diff options
Diffstat (limited to 'src/core')
-rw-r--r-- | src/core/SkRasterPipeline.h | 34 |
1 files changed, 5 insertions, 29 deletions
diff --git a/src/core/SkRasterPipeline.h b/src/core/SkRasterPipeline.h index f1a3ef70d6..a4175c65a8 100644 --- a/src/core/SkRasterPipeline.h +++ b/src/core/SkRasterPipeline.h @@ -27,38 +27,14 @@ struct SkJumper_constants; * end up bloating our code size dramatically. SkRasterPipeline stages can be chained together * at runtime, so we can scale this problem linearly rather than combinatorically. * - * Each stage is represented by a function conforming to a common interface, SkRasterPipeline::Fn, - * and by an arbitrary context pointer. Fn's arguments, and sometimes custom calling convention, - * are designed to maximize the amount of data we can pass along the pipeline cheaply. - * On many machines all arguments stay in registers the entire time. + * Each stage is represented by a function conforming to a common interface and by an + * arbitrary context pointer. The stage funciton arguments and calling convention are + * designed to maximize the amount of data we can pass along the pipeline cheaply, and + * vary depending on CPU feature detection. * - * The meaning of the arguments to Fn are sometimes fixed: - * - The Stage* always represents the current stage, mainly providing access to ctx(). - * - The first size_t is always the destination x coordinate. - * (If you need y, put it in your context.) - * - The second size_t is always tail: 0 when working on a full 4-pixel slab, - * or 1..3 when using only the bottom 1..3 lanes of each register. - * - By the time the shader's done, the first four vectors should hold source red, - * green, blue, and alpha, up to 4 pixels' worth each. - * - * Sometimes arguments are flexible: - * - In the shader, the first four vectors can be used for anything, e.g. sample coordinates. - * - The last four vectors are scratch registers that can be used to communicate between - * stages; transfer modes use these to hold the original destination pixel components. - * - * On some platforms the last four vectors are slower to work with than the other arguments. - * - * When done mutating its arguments and/or context, a stage can either: - * 1) call st->next() with its mutated arguments, chaining to the next stage of the pipeline; or - * 2) return, indicating the pipeline is complete for these pixels. - * - * Some stages that typically return are those that write a color to a destination pointer, - * but any stage can short-circuit the rest of the pipeline by returning instead of calling next(). + * If you'd like to see how this works internally, you want to start digging around src/jumper. */ -// TODO: There may be a better place to stuff tail, e.g. in the bottom alignment bits of -// the Stage*. This mostly matters on 64-bit Windows where every register is precious. - #define SK_RASTER_PIPELINE_STAGES(M) \ M(callback) \ M(move_src_dst) M(move_dst_src) \ |