Fix scalar to array conversion for tessellation factors (#7837)

* Fix scalar to array conversion for tessellation factors in GLSL legalization

Add scalar-to-array conversion support in adaptType() function to handle
cases where users declare scalar tessellation factors (e.g., float TessLevelInner)
but GLSL requires arrays (float[2] for gl_TessLevelInner). This prevents the
generation of BuiltinCast instructions that crash the SPIR-V emitter.

Fixes crash: "unimplemented: Unhandled local inst in spirv-emit: BuiltinCast"

- Add scalar-to-array case in slang-ir-glsl-legalize.cpp adaptType()
- Fill all array elements with the scalar value for tessellation factors
- Add test case for scalar tessellation factor conversion

Fixes #7000

Co-authored-by: Yong He <csyonghe@users.noreply.github.com>

* Apply review feedback fixes

- Change test directive to TEST:SIMPLE
- Use IRArrayType instead of IRArrayTypeBase
- Use MakeArrayFromElement for cleaner scalar-to-array conversion

Co-authored-by: Yong He <csyonghe@users.noreply.github.com>

* Fix type conversion in scalar-to-array tessellation factor conversion

Convert scalar value to array element type before creating array to handle
cases where scalar type differs from array element type (e.g., int to float[3]).

Co-authored-by: Yong He <csyonghe@users.noreply.github.com>

* Use CHECK-DAG for order-independent tessellation factor checks

Co-authored-by: Yong He <csyonghe@users.noreply.github.com>

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Yong He <csyonghe@users.noreply.github.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/source/slang/slang-ir-glsl-legalize.cpp b/source/slang/slang-ir-glsl-legalize.cpp
index f001384a4..ac4d5c336 100644
--- a/source/slang/slang-ir-glsl-legalize.cpp
+++ b/source/slang/slang-ir-glsl-legalize.cpp
@@ -2094,6 +2094,18 @@ ScalarizedVal adaptType(IRBuilder* builder, IRInst* val, IRType* toType, IRType*
             }
         }
     }
+    else if (auto toArray = as<IRArrayType>(toType))
+    {
+        // Handle scalar-to-array conversion for tessellation factors
+        if (as<IRBasicType>(fromType))
+        {
+            // Convert the scalar value to the array's element type first
+            auto arrayElementType = toArray->getElementType();
+            auto convertedVal = builder->emitCast(arrayElementType, val);
+            val = builder->emitMakeArrayFromElement(toType, convertedVal);
+            return ScalarizedVal::value(val);
+        }
+    }
     // TODO: actually consider what needs to go on here...
     return ScalarizedVal::value(builder->emitCast(toType, val));
 }