[PATCH] D147597: [InstCombine] Fold icmp(bin(X, Y) | LHS, RHS) --> icmp(bin(X, Y)) iff LHS > RHS s>= 0

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:1959
+  // icmp(bin(X, Y) | LHS, C) --> icmp(bin(X, Y)) iff LHS > C s>= 0
+  if (match(Or, m_c_Or(m_BinOp(BO), m_APInt(LHS)))) {
+    if (LHS->isStrictlyPositive() && C.isNonNegative() && LHS->sgt(C)) {
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I think the BinOp aspect of the transform is meaningless:
https://alive2.llvm.org/ce/z/cbWvv7

Also you're alive2 links still don't match the logic (you are only do `C == 0`).
You can create the constraints you need with `@llvm.assume(i1)`
I tried to implement here: https://alive2.llvm.org/ce/z/rmBJXx
but it doesn't verify.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147597/new/

https://reviews.llvm.org/D147597