sksl/shared/SwizzleIndexLookup.sksl

uniform half4 colorGreen, colorRed;
uniform float3x3 testMatrix3x3;
uniform float4x4 testMatrix4x4;

bool test3x3() {
    float3 expected = float3(3, 2, 1);
    for (int c=0; c<3; ++c) {
        float3 vec = testMatrix3x3[c];
        for (int r=0; r<3; ++r) {
            if (vec.zyx[r] != expected[r]) {
                return false;
            }
        }
        expected += 3;
    }
    return true;
}

bool test4x4() {
    float4 expected = float4(4, 3, 2, 1);
    for (int c=0; c<4; ++c) {
        float4 vec = testMatrix4x4[c];
        for (int r=0; r<4; ++r) {
            if (vec.wzyx[r] != expected[r]) {
                return false;
            }
        }
        expected += 4;
    }
    return true;
}

half4 main(float2 coords) {
    return test3x3() && test4x4() ? colorGreen : colorRed;
}