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04fe990190
BasicAA contains knowledge of certain intrinsics, such as memcpy and memset, and uses that information to form more-accurate answers to CallSite vs. Loc ModRef queries. Unfortunately, it did not use this information when answering CallSite vs. CallSite queries. Generically, when an intrinsic takes one or more pointers and the intrinsic is marked only to read/write from its arguments, the offset/size is unknown. As a result, the generic code that answers CallSite vs. CallSite (and CallSite vs. Loc) queries in AA uses UnknownSize when forming Locs from an intrinsic's arguments. While BasicAA's CallSite vs. Loc override could use more-accurate size information for some intrinsics, it did not do the same for CallSite vs. CallSite queries. This change refactors the intrinsic-specific logic in BasicAA into a generic AA query function: getArgLocation, which is overridden by BasicAA to supply the intrinsic-specific knowledge, and used by AA's generic implementation. This allows the intrinsic-specific knowledge to be used by both CallSite vs. Loc and CallSite vs. CallSite queries, and simplifies the BasicAA implementation. Currently, only one function, Mac's memset_pattern16, is handled by BasicAA (all the rest are intrinsics). As a side-effect of this refactoring, BasicAA's getModRefBehavior override now also returns OnlyAccessesArgumentPointees for this function (which is an improvement). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212572 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))
//===---------------------------------------------------------------------===//