[llvm] [RISCV] Match prefetch address with offset (PR #66072)

[Craig Topper via llvm-commits]

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@@ -2443,6 +2449,78 @@ bool RISCVDAGToDAGISel::SelectAddrRegImm(SDValue Addr, SDValue &Base,
   return true;
 }
 
+/// Similar to SelectAddrRegImm, except that the least significant 5 bits of
+/// Offset shoule be all zeros.
+bool RISCVDAGToDAGISel::SelectAddrRegImmLsb00000(SDValue Addr, SDValue &Base,
+                                                 SDValue &Offset) {
+  if (SelectAddrFrameIndex(Addr, Base, Offset))
+    return true;
+
+  SDLoc DL(Addr);
+  MVT VT = Addr.getSimpleValueType();
+
+  if (Addr.getOpcode() == RISCVISD::ADD_LO) {
+    Base = Addr;
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topperc wrote:

This is the default behavior. Why do we need this `if` at all?

https://github.com/llvm/llvm-project/pull/66072