diff --git a/loopy/expression.py b/loopy/expression.py
index 5a11b8354..a00e4c7f0 100644
--- a/loopy/expression.py
+++ b/loopy/expression.py
@@ -162,9 +162,7 @@ def map_constant(self, expr: object) -> bool:
 
     def map_variable(self, expr: p.Variable) -> bool:
         if expr.name == self.vec_iname:
-            # Technically, this is doable. But we're not going there.
-            raise UnvectorizableError()
-
+            return True
         # A single variable is always a scalar.
         return False
 
diff --git a/loopy/symbolic.py b/loopy/symbolic.py
index 20ff55fea..2bdd8db70 100644
--- a/loopy/symbolic.py
+++ b/loopy/symbolic.py
@@ -606,6 +606,21 @@ class Literal(LoopyExpressionBase):
     s: str
 
 
+@p.expr_dataclass()
+class TypedLiteral(Literal):
+    """A literal to be used during code generation which we know the type of.
+
+    .. note::
+
+        Only used in the output of
+        :mod:`loopy.target.c.codegen.expression.ExpressionToCExpressionMapper` (and
+        similar mappers). Not for use in Loopy source representation.
+    """
+
+    s: str
+    dtype: ToLoopyTypeConvertible
+
+
 @p.expr_dataclass()
 class ArrayLiteral(LoopyExpressionBase):
     """An array literal.
diff --git a/loopy/target/c/codegen/expression.py b/loopy/target/c/codegen/expression.py
index 83c13dfe5..6b52256e9 100644
--- a/loopy/target/c/codegen/expression.py
+++ b/loopy/target/c/codegen/expression.py
@@ -49,7 +49,7 @@
 from loopy.expression import dtype_to_type_context
 from loopy.target.c import CExpression
 from loopy.type_inference import TypeInferenceMapper, TypeReader
-from loopy.types import LoopyType
+from loopy.types import LoopyType, to_loopy_type
 from loopy.typing import Expression, is_integer
 
 
@@ -435,7 +435,7 @@ def map_type_cast(self, expr: TypeCast, type_context: str):
         return self.rec(expr.child, type_context, expr.type)
 
     def map_constant(self, expr, type_context):
-        from loopy.symbolic import Literal
+        from loopy.symbolic import TypedLiteral
 
         if isinstance(expr, (complex, np.complexfloating)):
             real = self.rec(expr.real, type_context)
@@ -462,10 +462,10 @@ def map_constant(self, expr, type_context):
 
             # FIXME: This assumes a 32-bit architecture.
             if isinstance(expr, np.float32):
-                return Literal(repr(float(expr))+"f")
+                return TypedLiteral(repr(float(expr))+"f", to_loopy_type(np.float32))
 
             elif isinstance(expr, np.float64):
-                return Literal(repr(float(expr)))
+                return TypedLiteral(repr(float(expr)), to_loopy_type(np.float64))
 
             # Disabled for now, possibly should be a subtarget.
             # elif isinstance(expr, np.float128):
@@ -478,18 +478,19 @@ def map_constant(self, expr, type_context):
                     suffix += "u"
                 if iinfo.max > (2**31-1):
                     suffix += "l"
-                return Literal(repr(int(expr))+suffix)
+                return TypedLiteral(repr(int(expr))+suffix, to_loopy_type(iinfo.dtype))
             elif isinstance(expr, np.bool_):
-                return Literal("true") if expr else Literal("false")
+                return TypedLiteral("true", to_loopy_type(np.bool_)) if expr \
+                        else TypedLiteral("false", to_loopy_type(np.bool_))
             else:
                 raise LoopyError("do not know how to generate code for "
                         "constant of numpy type '%s'" % type(expr).__name__)
 
         elif np.isfinite(expr):
             if type_context == "f":
-                return Literal(repr(float(expr))+"f")
+                return TypedLiteral(repr(float(expr))+"f", to_loopy_type(np.float32))
             elif type_context == "d":
-                return Literal(repr(float(expr)))
+                return TypedLiteral(repr(float(expr)), to_loopy_type(np.float64))
             elif type_context in ["i", "b"]:
                 return int(expr)
             else:
diff --git a/loopy/target/ispc.py b/loopy/target/ispc.py
index 34a88328c..bcee0e905 100644
--- a/loopy/target/ispc.py
+++ b/loopy/target/ispc.py
@@ -44,13 +44,14 @@
     CoefficientCollector,
     CombineMapper,
     GroupHardwareAxisIndex,
-    Literal,
     LocalHardwareAxisIndex,
     SubstitutionMapper,
+    TypedLiteral,
     flatten,
 )
 from loopy.target.c import CFamilyASTBuilder, CFamilyTarget
 from loopy.target.c.codegen.expression import ExpressionToCExpressionMapper
+from loopy.types import to_loopy_type
 
 
 if TYPE_CHECKING:
@@ -125,10 +126,10 @@ def map_constant(self, expr, type_context):
             raise NotImplementedError("complex numbers in ispc")
         else:
             if type_context == "f":
-                return Literal(repr(float(expr)))
+                return TypedLiteral(repr(float(expr)), to_loopy_type(np.float32))
             elif type_context == "d":
                 # Keepin' the good ideas flowin' since '66.
-                return Literal(repr(float(expr))+"d")
+                return TypedLiteral(repr(float(expr))+"d", to_loopy_type(np.float64))
             elif type_context in ["i", "b"]:
                 return expr
             else:
diff --git a/loopy/target/opencl.py b/loopy/target/opencl.py
index 07c5b49d0..524ed7e6e 100644
--- a/loopy/target/opencl.py
+++ b/loopy/target/opencl.py
@@ -24,6 +24,7 @@
 THE SOFTWARE.
 """
 
