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This patch exports 'compute_antinout_edge' and 'compute_earliest' as global scope
which is going to be used in VSETVL PASS of RISC-V backend.
The demand fusion is the fusion of VSETVL information to emit VSETVL which dominate and pre-config for most
of the RVV instructions in order to elide redundant VSETVLs.
For exmaple:
for
for
for
if (cond}
VSETVL demand 1: SEW/LMUL = 16 and TU policy
else
VSETVL demand 2: SEW = 32
VSETVL pass should be able to fuse demand 1 and demand 2 into new demand: SEW = 32, LMUL = M2, TU policy.
Then emit such VSETVL at the outmost of the for loop to get the most optimal codegen and run-time execution.
Currenty the VSETVL PASS Phase 3 (demand fusion) is really messy and un-reliable as well as un-maintainable.
And, I recently read dragon book and morgan's book again, I found there "earliest" can allow us to do the
demand fusion in a very reliable and optimal way.
So, this patch exports these 2 functions which are very helpful for VSETVL pass.
gcc/ChangeLog:
* lcm.cc (compute_antinout_edge): Export as global use.
(compute_earliest): Ditto.
(compute_rev_insert_delete): Ditto.
* lcm.h (compute_antinout_edge): Ditto.
(compute_earliest): Ditto.
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