https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82090
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |aldyh at gcc dot gnu.org,
| |amacleod at redhat dot com,
| |law at gcc dot gnu.org
--- Comment #3 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
> Jump threading probably gives up because of the asm ().
Actually the problem is the number of instructions in the asm.
The path starting at 3->4 would elide the undefined read but the asm has a ton
of statements and the threadfull* passes fail to even look at the path:
Checking profitability of path (backwards): bb:4 (18 insns) bb:3
Control statement insns: 2
Overall: 16 insns
FAIL: Did not thread around loop and would copy too many statements.
Assuming estimate_num_insns() is correct for the asm inline, we can't depend on
the threader.
Hmmm, I keep thinking we need a path solver/ranger aware uninit pass :).
