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simplify skvm blitter main logic

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A lot of this careful load-this-now logic is moot given the data flow
and scheduling that skvm has been doing for the last few months.  We can
write all this in simple unconditional canonical order now and it'll be
reordered, dead code eliminated, strength reduced, etc. as possible.

One really big simplification is that we can always notionally load and
apply coverage and let skvm handle whether or not it is really needed:
when coverage is known to be splat(1.0f), the pre-blend multiplies drop
away, and now that lerp() is a little smarter, the post-blend lerp()s
drop away too.

Change-Id: I0534b484bf927ef315335c991704ed52bb6010d5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308917
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
This commit is contained in:
Mike Klein 2020-08-08 11:03:03 -05:00 committed by Skia Commit-Bot
parent 18423cd5b3
commit fff62bb44a
1 changed files with 58 additions and 78 deletions
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136
src/core/SkVMBlitter.cpp
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@ -241,90 +241,68 @@ namespace {
src_in_gamut = true;
}
// There are several orderings here of when we load dst and coverage
// and how coverage is applied, and to complicate things, LCD coverage
// needs to know dst.a. We're careful to assert it's loaded in time.
skvm::Color dst;
SkDEBUGCODE(bool dst_loaded = false;)
// load_coverage() returns false when there's no need to apply coverage.
auto load_coverage = [&](skvm::Color* cov) {
bool partial_coverage = true;
switch (params.coverage) {
case Coverage::Full: cov->r = cov->g = cov->b = cov->a = p->splat(1.0f);
partial_coverage = false;
break;
case Coverage::UniformA8: cov->r = cov->g = cov->b = cov->a =
from_unorm(8, p->uniform8(p->uniform(), 0));
break;
case Coverage::Mask3D:
case Coverage::MaskA8: cov->r = cov->g = cov->b = cov->a =
from_unorm(8, p->load8(p->varying<uint8_t>()));
break;
case Coverage::MaskLCD16: {
SkASSERT(dst_loaded);
skvm::PixelFormat fmt;
SkAssertResult(SkColorType_to_PixelFormat(kRGB_565_SkColorType, &fmt));
*cov = p->load(fmt, p->varying<uint16_t>());
cov->a = select(src.a < dst.a, min(cov->r, min(cov->g, cov->b))
, max(cov->r, max(cov->g, cov->b)));
} break;
}
if (params.clip) {
skvm::Color clip = as_SB(params.clip)->program(p, device,local, paint,
params.matrices, /*localM=*/nullptr,
params.quality, params.dst,
uniforms, alloc);
SkAssertResult(clip);
cov->r *= clip.a; // We use the alpha channel of clip for all four.
cov->g *= clip.a;
cov->b *= clip.a;
cov->a *= clip.a;
return true;
}
return partial_coverage;
};
// The math for some blend modes lets us fold coverage into src before the blend,
// obviating the need for the lerp afterwards. This early-coverage strategy tends
// to be both faster and require fewer registers.
bool lerp_coverage_post_blend = true;
if (SkBlendMode_ShouldPreScaleCoverage(params.blendMode,
params.coverage == Coverage::MaskLCD16)) {
skvm::Color cov;
if (load_coverage(&cov)) {
src.r *= cov.r;
src.g *= cov.g;
src.b *= cov.b;
src.a *= cov.a;
}
lerp_coverage_post_blend = false;
}
// Load up the destination color.
SkDEBUGCODE(dst_loaded = true;)
skvm::PixelFormat pixelFormat;
SkAssertResult(SkColorType_to_PixelFormat(params.dst.colorType(), &pixelFormat));
dst = p->load(pixelFormat, dst_ptr);
// When a destination is known opaque, we may assume it both starts and stays fully
// opaque, ignoring any math that disagrees. This sometimes trims a little work.
// Load the destination color.
skvm::PixelFormat dstFormat;
SkAssertResult(SkColorType_to_PixelFormat(params.dst.colorType(), &dstFormat));
skvm::Color dst = p->load(dstFormat, dst_ptr);
if (params.dst.isOpaque()) {
// When a destination is known opaque, we may assume it both starts and stays fully
// opaque, ignoring any math that disagrees. This sometimes trims a little work.
dst.a = p->splat(1.0f);
} else if (params.dst.alphaType() == kUnpremul_SkAlphaType) {
// All our blending works in terms of premul.
dst = premul(dst);
}
src = blend(params.blendMode, src, dst);
// Load coverage.
skvm::Color cov;
switch (params.coverage) {
case Coverage::Full:
cov.r = cov.g = cov.b = cov.a = p->splat(1.0f);
break;
case Coverage::UniformA8:
cov.r = cov.g = cov.b = cov.a = from_unorm(8, p->uniform8(p->uniform(), 0));
break;
case Coverage::Mask3D:
case Coverage::MaskA8:
cov.r = cov.g = cov.b = cov.a = from_unorm(8, p->load8(p->varying<uint8_t>()));
break;
case Coverage::MaskLCD16: {
skvm::PixelFormat fmt;
SkAssertResult(SkColorType_to_PixelFormat(kRGB_565_SkColorType, &fmt));
cov = p->load(fmt, p->varying<uint16_t>());
cov.a = select(src.a < dst.a, min(cov.r, min(cov.g, cov.b))
, max(cov.r, max(cov.g, cov.b)));
} break;
}
if (params.clip) {
skvm::Color clip = as_SB(params.clip)->program(p, device,local, paint,
params.matrices, /*localM=*/nullptr,
params.quality, params.dst,
uniforms, alloc);
SkAssertResult(clip);
cov.r *= clip.a; // We use the alpha channel of clip for all four.
cov.g *= clip.a;
cov.b *= clip.a;
cov.a *= clip.a;
}
// The math for some blend modes lets us fold coverage into src before the blend,
// which is simpler than the canonical post-blend lerp().
if (SkBlendMode_ShouldPreScaleCoverage(params.blendMode,
params.coverage == Coverage::MaskLCD16)) {
src.r *= cov.r;
src.g *= cov.g;
src.b *= cov.b;
src.a *= cov.a;
src = blend(params.blendMode, src, dst);
} else {
src = blend(params.blendMode, src, dst);
// Lerp with coverage post-blend if needed.
if (skvm::Color cov; lerp_coverage_post_blend && load_coverage(&cov)) {
src.r = lerp(dst.r, src.r, cov.r);
src.g = lerp(dst.g, src.g, cov.g);
src.b = lerp(dst.b, src.b, cov.b);
@ -332,6 +310,7 @@ namespace {
}
if (params.dst.isOpaque()) {
// (See the note above when loading the destination color.)
src.a = p->splat(1.0f);
} else if (params.dst.alphaType() == kUnpremul_SkAlphaType) {
src = unpremul(src);
@ -355,7 +334,8 @@ namespace {
src.a = clamp01(src.a);
}
SkAssertResult(store(pixelFormat, dst_ptr, src));
// Write it out!
SkAssertResult(store(dstFormat, dst_ptr, src));
}