Fix SPIRV `OpSpecConstantOp` emit (#7158)

* Fix SPIRV specialization constant with floating-point operations

* Improve test

* WIP

* Restrict `OpSpecConstantOp` allowed operations based on SPIRV specifications

* Fix typo on floating type check

* Emit error on float to int spec cosnt int val casts

1 files changed, 14 insertions, 1 deletions

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 205575a81..9472138c3 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1980,8 +1980,21 @@ IntVal* SemanticsVisitor::tryConstantFoldDeclRef(
          decl->hasModifier<VkConstantIdAttribute>()) &&
         kind == ConstantFoldingKind::SpecializationConstant)
     {
+        // Float-to-inst casts cannot be`OpSpecConstOp` operations in SPIR-V,
+        // which means they need to be local instructions can cannot be hoisted to the
+        // global scope. Deduplication logic is run for `IntVal`s however and without hoisting
+        // instructions using this `IntVal` will trigger error. Hence we emit error here
+        // to not allow such cases.
+        //
+        // Note that float-to-inst casts for non-`IntVal`s are allowed.
+        if (!isScalarIntegerType(decl->getType()))
+        {
+            getSink()->diagnose(declRef, Diagnostics::intValFromNonIntSpecConstEncountered);
+            return nullptr;
+        }
+
         return m_astBuilder->getOrCreate<DeclRefIntVal>(
-            declRef.substitute(m_astBuilder, declRef.getDecl()->getType()),
+            declRef.substitute(m_astBuilder, decl->getType()),
             declRef);
     }