Minor documentation problem

[Ioannis E. Venetis]

Hello,

I downloaded gcc 4.0.1 and created the manual with 'make dvi'. While 
browsing through it, I noticed the option -ftree-dse, which is mentioned 
in paragraph 3.1 (Options summary) and in paragraph 3.10 (Options That 
Control Optimization) under -O1.

However, this option is not documented in the manual. What does it do?

Thank you,

Ioannis