By default, the matrix would be declared as mediump, causing precision
issues. Need to dispatch to two separate functions since GLSL does not
support overload based on precision.
HLSL is very fussy about fallthrough in switch blocks, so promote
Unreachable blocks to breaks if they are inside a switch construct.
Some false positives are possible in weird multi-break scenarios, but
this is benign.
We have been interchanging spv and SPIRV_Cross_ for a while, which
causes weirdness since we don't explicitly ban SPIRV_Cross identifiers,
as these identifiers are generally used for interface variable
workarounds.
This subtle bug removed any expression validation for trivially swizzled
variables. Make usage suppression a more explicit concept rather than
just hacking off forwarded_temporaries.
There is some fallout here with loop generation since our expression
invalidation is currently a bit too naive to handle loops properly.
The forwarding bug masked this problem until now.
If part of the loop condition is also used in the body, we end up
reading an invalid expression, which in turn forces a temporary to be
generated in the condition block, not good. We'll need to be smarter
here ...
