OPCODE_DISCARD unnecessary conversion of test parameter

[TiemoJung]

Hi,

the implementation of the OPCODE_DISCARD translation does forces the test parameter to be an int, but it should be a boolean as with all other compare operations.
As a result it turns

bool b;
if(b){discard;}

into

bool b;
if(int(b) * int(0xFFFFFFFFu)) != 0){discard;}

[arycama]

Any chance of getting this fixed? It is still an issue in Unity 2019.2. This has a noticeable effect on framerates, and seems like a huge oversight, especially as alpha-testing is already more expensive than usual on mobiles.

(Framerate impact mentioned in this thread)
https://forum.unity.com/threads/editing-compiled-shaders.515350/

[WeakKnight]

For metal, we can get it fixed by this patch: WeakKnight@c36a247