[LANG] Added support for constexpr (#361)

python/tutorials/01-vector-add.py

@@ -12,6 +12,7 @@ In this tutorial, you will write a simple vector addition using Triton and learn
 # Compute Kernel
 # --------------------------
 
+from triton.language.core import constexpr
 import torch
 import triton
 import triton.language as tl
@@ -23,9 +24,9 @@ def add_kernel(
     y_ptr,  # *Pointer* to second input vector
     output_ptr,  # *Pointer* to output vector
     n_elements,  # Size of the vector
-    **meta,  # Optional meta-parameters for the kernel
+    BLOCK_SIZE: tl.constexpr,  # Number of elements each program should process
+                 # NOTE: `constexpr` so it can be used as a shape value
 ):
-    BLOCK_SIZE = meta['BLOCK_SIZE']  # How many inputs each program should process
     # There are multiple 'program's processing different data. We identify which program
     # we are here
     pid = tl.program_id(axis=0)  # We use a 1D launch grid so axis is 0
@@ -37,8 +38,8 @@ def add_kernel(
     offsets = block_start + tl.arange(0, BLOCK_SIZE)
     # Create a mask to guard memory operations against out-of-bounds accesses
     mask = offsets < n_elements
-    # Load x and y from DRAM, masking out any extar elements in case the input is not a
-    # multiple of the block size
+    # Load x and y from DRAM, masking out any extra elements in case 
+    # the input is not a multiple of the block size
     x = tl.load(x_ptr + offsets, mask=mask)
     y = tl.load(y_ptr + offsets, mask=mask)
     output = x + y