Basic IR support for `static const` globals (#404)

* Basic IR support for `static const` globals

Our strategy for lowering global *variables* can fall back to putting their initialization into a function, but that isn't really appropriate for global constants (it also isn't appropriate for arrays, but we'll need to deal with that seaprately).

This change adds a distinct case for global constants (rather than treating them as variables), and forces the emission logic to always emit them as a single expression.
Doing this makes assumptions about how the IR for these constants gets emitted (and what optimziations might do to it).
In order to make things work, I had to switch the handling of initializer-list expressions to not be lowered via temporaries and mutation (since that isn't a good fit for reverting to a single expression).

I've added a single test case to ensure that this works in the simplest scenario. My next priority will be to see if this unblocks my work in Falcor.

* Fixup: bug fixes

1 files changed, 1 insertions, 0 deletions

diff --git a/source/slang/ir-ssa.cpp b/source/slang/ir-ssa.cpp
index 8a2d201dd..d58fd22e4 100644
--- a/source/slang/ir-ssa.cpp
+++ b/source/slang/ir-ssa.cpp
@@ -857,6 +857,7 @@ void constructSSA(IRModule* module, IRGlobalValue* globalVal)
     {
     case kIROp_Func:
     case kIROp_global_var:
+    case kIROp_global_constant:
         constructSSA(module, (IRGlobalValueWithCode*)globalVal);
 
     default: