SPIR-V 1.6 added the LocalSizeId execution mode that allows using
spec constants for setting the work-group size, however it does not
deprecate the LocalSize mode. This change causes the LocalSizeId mode to
only be used when at least one of the workgroup size is actually
specified with a spec constant.
Fixes#3200
There are 3 separate tests added to cover the 3 cases in
visitSelection(). With SPIR-V versions prior to 1.4, control flow is
generated, with GLSL generating code to execute only the appropriate
branch of the conditional while HLSL executes both branches and uses the
control flow to select the appropriate one. Finally, with SPIR-V
versions newer than 1.4, OpSelect can be used on structs.
Note that the hlsl.structcopy.comp and hlsl.structcopylogical.comp tests
have identical shader code, but are compiled with different versions of
SPIR-V and result in different codepaths being used and different SPIR-V
generated.
