[AVR] Fix incorrect selection of post indexed addresses

llvm/lib/Target/AVR/AVRISelLowering.cpp

@@ -1114,8 +1114,22 @@ bool AVRTargetLowering::getPostIndexedAddressParts(SDNode *N, SDNode *Op,
       if (AVR::isProgramMemoryAccess(LD))
         return false;
 
+    SDValue Ptr;
+    if (LoadSDNode *LD = dyn_cast<LoadSDNode>(N)) {
+      Ptr = LD->getBasePtr();
+    } else if (StoreSDNode *ST = dyn_cast<StoreSDNode>(N)) {
+      Ptr = ST->getBasePtr();
+    } else
+      return false;
+
     Base = Op->getOperand(0);
     Offset = DAG.getConstant(RHSC, DL, MVT::i8);
+
+    // Post-indexing updates the base, so it's not a valid transform
+    // if that's not the same as the load's pointer.
+    if (Ptr != Base)
+      return false;
+
     AM = ISD::POST_INC;
 
     return true;

llvm/test/CodeGen/AVR/issue-145040.ll

@@ -0,0 +1,23 @@
+; RUN: llc < %s -O=2 -mtriple=avr-none --mcpu=avr128db28 -verify-machineinstrs | FileCheck %s
+
+declare dso_local void @nil(i16 noundef) local_unnamed_addr addrspace(1) #1
+!3 = !{!4, !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}
+
+define void @complex_sbi() {
+; CHECK: sbi 1, 7
+entry:
+  br label %while.cond
+while.cond:                                       ; preds = %while.cond, %entry
+  %s.0 = phi i16 [ 0, %entry ], [ %inc, %while.cond ]
+  %inc = add nuw nsw i16 %s.0, 1
+  %0 = load volatile i8, ptr inttoptr (i16 1 to ptr), align 1, !tbaa !3
+  %or = or i8 %0, -128
+  store volatile i8 %or, ptr inttoptr (i16 1 to ptr), align 1, !tbaa !3
+  %and = and i16 %inc, 15
+  %add = add nuw nsw i16 %and, 1
+  tail call addrspace(1) void @nil(i16 noundef %add) #2
+  br label %while.cond
+}
+