[LANGUAGE] Added support for bitcast (#119)

include/triton/ir/dispatch.h

@@ -62,6 +62,7 @@ struct dispatch{
   static ir::value *reshape(ir::value *input, shape_t shape, ir::builder *builder);
   static ir::value *broadcast(ir::value *input, shape_t shape, ir::builder *builder);
   static std::tuple<ir::value*, ir::value*> broadcast(ir::value *lhs, ir::value* rhs, ir::builder *builder);
+  static ir::value *bitcast(ir::value *input, ir::type *type, ir::builder *builder);
   static ir::value *cast(ir::value *input, ir::type *type, ir::builder *builder);
 
   // memory operators

lib/ir/dispatch.cc

@@ -414,6 +414,23 @@ std::tuple<ir::value*, ir::value*> dispatch::broadcast(ir::value *lhs, ir::value
   return std::make_tuple(lhs, rhs);
 }
 
+ir::value *dispatch::bitcast(ir::value *input, ir::type *dst_ty, ir::builder *builder){
+  ir::type *src_ty = input->get_type();
+  if (src_ty->is_block_ty())
+    dst_ty = ir::block_type::get(dst_ty, input->get_type()->get_block_shapes());
+  if(src_ty == dst_ty)
+    return input;
+  ir::type *src_sca_ty = src_ty->get_scalar_ty();
+  ir::type *dst_sca_ty = dst_ty->get_scalar_ty();
+  // Bitcast
+  int src_bits = src_sca_ty->get_primitive_size_in_bits();
+  int dst_bits = dst_sca_ty->get_primitive_size_in_bits();
+  if( src_bits!= dst_bits)
+    throw std::runtime_error("Cannot bitcast data-type of size " + std::to_string(src_bits) +
+                             "to data-type of size " + std::to_string(dst_bits));
+  return builder->create_cast(ir::BitCast, input, dst_ty);
+}
+
 ir::value *dispatch::cast(ir::value *input, ir::type *dst_ty, ir::builder *builder) {
   ir::type *src_ty = input->get_type();
   if (src_ty->is_block_ty())

python/src/triton.cc

@@ -129,6 +129,7 @@ void init_triton_frontend(py::module &&m) {
   typedef ir::value *(*broadcast_to_ty)(ir::value *, ir::type::block_shapes_t, ir::builder *);
   m.def("broadcast", (broadcast_ty)(&ir::dispatch::broadcast), ret::reference);
   m.def("broadcast_to", (broadcast_to_ty)(&ir::dispatch::broadcast), ret::reference);
+  m.def("bitcast", &ir::dispatch::bitcast, ret::reference);
   m.def("cast", &ir::dispatch::cast, ret::reference);
   // memory
   m.def("load", &ir::dispatch::load, ret::reference);

python/test/test_language.py

@@ -263,6 +263,38 @@ def test_atomic_add(dtype_x, device='cuda'):
     triton.testing.assert_allclose(x_ref, last_sum)
 
 
+# ---------------
+# test cast
+# ---------------
+@pytest.mark.parametrize("dtype_x, dtype_z, bitcast", [
+    (dtype_x, dtype_z, False) for dtype_x in dtypes \
+                       for dtype_z in dtypes
+] + [
+    ('float32', 'int32', True)
+])
+def test_cast(dtype_x, dtype_z, bitcast, device='cuda'):
+    x = torch.tensor([43.5], dtype=cvt[dtype_x], device=device)
+
+    # triton kernel
+    @triton.jit
+    def kernel(X, Z, **meta):
+        x = tl.load(X)
+        z = x.to(Z.dtype.element_ty, bitcast=meta['BITCAST'])
+        tl.store(Z, z)
+
+    # triton result
+    z_tri = torch.empty((1, ), dtype=cvt[dtype_z], device=device)
+    kernel[(1, )](x, z_tri, BITCAST=bitcast)
+    # torch result
+    if bitcast:
+        import numpy as np
+        z_ref = x.detach().cpu().numpy().view(getattr(np, dtype_z))
+        z_ref = torch.from_numpy(z_ref).to(device)
+    else:
+        z_ref = x.to(z_tri.dtype)
+    assert z_tri == z_ref
+
+
 # ---------------
 # test load
 # ---------------

python/triton/language.py

@@ -76,7 +76,7 @@ class pointer_dtype:
         self.element_ty = element_ty
 
     def handle(self, builder):
-        return ir.type.make_ptr(self.element_ty, 1)
+        return ir.type.make_ptr(self.element_ty.handle(builder), 1)
 
 
 int1 = dtype(ir.type.get_int1)
@@ -249,8 +249,11 @@ class block:
         return ret
 
     @builtin
-    def to(self, dtype, builder=None):
-        return frontend.cast(self, dtype.handle(builder), builder)
+    def to(self, dtype, bitcast=False, builder=None):
+        dtype = dtype.handle(builder)
+        if bitcast:
+            return frontend.bitcast(self, dtype, builder)
+        return frontend.cast(self, dtype, builder)
 
 
 # -----------------------