[Git][freetype/freetype][master] [smooth] Fix left shifts of negative numbers.

[Werner Lemberg (@wl)]

Werner Lemberg pushed to branch master at FreeType / FreeType

Commits:

• 6be8bfe4
  by Werner Lemberg at 2021-08-06T08:31:22+02:00

  [smooth] Fix left shifts of negative numbers.
  
  Reported as
  
    https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36241
  
  * src/smooth/ftgrays.c (LEFT_SHIFT): New macro.
  (gray_render_conic) [BEZIER_USE_DDA]: Use it.
  

1 changed file:

• src/smooth/ftgrays.c

Changes:

src/smooth/ftgrays.c

---

...	...	@@ -1035,6 +1035,9 @@ typedef ptrdiff_t FT_PtrDist;
1035	1035	# include <emmintrin.h>
1036	1036	#endif
1037	1037
	1038	+#define LEFT_SHIFT( a, b ) (FT_Int64)( (FT_UInt64)(a) << (b) )
	1039	+
	1040	+
1038	1041	static void
1039	1042	gray_render_conic( RAS_ARG_ const FT_Vector* control,
1040	1043	const FT_Vector* to )
...	...	@@ -1126,13 +1129,15 @@ typedef ptrdiff_t FT_PtrDist;
1126	1129	* EMIT(P)
1127	1130	*
1128	1131	* To ensure accurate results, perform computations on 64-bit
1129		- * values, after scaling them by 2^32:
	1132	+ * values, after scaling them by 2^32.
	1133	+ *
	1134	+ * h = 1 / 2^N
1130	1135	*
1131		- * R << 32 = 2 * A << (32 - N - N)
1132		- * = A << (33 - 2 *N)
	1136	+ * R << 32 = 2 * A << (32 - N - N)
	1137	+ * = A << (33 - 2*N)
1133	1138	*
1134		- * Q << 32 = (2 * B << (32 - N)) + (A << (32 - N - N))
1135		- * = (B << (33 - N)) + (A << (32 - N - N))
	1139	+ * Q << 32 = (2 * B << (32 - N)) + (A << (32 - N - N))
	1140	+ * = (B << (33 - N)) + (A << (32 - 2*N))
1136	1141	*/
1137	1142
1138	1143	#ifdef __SSE2__
...	...	@@ -1199,14 +1204,14 @@ typedef ptrdiff_t FT_PtrDist;
1199	1204	bx = p1.x - p0.x;
1200	1205	by = p1.y - p0.y;
1201	1206
1202		- rx = ax << ( 33 - 2 * shift );
1203		- ry = ay << ( 33 - 2 * shift );
	1207	+ rx = LEFT_SHIFT( ax, 33 - 2 * shift );
	1208	+ ry = LEFT_SHIFT( ay, 33 - 2 * shift );
1204	1209
1205		- qx = ( bx << ( 33 - shift ) ) + ( ax << ( 32 - 2 * shift ) );
1206		- qy = ( by << ( 33 - shift ) ) + ( ay << ( 32 - 2 * shift ) );
	1210	+ qx = LEFT_SHIFT( bx, 33 - shift ) + LEFT_SHIFT( ax, 32 - 2 * shift );
	1211	+ qy = LEFT_SHIFT( by, 33 - shift ) + LEFT_SHIFT( ay, 32 - 2 * shift );
1207	1212
1208		- px = (FT_Int64)p0.x << 32;
1209		- py = (FT_Int64)p0.y << 32;
	1213	+ px = LEFT_SHIFT( p0.x, 32 );
	1214	+ py = LEFT_SHIFT( p0.y, 32 );
1210	1215
1211	1216	for ( count = 1U << shift; count > 0; count-- )
1212	1217	{

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