Fix GLSL static initialization bug. (#3409)

* Fix GLSL static initialization bug.

Fixes #3408.

* Update comment.

* Fold global var initializer as an expression if possible.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 4 insertions, 7 deletions

diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 146f54932..7621f3080 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -7661,23 +7661,20 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
             //
             //      if(!isInitialized) { <globalVal> = <initExpr>; isInitialized = true; }
             //
-            // TODO: we could conceivably optimize this by detecting
-            // when the `initExpr` lowers to just a reference to a constant,
-            // and then either deleting the extra code structure there,
-            // or not generating it in the first place. That is a bit
-            // more complexity than I'm ready for at the moment.
+            // This will generate a lot of boilterplate code, but we optimize out the
+            // boilerplate functions later during `moveGlobalVarInitializationToEntryPoints`
+            // if we see the init function is just returning a global constant.
             //
             auto boolBuilder = subBuilder;
 
             auto irBoolType = boolBuilder->getBoolType();
             auto irBool = boolBuilder->createGlobalVar(irBoolType);
             boolBuilder->setInsertInto(irBool);
-            boolBuilder->setInsertInto(boolBuilder->createBlock());
+            boolBuilder->emitBlock();
             boolBuilder->emitReturn(boolBuilder->getBoolValue(false));
 
             auto boolVal = LoweredValInfo::ptr(irBool);
 
-
             // Okay, with our global Boolean created, we can move on to
             // generating the code we actually care about, back in the original function.