gcc/ChangeLog:
PR debug/42631
* web.c (union_defs): Add used argument, to combine uses of
uninitialized regs.
(entry_register): Adjust type and tests of used argument.
(web_main): Widen used for new use.  Pass it to union_defs.
* df.h (union_defs): Adjust prototype.
gcc/testsuite/ChangeLog:
PR debug/42631
* gcc.dg/pr42631.c: New.

From-SVN: r155765