[PATCH] D65262: [SCEV] simplify more icmps with pred sle/ule to pred slt/ult

[ChenZheng via Phabricator via llvm-commits]

shchenz created this revision.
shchenz added reviewers: nikic, sanjoy, hfinkel, reames, jsji.
Herald added subscribers: llvm-commits, wuzish, javed.absar, MaskRay, hiraditya, nemanjai.
Herald added a project: LLVM.



  define void @sle(i8* %p, i32 %a, i32 %b) {
  ...
  for.body: 
  %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
  %inc = add nsw i32 %i.04, 1
  %cmp = icmp sle i32 %inc, %b
  br i1 %cmp, label %for.body, label %for.end
  ...
  }

SCEV for `add` is `{%a, +, 1}`, SCEV for `icmp` LHS is `{(%a + 1) <nsw>, + , 1}`. Currently, the range for LHS is full-set.

In patch https://reviews.llvm.org/D64869, the range for LHS is corrected to `[INT32_MIN+1, INT32_MIN)`.

This patch is based on the fixed range in https://reviews.llvm.org/D64869 to get `backedge-taken` for more loops. We can convert more `sle/ule` to `slt/ult`.


https://reviews.llvm.org/D65262

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/trip-count15.ll
  llvm/test/CodeGen/PowerPC/ctrloop-le.ll

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