Unused loop invariant loads were not sunk from the preheader to the exit
block, increasing live range.
This commit moves the sinkUnusedInvariant logic from indvarsimplify to
LICM also adds functionality to sink unused load that's not
clobbered by the loop body.
The current isHighCostExpansion cost model for addrecs computes the cost
for some kind of polynomial expansion that does not appear to have any
relation to addrec expansion whatsoever.
A literal expansion of an affine addrec is a phi and add (plus the
expansion of start and step). For a non-affine addrec, we get another
phi+add for each additional addrec nested in the step recurrence.
This partially `fixes` https://github.com/llvm/llvm-project/issues/53205
(the runtime unroll test case in this PR).
When bailing out in rewriteLoopExitValues() you could be left with PHI
nodes in the DeadInsts vector. Those would be not handled by the use of
RecursivelyDeleteTriviallyDeadInstructions() in IndVarSimplify. This
resulted in the IndVarSimplify pass returning an incorrect modified
status. This was caught by the expensive check introduced in D86589.
This patches changes IndVarSimplify so that it deletes those PHI nodes,
using RecursivelyDeleteDeadPHINode().
This fixes PR47486.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D91153
