The following patch is a fix for PR rtl-optimization/17853 suitable
for the gcc-3_4-branch. On mainline, the appropriate long term fix was
to provide the infrastructure for constant folding vector comparisons.
For the release branch, however, its probably better/safer to go
with Stuart Hastings' preference of just disabling the problematic
transformations.
It's interesting to observe that the recent clean-up of the RTL
optimizers on mainline means that this problematic transformation may
now be disabled at a single point. Unfortunately, for gcc 3.4.x, the
simplification of relational expressions is duplicated in (at least)
four places, all of which need to be touched by this patch.
The following patch has been tested against the gcc-3_4-branch on
i686-pc-linux-gnu with a full "make bootstrap", all default languages,
and regression tested with a top-level "make -k check" with no new
failures. The testcase below is identical to the one on mainline.
Ok for the gcc-3_4-branch?