[Webkit-unassigned] [Bug 235478] WebGL enabling Blend causes high performance drop

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=235478

--- Comment #4 from Reinis <muiznieks.reinis at gmail.com> ---
The 30 FPS limit I noticed before was because the console was open. Didn't know before that it affects it.

Seems like I found the issue..

* Causes lag
```
int textureIdx = textureId - 1;
vec2 animatedUv = fUv + textureOffsets[textureIdx];
```

* Causes lag
```
int textureIdx = textureId - 1;
if (textureIdx > 127) {
    c = Color;
    return;
}
vec2 animatedUv = fUv + textureOffsets[textureIdx];
```

* Doesn't lag
```
int textureIdx = textureId - 1;
vec2 animatedUv = fUv + textureOffsets[1];
```

* Doesn't lag
```
int textureIdx = 1;
vec2 animatedUv = fUv + textureOffsets[textureIdx];
```


* Doesn't lag
```
int textureIdx = textureId - 1;
vec2 animatedUv = fUv;
```

I did a bit more experiments, but it seems that using `flat in int textureId;` as an index in `uniform vec2 textureOffsets[128];` causes lag.

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