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computeKnownBits() already works for integer vectors, so allow vector types when calling that from InstCombine. I don't think the change to use m_APInt in computeKnownBits is strictly necessary because we do check for ConstantVector later, but it's more efficient to handle the splat case without needing to loop on vector elements. This should work with InstSimplify, but doesn't yet, so I made that a FIXME comment on the test for PR24942: https://llvm.org/bugs/show_bug.cgi?id=24942 Differential Revision: https://reviews.llvm.org/D24677 llvm-svn: 281777
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))
//===---------------------------------------------------------------------===//