After replacing a loop phi with the preheader value, it's usually
possible to simplify some of the using instructions, so do that as
part of replaceLoopPHINodesWithPreheaderValues().
Doing this as part of IndVars is valuable, because it may make GEPs
in the loop have constant offsets and allow the following SROA run
to succeed (as demonstrated in the PhaseOrdering test).
Differential Revision: https://reviews.llvm.org/D129293
Currently we only call replaceLoopPHINodesWithPreheaderValues() if
optimizeLoopExits() replaces the exit with an unconditional exit.
However, it is very common that this already happens as part of
eliminateIVComparison(), in which case we're leaving behind the
dead header phi.
Tweak the early bailout for already-constant exits to also call
replaceLoopPHINodesWithPreheaderValues().
Differential Revision: https://reviews.llvm.org/D129214
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Logic in `getInsertPointForUses` doesn't account for a corner case when `Def`
only comes to a Phi user from unreachable blocks. In this case, the incoming
value may be arbitrary (and not even available in the input block) and break
the loop-related invariants that are asserted below.
In fact, if we encounter this situation, no IR modification is needed. This
Phi will be simplified away with nearest cleanup.
Differential Revision: https://reviews.llvm.org/D58045
Reviewed By: spatel
llvm-svn: 353816
