[llvm] Retry "[SDAG] (abs (add nsw a, -b)) -> (abds a, b) (#175801)" (PR #186659)

[Simon Pilgrim via llvm-commits]

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@@ -11854,34 +11854,73 @@ SDValue DAGCombiner::foldABSToABD(SDNode *N, const SDLoc &DL) {
   EVT VT = N->getValueType(0);
   SDValue Op0, Op1;
 
-  if (!sd_match(N, m_Abs(m_Sub(m_Value(Op0), m_Value(Op1)))))
+  if (!sd_match(N, m_Abs(m_AnyOf(m_Sub(m_Value(Op0), m_Value(Op1)),
+                                 m_Add(m_Value(Op0), m_Value(Op1))))))
     return SDValue();
 
   SDValue AbsOp0 = N->getOperand(0);
+  bool IsAdd = AbsOp0.getOpcode() == ISD::ADD;
+  // Make sure (neg B) is positive.
+  if (IsAdd) {
+    // Elements of Op1 must be constant and != VT.minSignedValue() (or undef)
+    std::function<bool(ConstantSDNode *)> IsNotMinSignedInt =
+        [VT](ConstantSDNode *C) {
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RKSimon wrote:

(style) this is one of the few times we tend to use auto:
```
auto IsNotMinSignedInt = [VT](ConstantSDNode *C) {
```

https://github.com/llvm/llvm-project/pull/186659