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------------------------------------------------------------------------ r228525 | bsteinbr | 2015-02-08 09:07:14 -0800 (Sun, 08 Feb 2015) | 14 lines Correctly combine alias.scope metadata by a union instead of intersecting Summary: The alias.scope metadata represents sets of things an instruction might alias with. When generically combining the metadata from two instructions the result must be the union of the original sets, because the new instruction might alias with anything any of the original instructions aliased with. Reviewers: hfinkel Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D7490 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@228561 91177308-0d34-0410-b5e6-96231b3b80d8
Analysis Opportunities:
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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.
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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))
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