Use ValueOffsetPair to enhance value reuse during SCEV expansion.
In D12090, the ExprValueMap was added to reuse existing value during
SCEV expansion. However, const folding and sext/zext distribution can
make the reuse still difficult.
A simplified case is: suppose we know S1 expands to V1 in
ExprValueMap, and
S1 = S2 + C_a
S3 = S2 + C_b
where C_a and C_b are different SCEVConstants. Then we'd like to
expand S3 as V1 - C_a + C_b instead of expanding S2 literally. It is
helpful when S2 is a complex SCEV expr and S2 has no entry in
ExprValueMap, which is usually caused by the fact that S3 is
generated from S1 after const folding.
In order to do that, we represent ExprValueMap as a mapping from SCEV
to ValueOffsetPair. We will save both S1->{V1, 0} and S2->{V1, C_a}
into the ExprValueMap when we create SCEV for V1. When S3 is
expanded, it will first expand S2 to V1 - C_a because of S2->{V1,
C_a} in the map, then expand S3 to V1 - C_a + C_b.
Differential Revision: https://reviews.llvm.org/D21313
This should fix assertion failures when building OpenCV >= 3.1.
PR: 215649
MFC after: 3 days
Note that mandoc does not use anymore sqlite3 but a home made database format
An important improvement has been made as well in makewhatis performance:
Tests on my laptop shows makewhatis on the entire system goes from 26s to 12s
to a non-wildcard address. As documented in ip(4), doing sendmsg(2) with
IP_SENDSRCADDR on a socket that is bound to non-wildcard address is
completely different to using this control message on a wildcard one.
A fix is to add a bool to mark whether we did setsockopt(IP_RECVDSTADDR)
on the socket, and use IP_SENDSRCADDR control message only if we did.
While here, garbage collect absolutely useless udp_recv() function that
establishes some structures on stack to never use them later.
It was used for nitems, but I converted it to __arraycount later, and
is already pulled in by header pollution on FreeBSD as well as NetBSD
ala sys/cdefs.h
unlinking them at the beginning of the testcase
This is a lot more intelligent in cleaning up the semaphores if the testcase
fails before sem_unlink is called.
Contributed back as bin/51872 upstream.
