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7362ac7f8c
constants in C++11 mode. I have no idea why it required such particular circumstances to get here, the code seems clearly to rely upon unchecked assumptions. Specifically, when we decide to form an index into a struct type, we may have gone through (at least one) zero-length array indexing round, which would have left the offset un-adjusted, and thus not necessarily valid for use when indexing the struct type. This is just an canonicalization step, so the correct thing is to refuse to canonicalize nonsensical GEPs of this form. Implemented, and test case added. Fixes PR12642. Pair debugged and coded with Richard Smith. =] I credit him with most of the debugging, and preventing me from writing the wrong code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155466 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))
//===---------------------------------------------------------------------===//