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efbb95a1be
Reapply r223347, with a fix to not crash on uninserted instructions (or more precisely, instructions in uninserted blocks). bugpoint was able to reduce the test case somewhat, but it is still somewhat large (and relies on setting things up to be simplified during inlining), so I've not included it here. Nevertheless, it is clear what is going on and why. Original commit message: Restrict somewhat the memory-allocation pointer cmp opt from r223093 Based on review comments from Richard Smith, restrict this optimization from applying to globals that might resolve lazily to other dynamically-loaded modules, and also from dynamic allocas (which might be transformed into malloc calls). In short, take extra care that the compared-to pointer is really simultaneously live with the memory allocation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223371 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))
//===---------------------------------------------------------------------===//