Fix recent bug in canonicalize_comparison (PR87026)

Fix recent bug in canonicalize_comparison (PR87026)

The new code testing which way a comparison is best expressed creates
a pseudoregister (by hand) and creates some insns with that.  Such
insns will no longer recog() when pseudo-registers are no longer
aloowed (after reload).  But we have an ifcvt pass after reload (ce3).

This patch simply returns if we cannot create pseudos.

	PR rtl-optimization/87026
	* expmed.c (canonicalize_comparison): If we can no longer create
	pseudoregisters, don't.

From-SVN: r263810