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6231d5be41
spotted by inspection, and I've crafted no test case that triggers it on my machine, but some of the windows builders are hitting what looks like memory corruption, so *something* is amiss here. This patch takes a more generalized approach to eliminating double-visits. Imagine code such as: %x = ... %y = add %x, 1 %z = add %x, %y You can imagine that if we simplify %x, we would add %y and %z to the list. If the use-chain order happens to cause us to add them in reverse order, we could pull %y off first, and simplify it, adding %z to the list. We now have %z on the list twice, and will reference it after it is deleted. Currently, all my test cases happen to not trigger this, likely due to the use-chain ordering, but there seems no guarantee that such a situation could not occur, so we should handle it correctly. Again, if anyone knows how to craft a testcase that actually triggers this, please let me know. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153397 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))
//===---------------------------------------------------------------------===//