+from contextlib import suppress
 from typing import TYPE_CHECKING, Literal, Sequence
 
 import numpy as np
@@ -46,6 +47,7 @@
 
     from loopy.codegen import CodeGenerationState
     from loopy.codegen.result import CodeGenerationResult
+    from loopy.kernel import LoopKernel
 
 
 # {{{ dtype registry wrappers
@@ -456,7 +458,8 @@ def get_opencl_callables():
 
 # {{{ symbol mangler
 
-def opencl_symbol_mangler(kernel, name):
+def opencl_symbol_mangler(kernel: LoopKernel,
+                          name: str) -> tuple[NumpyType, str] | None:
     # FIXME: should be more picky about exact names
     if name.startswith("FLT_"):
         return NumpyType(np.dtype(np.float32)), name
@@ -540,11 +543,32 @@ def opencl_preamble_generator(preamble_info):
 class ExpressionToOpenCLCExpressionMapper(ExpressionToCExpressionMapper):
 
     def wrap_in_typecast(self, actual_type, needed_dtype, s):
+
         if needed_dtype.dtype.kind == "b" and actual_type.dtype.kind == "f":
             # CL does not perform implicit conversion from float-type to a bool.
             from pymbolic.primitives import Comparison
             return Comparison(s, "!=", 0)
 
+        if needed_dtype == actual_type:
+            return s
+
+        registry = self.codegen_state.ast_builder.target.get_dtype_registry()
+        if self.codegen_state.target.is_vector_dtype(needed_dtype):
+            # OpenCL does not let you do explicit vector type casts between vector
+            # types. Instead you need to call their function which is of the form
+            # <desttype> convert_<desttype><n>(src) where n
+            # is the number of elements in the vector which is the same as in src.
+            # https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#explicit-casts
+
+            # We infer the data type of (s) before we recurse down into (s) to convert
+            # to a CExpression. With vectorization, we can change the actual type of (s)
+            # from a scalar type to a vector type. So we are going to recompute the
+            # actual type.
+            type_of_s = self.infer_type(s)
+            if self.codegen_state.target.is_vector_dtype(type_of_s):
+                cast = var("convert_%s" % registry.dtype_to_ctype(needed_dtype))
+                return cast(s)
+
         return super().wrap_in_typecast(actual_type, needed_dtype, s)
 
     def map_group_hw_index(self, expr, type_context):
@@ -553,6 +577,74 @@ def map_group_hw_index(self, expr, type_context):
     def map_local_hw_index(self, expr, type_context):
         return var("lid")(expr.axis)
 
+    def map_variable(self, expr, type_context):
+
+        if self.codegen_state.vectorization_info:
+            if self.codegen_state.vectorization_info.iname == expr.name:
+                # This needs to be converted into a vector literal.
+                from loopy.symbolic import TypedLiteral
+                vector_length = self.codegen_state.vectorization_info.length
+                index_type = self.codegen_state.kernel.index_dtype
+                vector_type = self.codegen_state.target.vector_dtype(index_type,
+                                                                     vector_length)
+                typename = self.codegen_state.target.dtype_to_typename(vector_type)
+                vector_literal = f"(({typename})" + " (" + \
+                        ",".join([f"{i}" for i in range(vector_length)]) + "))"
+                return TypedLiteral(vector_literal, vector_type)
+
+                # return Literal(vector_literal)
+        return super().map_variable(expr, type_context)
+
+    def map_if(self, expr, type_context):
+        from loopy.types import to_loopy_type
+        result_type = self.infer_type(expr)
+        conditional_needed_loopy_type = to_loopy_type(np.bool_)
+        if self.codegen_state.vectorization_info:
+            from loopy.codegen import UnvectorizableError
+            from loopy.expression import VectorizabilityChecker
+            checker = VectorizabilityChecker(self.codegen_state.kernel,
+                                     self.codegen_state.vectorization_info.iname,
+                                     self.codegen_state.vectorization_info.length)
+
+            with suppress(UnvectorizableError):
+                # We know there is an expression in codegen which can be vectorized.
+                # We are checking if this is one of the them. If it is not, then we can
+                # just continue with scalar code generation for this expression.
+                is_vector = checker(expr)
+
+                if is_vector:
+                    """
+                    We could have a vector literal here which may need to be
+                    converted to an appropriate size. The OpenCL specification states
+                    that for ( c ? a : b) a, b, and c must have the same
+                    number of elements and bits and that c must be an integral type.
+                    https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#table-builtin-relational
+                    """
+                    index_type = to_loopy_type(self.codegen_state.kernel.index_dtype)
+                    types = {8: to_loopy_type(np.int64), 4: to_loopy_type(np.int32),
+                             2: to_loopy_type(np.int16), 1: to_loopy_type(np.int8)}
+                    length = self.codegen_state.vectorization_info.length
+                    if self.codegen_state.target.is_vector_dtype(result_type):
+                        if (index_type.itemsize != result_type.itemsize and
+                            (result_type.itemsize // length) in types):
+                            index_type = types[result_type.itemsize]
+                        else:
+                            raise ValueError("Types incompatible")
+                    else:
+                        # We know result is going to be a vector.
+                        if (index_type.itemsize != result_type.itemsize and
+                            result_type.itemsize in types):
+                            index_type = types[result_type.itemsize]
+                    vector_type = self.codegen_state.target.vector_dtype(index_type,
+                                                                         length)
+                    conditional_needed_loopy_type = to_loopy_type(vector_type)
+
+        return type(expr)(
+                self.rec(expr.condition, type_context,
+                         conditional_needed_loopy_type),
+                self.rec(expr.then, type_context, result_type),
+                self.rec(expr.else_, type_context, result_type),
+                )
 # }}}
 
