Fix for missing signedness cast in SwizzleIR (#7448)

* Cast if there is a signedness mismatch on the swizzle

* Move isSignedType to slang-util and add test

---------

Co-authored-by: Yong He <yonghe@outlook.com>

4 files changed, 31 insertions, 21 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index ec9857ecf..8e8e7327b 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -7763,27 +7763,6 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
             List<IRInst*>::makeRepeated(scalar, Index(numElems)));
     }
 
-    bool isSignedType(IRType* type)
-    {
-        switch (type->getOp())
-        {
-        case kIROp_FloatType:
-        case kIROp_DoubleType:
-            return true;
-        case kIROp_IntType:
-        case kIROp_Int16Type:
-        case kIROp_Int64Type:
-        case kIROp_Int8Type:
-            return true;
-        case kIROp_VectorType:
-            return isSignedType(as<IRVectorType>(type)->getElementType());
-        case kIROp_MatrixType:
-            return isSignedType(as<IRMatrixType>(type)->getElementType());
-        default:
-            return false;
-        }
-    }
-
     bool isFloatType(IRInst* type)
     {
         switch (type->getOp())
diff --git a/source/slang/slang-ir-util.cpp b/source/slang/slang-ir-util.cpp
index 13742711c..a2ec15661 100644
--- a/source/slang/slang-ir-util.cpp
+++ b/source/slang/slang-ir-util.cpp
@@ -2348,4 +2348,25 @@ bool isInstHoistable(IROp op, IRType* type, IRInst* const* fixedArgs)
            isSpecConstOpHoistable(op, type, fixedArgs);
 }
 
+bool isSignedType(IRType* type)
+{
+    switch (type->getOp())
+    {
+    case kIROp_FloatType:
+    case kIROp_DoubleType:
+        return true;
+    case kIROp_IntType:
+    case kIROp_Int16Type:
+    case kIROp_Int64Type:
+    case kIROp_Int8Type:
+        return true;
+    case kIROp_VectorType:
+        return isSignedType(as<IRVectorType>(type)->getElementType());
+    case kIROp_MatrixType:
+        return isSignedType(as<IRMatrixType>(type)->getElementType());
+    default:
+        return false;
+    }
+}
+
 } // namespace Slang
diff --git a/source/slang/slang-ir-util.h b/source/slang/slang-ir-util.h
index cccec7e05..dccdf5457 100644
--- a/source/slang/slang-ir-util.h
+++ b/source/slang/slang-ir-util.h
@@ -417,6 +417,8 @@ constexpr bool anyOf(Range&& range, Predicate&& pred)
     }
     return false;
 }
+
+bool isSignedType(IRType* type);
 } // namespace Slang
 
 #endif
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index a03c75d7d..df3507670 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -7855,6 +7855,14 @@ top:
                     // we simply form a pointer to each of the vector
                     // elements and write to them individually.
                     IRInst* irRightVal = getSimpleVal(context, right);
+
+                    // If there is a mismatch between the signedness of the left and rigth values
+                    // then emit a cast
+                    if (isSignedType(swizzleInfo->type) != isSignedType(irRightVal->getDataType()))
+                    {
+                        irRightVal = builder->emitCast(swizzleInfo->type, irRightVal);
+                    }
+
                     swizzledStore(
                         loweredBase.val,
                         irRightVal,