Index: llvm/lib/Target/AVR/AVRISelLowering.cpp
===================================================================
--- llvm/lib/Target/AVR/AVRISelLowering.cpp
+++ llvm/lib/Target/AVR/AVRISelLowering.cpp
@@ -2075,37 +2075,20 @@
 
   if (VT == LLT::scalar(8)) {
     Reg = StringSwitch<unsigned>(RegName)
-      .Case("r0", AVR::R0).Case("r1", AVR::R1).Case("r2", AVR::R2)
-      .Case("r3", AVR::R3).Case("r4", AVR::R4).Case("r5", AVR::R5)
-      .Case("r6", AVR::R6).Case("r7", AVR::R7).Case("r8", AVR::R8)
-      .Case("r9", AVR::R9).Case("r10", AVR::R10).Case("r11", AVR::R11)
-      .Case("r12", AVR::R12).Case("r13", AVR::R13).Case("r14", AVR::R14)
-      .Case("r15", AVR::R15).Case("r16", AVR::R16).Case("r17", AVR::R17)
-      .Case("r18", AVR::R18).Case("r19", AVR::R19).Case("r20", AVR::R20)
-      .Case("r21", AVR::R21).Case("r22", AVR::R22).Case("r23", AVR::R23)
-      .Case("r24", AVR::R24).Case("r25", AVR::R25).Case("r26", AVR::R26)
-      .Case("r27", AVR::R27).Case("r28", AVR::R28).Case("r29", AVR::R29)
-      .Case("r30", AVR::R30).Case("r31", AVR::R31)
-      .Case("X", AVR::R27R26).Case("Y", AVR::R29R28).Case("Z", AVR::R31R30)
+      .Case("r0", AVR::R0)
+      .Case("r1", AVR::R1)
       .Default(0);
   } else {
     Reg = StringSwitch<unsigned>(RegName)
-      .Case("r0", AVR::R1R0).Case("r2", AVR::R3R2)
-      .Case("r4", AVR::R5R4).Case("r6", AVR::R7R6)
-      .Case("r8", AVR::R9R8).Case("r10", AVR::R11R10)
-      .Case("r12", AVR::R13R12).Case("r14", AVR::R15R14)
-      .Case("r16", AVR::R17R16).Case("r18", AVR::R19R18)
-      .Case("r20", AVR::R21R20).Case("r22", AVR::R23R22)
-      .Case("r24", AVR::R25R24).Case("r26", AVR::R27R26)
-      .Case("r28", AVR::R29R28).Case("r30", AVR::R31R30)
-      .Case("X", AVR::R27R26).Case("Y", AVR::R29R28).Case("Z", AVR::R31R30)
+      .Case("r0", AVR::R1R0)
+      .Case("sp", AVR::SP)
       .Default(0);
   }
 
   if (Reg)
     return Reg;
 
-  report_fatal_error("Invalid register name global variable");
+  report_fatal_error(Twine("Invalid register name \"" + StringRef(RegName) + "\"."));
 }
 
 } // end of namespace llvm
Index: llvm/test/CodeGen/AVR/intrinsics/named-reg-alloc.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AVR/intrinsics/named-reg-alloc.ll
@@ -0,0 +1,12 @@
+; RUN: not --crash llc -O0 < %s -march=avr 2>&1 | FileCheck %s
+
+define void @foo() {
+entry:
+; CHECK: Invalid register name "r28".
+  %val1 = call i8 @llvm.read_register.i8(metadata !0)
+  ret void
+}
+
+declare i8 @llvm.read_register.i8(metadata)
+
+!0 = !{!"r28"}
Index: llvm/test/CodeGen/AVR/intrinsics/named-reg-special.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AVR/intrinsics/named-reg-special.ll
@@ -0,0 +1,42 @@
+; RUN: llc -O0 < %s -march=avr | FileCheck %s
+
+; CHECK-LABEL: read_sp:
+; CHECK: in r24, 61
+; CHECK: in r25, 62
+define i16 @read_sp() {
+entry:
+  %sp = call i16 @llvm.read_register.i16(metadata !0)
+  ret i16 %sp
+}
+
+; CHECK-LABEL: read_r0:
+; CHECK: mov r24, r0
+define i8 @read_r0() {
+entry:
+  %r0 = call i8 @llvm.read_register.i8(metadata !1)
+  ret i8 %r0
+}
+
+; CHECK-LABEL: read_r1:
+; CHECK: mov r24, r1
+define i8 @read_r1() {
+entry:
+  %r1 = call i8 @llvm.read_register.i8(metadata !2)
+  ret i8 %r1
+}
+
+; CHECK-LABEL: read_r1r0:
+; CHECK: mov r24, r0
+; CHECK: mov r25, r1
+define i16 @read_r1r0() {
+entry:
+  %r1r0 = call i16 @llvm.read_register.i16(metadata !1)
+  ret i16 %r1r0
+}
+
+declare i16 @llvm.read_register.i16(metadata)
+declare i8 @llvm.read_register.i8(metadata)
+
+!0 = !{!"sp"}
+!1 = !{!"r0"}
+!2 = !{!"r1"}
Index: llvm/test/CodeGen/AVR/intrinsics/read_register.ll
===================================================================
--- llvm/test/CodeGen/AVR/intrinsics/read_register.ll
+++ /dev/null
@@ -1,17 +0,0 @@
-; RUN: llc -O0 < %s -march=avr | FileCheck %s
-
-; CHECK-LABEL: foo
-define void @foo() {
-entry:
-  %val1 = call i16 @llvm.read_register.i16(metadata !0)
-  %val2 = call i16 @llvm.read_register.i16(metadata !1)
-  %val3 = call i8 @llvm.read_register.i8(metadata !2)
-  ret void
-}
-
-declare i8 @llvm.read_register.i8(metadata)
-declare i16 @llvm.read_register.i16(metadata)
-
-!0 = !{!"r28"}
-!1 = !{!"Z"}
-!2 = !{!"r0"}