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e8187e0294
introduced. Specifically, there are cost reductions for all constant-operand icmp instructions against an alloca, regardless of whether the alloca will in fact be elligible for SROA. That means we don't want to abort the icmp reduction computation when we abort the SROA reduction computation. That in turn frees us from the need to keep a separate worklist and defer the ICmp calculations. Use this new-found freedom and some judicious function boundaries to factor the innards of computing the cost factor of any given instruction out of the loop over the instructions and into static helper functions. This greatly simplifies the code, and hopefully makes it more clear what is happening here. Reviewed by Eric Christopher. There is some concern that we'd like to ensure this doesn't get out of hand, and I plan to benchmark the effects of this change over the next few days along with some further fixes to the inline cost. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152368 91177308-0d34-0410-b5e6-96231b3b80d8
Analysis Opportunities:
//===---------------------------------------------------------------------===//
In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:
{1,+,3,+,2}<loop>
Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as
(-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))
In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.
//===---------------------------------------------------------------------===//
In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,
ScalarEvolution is forming this expression:
((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))
This could be folded to
(-1 * (trunc i64 undef to i32))
//===---------------------------------------------------------------------===//