Examples of different width ops

diff --git a/openpower/sv/svp_rewrite/svp64/discussion.mdwn b/openpower/sv/svp_rewrite/svp64/discussion.mdwn
index 3b0830295baf62ba2008e52ed45c85535cff1d8c..0bb8fc2e579b049ab2bddc4d75baefc7ab2ee940 100644 (file)
--- a/openpower/sv/svp_rewrite/svp64/discussion.mdwn
+++ b/openpower/sv/svp_rewrite/svp64/discussion.mdwn
@@ -81,6 +81,14 @@ Note:
   be proven using the lower will lead to the same result
 * saturation is done on the result at the **dest** elwidth
 
+Some examples on different operation widths:
+
+    u16 / u16 = u8
+    256 / 2 = 128 # if we used the smaller width, we'd get 0. Wrong
+
+    u8 * u8 = u16
+    255 * 2 = 510 # if we used the smaller width, we'd get 254. Wrong
+
 # Notes about rounding, clamp and saturate
 
 One of the issues with vector ops is that in integer DSP ops for example in Audio the operation must clamp or saturate rather than overflow or ignore the upper bits and become a modulo operation.  This for Audio is extremely important, also to provide an indicator as to whether saturation occurred.  see  [[av_opcodes]].