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017dde1e72
more dense datastructure. We actually only have 3 bits of information and an often-null pointer here. This fits very nicely into a pointer-size value in the DenseMap from Function -> Info. Then we take one more pointer hop to get to a secondary DenseMap from GlobalValue -> ModRefInfo when we actually have precise info for particular globals. This is more code than I would really like to do this packing, but it ended up reasonably cleanly laid out. It should ensure we don't hit scaling limitations with more widespread use of GMR. llvm-svn: 242991
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))
//===---------------------------------------------------------------------===//