Hello,

I am trying to perform 2D convolution on SGX530 with the following code:

```
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
uniform sampler2D texture0;
uniform sampler2D texture1;
uniform float w; // inverse dimension of the texture - necessary to not overflow floats
varying vec2 vTexCoord;
// same as above
vec4 pack(float value);
float unpack(vec4 texel);
void main(void)
{
const int kSpan = 3;
const int spread = kSpan / 2;
vec4 samp[kSpan * kSpan];
vec4 value;
// load the part of the image which will be used for convolution from texture memory
for (int i = -spread; i <= spread; ++i)
{
for (int j = -spread; j <= spread; ++j)
{
if ((vTexCoord.x + float(j) * w) > 1.0 ||
(vTexCoord.x + float(j) * w) < 0.0 ||
(vTexCoord.y + float(i) * w) > 1.0 ||
(vTexCoord.y + float(i) * w) < 0.0)
{
value = vec4(0.0);
}
else
{
value = texture2D(texture0, vTexCoord + vec2(float(j) * w, float(i) * w));
}
samp[(i + spread) * kSpan + (j + spread)] = value;
}
}
float result = 0.0;
float step = 1.0 / float (1 + kSpan); // how much step through the kernel texture
// do the convolution (dot product)
for (int i = 0; i < kSpan; ++i)
{
for (int j = 0; j < kSpan; ++j)
{
result += unpack(samp[i * kSpan + j] * 255.0) * unpack(texture2D(texture1, vec2(step * float(j + 1), step * float(i + 1))) * 255.0);
}
}
// do the last transformation to float
gl_FragColor = pack(result);
}
```

And the result is a warning from the compiler:

```
WARNING: 0:82: Calls to any function that may require a gradient calculation inside a conditional block may return undefined results
WARNING: 0:100: Calls to any function that may require a gradient calculation inside a conditional block may return undefined results
WARNING: 2 compilation warnings.
```

I searched for some answers but just found out this which mentions that I should replace the branches with a *mix* or *step* which I did, like this:

```
// load the part of the image which will be used for convolution from texture memory
for (int i = -spread; i <= spread; ++i)
{
for (int j = -spread; j <= spread; ++j)
{
float outside = float((vTexCoord.x + float(j) * w) > 1.0 ||
(vTexCoord.x + float(j) * w) < 0.0 ||
(vTexCoord.y + float(i) * w) > 1.0 ||
(vTexCoord.y + float(i) * w) < 0.0);
value = mix(texture2D(texture0, vTexCoord + vec2(float(j) * w, float(i) * w)), vec4(0), outside);
samp[(i + spread) * kSpan + (j + spread)] = value;
}
}
```

However it still complains about the branch. How would I circumvent the error and how can I see the generated assembly?