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a60f524c80
IndVarSimplify assumes scAddRecExpr to be expanded in literal form instead of canonical form by calling disableCanonicalMode after it creates SCEVExpander. When CanonicalMode is disabled, SCEVExpander::expand should always return PHI node for scAddRecExpr. r259736 broke the assumption. The fix is to let SCEVExpander::expand skip the reuse Value logic if CanonicalMode is false. In addition, Besides IndVarSimplify, LSR pass also calls disableCanonicalMode before doing rewrite. We can remove the original check of LSRMode in reuse Value logic and use CanonicalMode instead. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260174 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))
//===---------------------------------------------------------------------===//