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ff0b826927
Summary: MemoryPhis may be needed following a Def insertion inthe IDF of all the new accesses added (phis + potentially a def). Ensure this also occurs when only the new MemoryPhis are the defining accesses. Note: The need for computing IDF here is because of new Phis added with edges incoming from unreachable code, Phis that had previously been simplified. The preferred solution is to not reintroduce such Phis. This patch is the needed fix while working on the preferred solution. Reviewers: george.burgess.iv Subscribers: Prazek, sanjoy.google, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D67927 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372673 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))
//===---------------------------------------------------------------------===//