 
diff --git a/loopy/type_inference.py b/loopy/type_inference.py
index 8894af573..36ce49460 100644
--- a/loopy/type_inference.py
+++ b/loopy/type_inference.py
@@ -47,6 +47,7 @@
     SubArrayRef,
     SubstitutionRuleExpander,
     SubstitutionRuleMappingContext,
+    TypedLiteral,
     parse_tagged_name,
 )
 from loopy.translation_unit import (
@@ -365,6 +366,9 @@ def map_quotient(self, expr):
         else:
             return self.combine([n_dtype_set, d_dtype_set])
 
+    def map_typed_literal(self, expr: TypedLiteral):
+        return [expr.dtype]
+
     def map_constant(self, expr):
         if isinstance(expr, np.generic):
             return [NumpyType(np.dtype(type(expr)))]
@@ -540,19 +544,40 @@ def map_lookup(self, expr):
         dtype = field[0]
         return [NumpyType(dtype)]
 
+    def is_vector_dtype(self, dtype):
+        target = self.kernel.target
+
+        return target.is_vector_dtype(dtype)
+
     def map_comparison(self, expr):
-        self(expr.left, return_tuple=False, return_dtype_set=False)
-        self(expr.right, return_tuple=False, return_dtype_set=False)
+        left = self(expr.left, return_tuple=False, return_dtype_set=False)
+        right = self(expr.right, return_tuple=False, return_dtype_set=False)
+        # We need to return a vector type if we either of the sides is a vector.
+
+        vector_output = []
+        for dtype in (left, right):
+            if self.is_vector_dtype(dtype):
+                vector_output.append(dtype)
+        if vector_output:
+            return vector_output
         return [NumpyType(np.dtype(np.bool_))]
 
     def map_logical_not(self, expr):
-        self.rec(expr.child)
+        child = self.rec(expr.child)
+        if self.is_vector_dtype(child):
+            return child
 
         return [NumpyType(np.dtype(np.bool_))]
 
     def map_logical_and(self, expr):
+        output_type = []
         for child in expr.children:
-            self.rec(child)
+            type_to_check = self.rec(child)
+            if self.is_vector_dtype(type_to_check):
+                output_type.append(type_to_check)
+
+        if output_type:
+            return output_type
 
         return [NumpyType(np.dtype(np.bool_))]
 
diff --git a/test/test_target.py b/test/test_target.py
index fe2ad1d8a..76a38518d 100644
--- a/test/test_target.py
+++ b/test/test_target.py
@@ -875,6 +875,35 @@ def test_float3():
     assert "float3" in device_code
 
 
+def test_cl_vectorize_index_variable(ctx_factory):
+    knl = lp.make_kernel(
+            "{ [i]: 0<=i<n }",
+            """
+            b[i] = a[i]*3 if i < 32 else sin(a[i])
+            """)
+
+    knl = lp.split_array_axis(knl, "a,b", 0, 4)
+    knl = lp.split_iname(knl, "i", 4)
+    knl = lp.tag_inames(knl, {"i_inner": "vec", "i_outer": "for"})
+    knl = lp.tag_array_axes(knl, "a,b", "c,vec")
+    knl = lp.set_options(knl, write_code=True)
+    knl = lp.assume(knl, "n % 4 = 0 and n>0")
+
+    rng = np.random.default_rng(seed=12)
+    a = rng.normal(size=(16, 4))
+    ctx = ctx_factory()
+    queue = cl.CommandQueue(ctx)
+    knl = lp.add_and_infer_dtypes(knl, {"a": np.float64, "n": np.int64})
+    _evt, (result,) = knl(queue, a=a, n=a.size)
+
+    i = np.arange(16)
+    j = np.arange(4)
+    ind = 4*i[:, None] + j
+    result_ref = np.where(ind < 32, a*3, np.sin(a))
+
+    assert np.allclose(result, result_ref)
+
+
 if __name__ == "__main__":
     import sys
     if len(sys.argv) > 1: