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Thorough tests for saturatedAdd and mulDiv255Round.

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BUG=skia:3951

Committed: https://skia.googlesource.com/skia/+/ce9d11189a5924b47c3629063b72bae9d466c2c7

CQ_EXTRA_TRYBOTS=client.skia.android:Test-Android-GCC-Nexus5-CPU-NEON-Arm7-Release-Trybot

Review URL: https://codereview.chromium.org/1184113003
This commit is contained in:
mtklein 2015-06-15 10:58:42 -07:00 committed by Commit bot
parent 07a8fc827b
commit 3747875341
2 changed files with 37 additions and 1 deletions
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2
src/core/SkNx.h
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@ -184,7 +184,7 @@ public:
SkNi saturatedAdd(const SkNi& o) const {
SkASSERT((T)(~0) > 0); // TODO: support signed T
T sum = fVal + o.fVal;
return SkNi(sum > fVal ? sum : (T)(~0));
return SkNi(sum < fVal ? (T)(~0) : sum);
}
SkNi operator + (const SkNi& o) const { return SkNi(fVal + o.fVal); }

36
tests/SkNxTest.cpp
View File

@ -5,6 +5,7 @@
* found in the LICENSE file.
*/
#include "Sk4px.h"
#include "SkNx.h"
#include "SkRandom.h"
#include "Test.h"
@ -154,3 +155,38 @@ DEF_TEST(SkNi_min, r) {
}}
#endif
}
DEF_TEST(SkNi_saturatedAdd, r) {
for (int a = 0; a < (1<<8); a++) {
for (int b = 0; b < (1<<8); b++) {
int exact = a+b;
if (exact > 255) { exact = 255; }
if (exact < 0) { exact = 0; }
REPORTER_ASSERT(r, Sk16b(a).saturatedAdd(Sk16b(b)).kth<0>() == exact);
}
}
}
DEF_TEST(Sk4px_muldiv255round, r) {
for (int a = 0; a < (1<<8); a++) {
for (int b = 0; b < (1<<8); b++) {
int exact = (a*b+127)/255;
// Duplicate a and b 16x each.
Sk4px av((SkAlpha)a),
bv((SkAlpha)b);
// This way should always be exactly correct.
int correct = av.mulWiden(bv).div255RoundNarrow().kth<0>();
REPORTER_ASSERT(r, correct == exact);
// We're a bit more flexible on this method: correct for 0 or 255, otherwise off by <=1.
int fast = av.fastMulDiv255Round(bv).kth<0>();
REPORTER_ASSERT(r, fast-exact >= -1 && fast-exact <= 1);
if (a == 0 || a == 255 || b == 0 || b == 255) {
REPORTER_ASSERT(r, fast == exact);
}
}
}
}