intel/executor: Add small example with bfloat

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Rohan Garg <rohan.garg@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33664>

src/intel/executor/examples/bfloat.lua

@@ -0,0 +1,50 @@
+local r = execute {
+  src=[[
+    @id      g3
+
+    mov(8)   g4<1>F    g3<1>UD                       {A@1};
+    mov(8)   g5<1>F    g4.2<0,1,0>F                  {A@1};
+
+    // Moving from F to BF (packed) doesn't work, but that's not much
+    // of a problem because BFloat16 is a cropped version of Float32.
+    //
+    // So instead of
+    //
+    //     mov(8)   g10<1>BF  g4<1>F
+    //
+    // use MOV with UW and appropriate offset.
+    mov(8)   g10<1>UW  g4.1<2>UW                     {A@1};
+
+    mad(8)   g11<1>BF  g4<1>F    g10<1>BF  g5<1>F    {A@1};
+    add(8)   g12<1>BF  g11<1>BF  g4<1>F              {A@1};
+
+    // For similar reason as above, instead of
+    //
+    //     mov(8)   g20<1>F   g12<1>BF
+    //
+    // use a SHL unpacking into UD.
+    shl(8)   g20<1>UD  g12<1>UW  16UW                {A@1};
+
+    mov(8)   g21<1>UD  g20<1>F                       {A@1};
+    @write   g3        g21
+
+    @eot
+  ]]
+}
+
+expected = {[0] = 0, 4, 8, 12, 16, 20, 24, 28}
+
+print("result")
+dump(r, 8)
+
+print("expected")
+dump(expected, 8)
+
+for i=0,7 do
+  if r[i] ~= expected[i] then
+    print("FAIL")
+    return
+  end
+end
+
+print("OK")