Decreased performance when compiling with no options...

One of the things that we've done in Whidbey is add some extra IL instructions to improve the debugging experience. This allows you to (for example) set a break on a closing brace.

Because /o- is the default setting, this means that performance if you just compile with “csc” will be slightly degraded in Whidbey. If you've been building without setting /o+ and you care about perf, you will want to change your code to throw /o+ explicitly.

If you're using VS release and debug configurations, this will be set automatically for you.

Comments

• Anonymous
  July 12, 2004
  I get the feeling that's going to usher in a whole raft of unfavourable Java-C# benchmarks :-)
  
  But if this is for debugging, why not just set /o- implicitly if the /debug flag is set, and leave /o+ for release builds?
  
  Jim
• Anonymous
  July 12, 2004
  If you aren't running under the debugger, are there any IL instructions generated that the JITter can't optimize away?
• Anonymous
  July 12, 2004
  Which new IL opcodes are these?
• Anonymous
  July 12, 2004
  Mike: I think they are just nop instructions. So the opcodes aren't new, but the fact that the compiler emits them is.
  
• Anonymous
  July 14, 2004
  I agree with Jum. Why not just set the /o+ option when you set the Release build option?
• Anonymous
  July 14, 2004
  Sorry, meant the /debug flag, and not the Release option under Configuration Manager.
• Anonymous
  July 14, 2004
  Eric Gunnerson blogs about. Apparently, nop instructions are now inserted in BOTH VB.NET and C# to allow breakpoints to be set on End Sub or braces lines. Adding the /o+ compiler option removes these statements, providing better code performance. Someone...
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  December 27, 2004
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  March 18, 2008
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