If this is computed *before* a `demote`, but used *after*, forwarding it
will produce the wrong value. This does make for uglier shaders, but
it's necessary right now to ensure correctness.
I needed to use an assembly shader to produce the test for this.
`spirv-opt` is not smart enough (or too smart?) to eliminate the
variable that would be used in GLSL to express this.
This extension provides a new operation which causes a fragment to be
discarded without terminating the fragment shader invocation. The
invocation for the discarded fragment becomes a helper invocation, so
that derivatives will remain defined. The old `HelperInvocation` builtin
becomes undefined when this occurs, so a second new instruction queries
the current helper invocation status.
This is only fully supported for GLSL. HLSL doesn't support the
`IsHelperInvocation` operation and MSL doesn't support the
`DemoteToHelperInvocation` op.
Fixes#1052.
Storage was in place already, so mostly just dealing with bitcasts and
constants.
Simplies some of the bitcasting logic, and this exposed some bugs in the
implementation. Refactor to use correct width integers with explicit bitcast opcodes.
The size of an array can be a specialization constant or a spec constant
op. This complicates things quite a lot.
Reflection becomes very painful in the presence of expressions instead
of literals so add a new array which expresses this.
It is unlikely that we will need to do accurate reflection of interface
types which have specialization constant size.
SSBOs and UBOs will for now throw exception if a dynamic size is used since it
is very difficult to know the real size.
This is now fixed in ESSL 3.10 backend of glslang, so we can remove the old workaround
of dropping full memory barriers.
Also fixes unrelated issue which newer glslang detects.
