.min_ey,
ras.max_ey,
- ras.num_cells,
- ras.num_cells == 1 ? "" : "s" ));
+ ras.cell_free - ras.cells.,
+ ras.cell_free - ras.cells == 1 ? "" : "s" ));
}
else
{
@@ -1690,8 +1709,18 @@
ras.cells = buffer + n;
ras.max_cells = (FT_PtrDist)( FT_MAX_GRAY_POOL - n );
+ ras.cell_limit = ras.cells + ras.max_cells;
ras.ycells = (PCell*)buffer;
+ /* Initialize the null cell is at the start of the 'cells' array. */
+ /* Note that this requires ras.cell_free initialization to skip */
+ /* over the first entry in the array. */
+ PCell null_cell = NULL_CELL_PTR(ras);
+ null_cell->x = CELL_MAX_X_VALUE;
+ null_cell->area = 0;
+ null_cell->cover = 0;
+ null_cell->next = NULL;;
+
for ( y = yMin; y < yMax; )
{
ras.min_ey = y;
@@ -1705,15 +1734,17 @@
do
{
TCoord width = band[0] - band[1];
+ TCoord w;
int error;
+ for (w = 0; w < width; ++w)
+ ras.ycells[w] = null_cell;
- FT_MEM_ZERO( ras.ycells, height * sizeof ( PCell ) );
-
- ras.num_cells = 0;
- ras.cell = NULL;
+ ras.cell_free = ras.cells + 1; /* NOTE: Skip over the null cell. */
+ ras.cell = null_cell;
ras.min_ey = band[1];
ras.max_ey = band[0];
+ ras.count_ey = width;
error = gray_convert_glyph_inner( RAS_VAR, continued );
continued = 1;
