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eb9033d963
This teaches the min/max idiom detector in ValueTracking to see through casts such as SExt/ZExt/Trunc. SCEV can already do this, so we're bringing non-SCEV analyses up to the same level. The returned LHS/RHS will not match the type of the original SelectInst any more, so a CastOp is returned too to inform the caller how to convert to the SelectInst's type. No in-tree users yet; this will be used by InstCombine in a followup. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237452 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))
//===---------------------------------------------------------------------===//