[FRONTEND] Fix the implicit broadcasting rule (#663)

This PR solves the cast issue that appears in some tutorial code.

python/tests/test_cast.py

@@ -0,0 +1,56 @@
+import triton
+import triton.language as tl
+
+
+@triton.jit
+def cast_check():
+    zero_0d = tl.zeros([], dtype=tl.float32)
+    zero_1d = tl.zeros([2], dtype=tl.float32)
+    zero_2d_21 = tl.zeros([2, 1], dtype=tl.float32)
+    zero_2d_22 = tl.zeros([2, 2], dtype=tl.float32)
+
+    # scalar + scalar -> scalar
+    a0 = 0.0 + 0.0
+    # scalar + 0D -> 0D
+    a1 = 0.0 + zero_0d
+    a2 = zero_0d + 0.0
+    # scalar + 1D -> 1D
+    a3 = 0.0 + zero_1d
+    a4 = zero_1d + 0.0
+    # scalar + 2D -> 2D
+    a5 = 0.0 + zero_2d_22
+    a6 = zero_2d_22 + 0.0
+
+    # 0D + 0D -> 0D
+    b1 = zero_0d + zero_0d
+    # 0D + 1D -> 1D
+    b2 = zero_0d + zero_1d
+    b3 = zero_1d + zero_0d
+    # 0D + 2D -> 2D
+    b4 = zero_0d + zero_2d_22
+    b5 = zero_2d_22 + zero_0d
+
+    # 1D + 1D -> 1D
+    c1 = zero_1d + zero_1d
+    # 1D + 2D -> 2D
+    c2 = zero_1d + zero_2d_21
+    c3 = zero_1d + zero_2d_22
+    c4 = zero_2d_21 + zero_1d
+    c5 = zero_2d_22 + zero_1d
+
+    # 2D + 2D -> 2D
+    d1 = zero_2d_21 + zero_2d_21
+    d2 = zero_2d_22 + zero_2d_22
+    d3 = zero_2d_21 + zero_2d_22
+    d4 = zero_2d_22 + zero_2d_21
+
+    return a0, a1, a2, a3, a4, a5, a6, b1, b2, b3, b4, b5, c1, c2, c3, c4, c5, d1, d2, d3, d4
+
+
+def test_cast_check():
+    kernel = triton.compile(cast_check,
+                            signature="",
+                            device=0,
+                            output="ttir")
+    assert (kernel)
+    # TODO: Check types of the results