Driver issues

#1157 - Varying structs

• Description: Using varying structs can cause shader errors.
• Workaround: Not use structs for varyings.
• OS: Windows (GL and ANGLE)
• Vendors: Intel, Nvidia
• Driver versions: NVIDIA 381.65, ???
• See also: Issue#1136

Servo#13953 - Mac glsl compiler bug.

• Description: GLSL complier fails to parse the function get_fetch_uv in prim_shared.glsl.
• Workaround: This particular function was turned into a #define macro.
• OS: Mac
• Vendors:Intel
• Driver versions: Intel Iris 6100, Intel HD 5300, Intel HD 6000

??? - Mac glsl compiler bug realted to logical operators in #if blocks.

• Description: Found the diff but not the detailed issue. Most likely a shader compiler error with logical opertors in #if conditions like #if FOO == 1 && BAR == 1.
• Workaround: Nest #if blocks instead.
• OS: Mac
• Vendors: ???
• Driver versions: ???

#105 - Inset shadow with border radius crash

• Workaround: issue, accidentally fixed, we don't know how.
• OS: Mac

#650 - Terrible performance of sub-texture uploads on some mobile devices.

• Description: glTexSubImage is extremely slow on some devices (usually old ones).
• Workaround: None (maybe driver blocklist?).
• OS: Android
• Devices: SGX540, SGX530, Adreno200, Adreno205, (...)

#1242 - Shader compilation performance

• Description: Some shader compilers appear to aggressively inline some function calls, likely generating verbose internal representation of the code which causes compile times to go up.
• OS: ??
• Workaround: The following pattern:

switch foo
    case bar:
        do_the_thing(1);
        break;
    case baz:
        do_the_thing(2);
        break;
    case fun:
        do_the_thing(3);
        break;
}

Can be re-written into:

int param = 0;
switch foo
    case bar:
        param = 1;
        break;
    case baz:
        param = 2;
        break;
    case fun:
        param = 3;
        break;
}
do_the_thing(param);