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David Greene
53a00b6727
Re-apply 9fdfb045ae8b/r365676 with fixes for PPC and Hexagon. This involved moving defaults from TargetTransformInfoImplBase to MCSubtargetInfo. Rework the TTI cache and software prefetching APIs to prepare for the introduction of a general system model. Changes include: - Marking existing interfaces const and/or override as appropriate - Adding comments - Adding BasicTTIImpl interfaces that delegate to a subtarget implementation - Moving the default TargetTransformInfoImplBase implementation to a default MCSubtarget implementation Only a handful of targets use these interfaces currently: AArch64, Hexagon, PPC and SystemZ. AArch64 already has a custom subtarget implementation, so its custom TTI implementation is migrated to use the new facilities in BasicTTIImpl to invoke its custom subtarget implementation. The custom TTI implementations continue to exist for the other targets with this change. They are not moved over to subtarget-based implementations. The end goal is to have the default subtarget implementation defer to the system model defined by the target. With this change, the default MCSubtargetInfo implementation essentially returns the defaults TargetTransformInfoImplBase used to return. Existing users of TTI defaults will hit the defaults now in MCSubtargetInfo. Targets that define their own custom TTI implementations won't use the BasicTTIImpl implementations that route to the subtarget. Once system models are in place for the targets that use these interfaces, their custom TTI implementations can be removed. Differential Revision: https://reviews.llvm.org/D63614 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374205 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))
//===---------------------------------------------------------------------===//