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05e15f8897
phi translation of complex expressions like &A[i+1]. This has the following benefits: 1. The phi translation logic is all contained in its own class with a strong interface and verification that it is self consistent. 2. The logic is more correct than before. Previously, if intermediate expressions got PHI translated, we'd miss the update and scan for the wrong pointers in predecessor blocks. @phi_trans2 is a testcase for this. 3. We have a lot less code in memdep. We can handle phi translation across blocks of things like @phi_trans3, which is pretty insane :). This patch should fix the miscompiles of 255.vortex, and I tested it with a bootstrap of llvm-gcc, llvm-test and dejagnu of course. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90926 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.
//===---------------------------------------------------------------------===//