[OpaquePtr][LoopAccessAnalysis] Support opaque pointers

[aeubanks]

Summary

Previously we relied on the pointee type to determine what type we need
to do runtime pointer access checks.

With opaque pointers, we can access a pointer with more than one type,
so now we keep track of all the types we're accessing a pointer's
memory with.

Also some other minor getPointerElementType() removals.

[nikic]

Looks correct to me, but it would be good to check that the result is actually correct. Maybe add an opaque pointers version of an existing test? depend_diff_types.ll looks like a good candidate, because it deals with bitcasted accesses.

[aeubanks]

fix all of LAA, needed to get the test working with opaque pointers

[nikic]

Looks reasonable to me. I think ideally this code would be working based on the largest store size used in any access or something like that, but I think your current implementation matches what this code currently does for non-opaque pointers in spirit.

llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types_opaque_ptr.ll

38

These ptr-to-ptr bitcasts should be dropped, to make sure that we actually test the case where the same Value * is accessed with different types. Right now, this artificially creates separate pointer values.

[fhahn]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

822

I think we need at least test cases where there are actually more than on AccessTy. This seems not be be covered by the existing tests at the moment

[aeubanks]

update test to not have bitcasts
required updating LoopAccessInfo::analyzeLoop() to take AccessTy into account alongside the pointer value

[fhahn]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

822

Did you check if there's a test case with multiple access types that covers this code? It seems like this is still missing. One way to test this would be to have a loop-versioning test. IIUC multiple checks need to be generated with the correct access types now.

[aeubanks]

llvm/lib/Analysis/LoopAccessAnalysis.cpp

822

Oh sorry I got this part confused with the part above. I'm not super familiar with this so any help with constructing a test case would be appreciated, but I'll try to come up with one.