[llvm] [ValueTracking] Improve `isImpliedCondICmps` to handle binops (PR #69840)

[via llvm-commits]

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@@ -8272,8 +8280,36 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
   // Can we infer anything when the 0-operands match and the 1-operands are
   // constants (not necessarily matching)?
   const APInt *LC, *RC;
-  if (L0 == R0 && match(L1, m_APInt(LC)) && match(R1, m_APInt(RC)))
-    return isImpliedCondCommonOperandWithConstants(LPred, *LC, RPred, *RC);
+  if (match(L1, m_APInt(LC)) && match(R1, m_APInt(RC))) {
+    if (L0 == R0)
+      return isImpliedCondCommonOperandWithConstants(LPred, *LC, RPred, *RC);
+
+    // handle R0 = L0 binop V and R0 = V binop L0
+    Value *R0Op1 = nullptr;
+    if (match(R0, m_c_BinOp(m_Specific(L0), m_Value(R0Op1)))) {
+      ConstantRange LHSRange = ConstantRange::makeExactICmpRegion(LPred, *LC);
+      ConstantRange CR = ConstantRange::makeExactICmpRegion(RPred, *RC);
+      // TODO: use contextual information from SimplifyQuery
+      ConstantRange RHSRange =
+          computeConstantRange(R0Op1, ICmpInst::isSigned(RPred),
+                               /*UseInstrInfo*/ true, /*AC*/ nullptr,
+                               /*CtxI*/ nullptr, /*DT*/ nullptr, Depth);
+      auto *BO = cast<BinaryOperator>(R0);
+      if (BO->getOperand(0) != L0)
+        std::swap(LHSRange, RHSRange);
+      unsigned NoWrapKind = 0;
+      if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(BO)) {
+        if (OBO->hasNoUnsignedWrap())
+          NoWrapKind |= OverflowingBinaryOperator::NoUnsignedWrap;
+        if (OBO->hasNoSignedWrap())
+          NoWrapKind |= OverflowingBinaryOperator::NoSignedWrap;
+      }
+      ConstantRange Range =
+          LHSRange.overflowingBinaryOp(BO->getOpcode(), RHSRange, NoWrapKind);
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goldsteinn wrote:

Still a bit confused about why `LHSRange` is based on the constant range of `LHS` and not of `L0`.

https://github.com/llvm/llvm-project/pull/69840