Add RV64 constraint to SRLIW (#69416)

Fixes #69408

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -1013,12 +1013,12 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
     unsigned TrailingOnes = llvm::countr_one(Mask);
     if (ShAmt >= TrailingOnes)
       break;
-    // If the mask has 32 trailing ones, use SRLIW.
+    // If the mask has 32 trailing ones, use SRLI on RV32 or SRLIW on RV64.
     if (TrailingOnes == 32) {
-      SDNode *SRLIW =
-          CurDAG->getMachineNode(RISCV::SRLIW, DL, VT, N0->getOperand(0),
-                                 CurDAG->getTargetConstant(ShAmt, DL, VT));
-      ReplaceNode(Node, SRLIW);
+      SDNode *SRLI = CurDAG->getMachineNode(
+          Subtarget->is64Bit() ? RISCV::SRLIW : RISCV::SRLI, DL, VT,
+          N0->getOperand(0), CurDAG->getTargetConstant(ShAmt, DL, VT));
+      ReplaceNode(Node, SRLI);
       return;
     }
 

llvm/test/CodeGen/RISCV/aext.ll

@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32I %s
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64I %s
+
+define i24 @aext(i32 %0) {
+; RV32I-LABEL: aext:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    srli a0, a0, 8
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: aext:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    srliw a0, a0, 8
+; RV64I-NEXT:    ret
+  %2 = and i32 %0, -256
+  %3 = lshr exact i32 %2, 8
+  %4 = trunc i32 %3 to i24
+  ret i24 %4
+}