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Hello,Ok. Thanks for the patch.
The patch repairs a problem when we attempt to substitute an insn like (... (cmp (mem (reg:DI ax)) (reg:SI ax))) (note different modes) through (set (reg:DI ax) (reg:DI dx)), which leaves the (reg:SI ax) part of the comparison intact, causing an ICE later on when we notice that the dependency on ax is still present. As this is quite rare, we can simply forbid substitution in such circumstances, much like substitution of multiple hard reg references is forbidden now.
En passant, the patch simplifes the code a little, as we never try to substitute anything but registers.
Bootstrapped and regtested on x86_64-linux with sel-sched enabled at -O2, OK? (I'll add the testcase from Bugzilla when committing)
2011-09-07 Alexander Monakov<amonakov@ispras.ru>
PR rtl-optimization/50205 * sel-sched.c (count_occurrences_1): Simplify on the assumption that p->x is a register. Forbid substitution when the same register is found in a different mode. (count_occurrences_equiv): Assert that 'what' is a register.
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