[llvm] [ValueTracking] Handle non-canonical operand order in `isImpliedCondICmps` (PR #85575)

[Nikita Popov via llvm-commits]

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@@ -8532,39 +8518,41 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
   CmpInst::Predicate LPred =
       LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
 
+  // We can have non-canonical operands, so try to normalize any common operand
+  // to L0/R0.
+  if (L0 == R1) {
+    std::swap(R0, R1);
+    RPred = ICmpInst::getSwappedPredicate(RPred);
+  }
+  if (R0 == L1) {
+    std::swap(L0, L1);
+    LPred = ICmpInst::getSwappedPredicate(LPred);
+  }
+  if (L1 == R1) {
+    // If we have L0 == R0 and L1 == R1, then make L1/R1 the constants.
+    if (L0 != R0 || match(L0, m_ImmConstant())) {
+      std::swap(L0, L1);
+      LPred = ICmpInst::getSwappedPredicate(LPred);
+      std::swap(R0, R1);
+      RPred = ICmpInst::getSwappedPredicate(RPred);
+    }
+  }
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nikic wrote:

nit: Add a newline here?

https://github.com/llvm/llvm-project/pull/85575