[Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #8 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-11 09:46:06 UTC ---
Backporting r186159 and its followup fix r186164 to 4.7.1 was easy and fixed
the test case there too (untested beyond this test case).  Backporting those
revisions to 4.6.3 required more elbow grease but didn't fix the test case
there.

I'm going to test the 4.7 backport properly now, in case a smaller more direct
fix doesn't emerge soon.