[llvm] [RISCV] Add profitability checks to SelectAddrRegRegScale. (PR #150135)

[Craig Topper via llvm-commits]

================
@@ -3032,6 +3032,63 @@ bool RISCVDAGToDAGISel::SelectAddrRegImmLsb00000(SDValue Addr, SDValue &Base,
   return true;
 }
 
+/// Return true if this a load/store that we have a RegRegScale instruction for.
+static bool isRegRegScaleLoadOrStore(SDNode *User, SDValue Add,
+                                     const RISCVSubtarget &Subtarget) {
+  if (User->getOpcode() != ISD::LOAD && User->getOpcode() != ISD::STORE)
+    return false;
+  EVT VT = cast<MemSDNode>(User)->getMemoryVT();
+  if (!(VT.isScalarInteger() &&
+        (Subtarget.hasVendorXTHeadMemIdx() || Subtarget.hasVendorXqcisls())) &&
+      !((VT == MVT::f32 || VT == MVT::f64) &&
+        Subtarget.hasVendorXTHeadFMemIdx()))
+    return false;
+  // Don't allow stores of the value. It must be used as the address.
+  if (User->getOpcode() == ISD::STORE &&
+      cast<StoreSDNode>(User)->getValue() == Add)
+    return false;
+
+  return true;
+}
+
+/// Is it profitable to fold this Add into RegRegScale load/store. If \p
+/// Shift is non-null, then we have matched a shl+add. We allow reassociating
+/// (add (add (shl A C2) B) C1) -> (add (add B C1) (shl A C2)) if there is a
+/// single addi and we don't have a SHXADD instruction we coudl use.
----------------
topperc wrote:

```suggestion
/// single addi and we don't have a SHXADD instruction we could use.
```

https://github.com/llvm/llvm-project/pull/150135