[AVR] Fix a bug in AsmPrinter when printing memory operands.

[benshi001]

This patch fixes the bug https://github.com/llvm/llvm-project/issues/58874

[aykevl]

LGTM

llvm/lib/Target/AVR/AVRAsmPrinter.cpp

bool AVRAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
   assert(MO.isReg() && "Unexpected inline asm memory operand");
 
   // TODO: We should be able to look up the alternative name for
   // the register if it's given.
   // TableGen doesn't expose a way of getting retrieving names
   // for registers.
   if (MI->getOperand(OpNum).getReg() == AVR::R31R30) {
     O << "Z";
-  } else {
-    assert(MI->getOperand(OpNum).getReg() == AVR::R29R28 &&
-           "Wrong register class for memory operand.");
+  } else if (MI->getOperand(OpNum).getReg() == AVR::R29R28) {
     O << "Y";
+  } else if (MI->getOperand(OpNum).getReg() == AVR::R27R26) {
+    O << "X";
+  } else {
+    assert(false && "Wrong register class for memory operand.");
   }
 
   // If NumOpRegs == 2, then we assume it is product of a FrameIndex expansion
   // and the second operand is an Imm.
   unsigned OpFlags = MI->getOperand(OpNum - 1).getImm();
   unsigned NumOpRegs = InlineAsm::getNumOperandRegisters(OpFlags);
 
   if (NumOpRegs == 2) {
+    assert(MI->getOperand(OpNum).getReg() != AVR::R27R26 &&
+           "Base register X can not have offset/displacement.");
     O << '+' << MI->getOperand(OpNum + 1).getImm();
   }
 
   return false;
 }
 
 void AVRAsmPrinter::emitInstruction(const MachineInstr *MI) {
   // FIXME: Enable feature predicate checks once all the test pass.

llvm/test/CodeGen/AVR/inline-asm/loadstore.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=avr | FileCheck %s
+
+define i8 @loadx(i8* %0) {
+; CHECK-LABEL: loadx:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    mov r26, r24
+; CHECK-NEXT:    mov r27, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    ld r24, X
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    ret
+  %2 = tail call i8 asm sideeffect "ld $0, ${1:a}", "=r,x"(i8* %0)
+  ret i8 %2
+}
+
+define i8 @loady(i8* %0) {
+; CHECK-LABEL: loady:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    push r28
+; CHECK-NEXT:    push r29
+; CHECK-NEXT:    mov r28, r24
+; CHECK-NEXT:    mov r29, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    ld r24, Y
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    pop r29
+; CHECK-NEXT:    pop r28
+; CHECK-NEXT:    ret
+  %2 = tail call i8 asm sideeffect "ld $0, ${1:a}", "=r,y"(i8* %0)
+  ret i8 %2
+}
+
+define i8 @loadz(i8* %0) {
+; CHECK-LABEL: loadz:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    mov r30, r24
+; CHECK-NEXT:    mov r31, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    ld r24, Z
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    ret
+  %2 = tail call i8 asm sideeffect "ld $0, ${1:a}", "=r,z"(i8* %0)
+  ret i8 %2
+}
+
+define void @storex(i8* %0, i8 %1) {
+; CHECK-LABEL: storex:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    mov r26, r24
+; CHECK-NEXT:    mov r27, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    st X, r22
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    ret
+  tail call void asm sideeffect "st ${0:a}, $1", "x,r"(i8* %0, i8 %1)
+  ret void
+}
+
+define void @storey(i8* %0, i8 %1) {
+; CHECK-LABEL: storey:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    push r28
+; CHECK-NEXT:    push r29
+; CHECK-NEXT:    mov r28, r24
+; CHECK-NEXT:    mov r29, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    st Y, r22
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    pop r29
+; CHECK-NEXT:    pop r28
+; CHECK-NEXT:    ret
+  tail call void asm sideeffect "st ${0:a}, $1", "y,r"(i8* %0, i8 %1)
+  ret void
+}
+
+define void @storez(i8* %0, i8 %1) {
+; CHECK-LABEL: storez:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    mov r30, r24
+; CHECK-NEXT:    mov r31, r25
+; CHECK-NEXT:    ;APP
+; CHECK-NEXT:    st Z, r22
+; CHECK-NEXT:    ;NO_APP
+; CHECK-NEXT:    ret
+  tail call void asm sideeffect "st ${0:a}, $1", "z,r"(i8* %0, i8 %1)
+  ret void
+}