[AVR] Promote i1 ZEXTs to i8

Previously, this would cause an ISel error.

Author: Dylan McKay

lib/Target/AVR/AVRISelLowering.cpp

@@ -51,9 +51,10 @@ AVRTargetLowering::AVRTargetLowering(AVRTargetMachine &tm)
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i16, Expand);
 
   for (MVT VT : MVT::integer_valuetypes()) {
-    setLoadExtAction(ISD::EXTLOAD, VT, MVT::i8, Expand);
-    setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i8, Expand);
-    setLoadExtAction(ISD::ZEXTLOAD, VT, MVT::i8, Expand);
+    for (auto N : {ISD::EXTLOAD, ISD::SEXTLOAD, ISD::ZEXTLOAD}) {
+      setLoadExtAction(N, VT, MVT::i1, Promote);
+      setLoadExtAction(N, VT, MVT::i8, Expand);
+    }
   }
 
   setTruncStoreAction(MVT::i16, MVT::i8, Expand);

test/CodeGen/AVR/zext.ll

@@ -19,3 +19,13 @@ define i16 @zext2(i8 %x, i8 %y) {
   %1 = zext i8 %y to i16
   ret i16 %1
 }
+
+; zext R25:R24, R24
+; eor R25, R25
+define i16 @zext_i1(i1 %x) {
+; CHECK-LABEL: zext_i1:
+; CHECK: eor r25, r25
+  %1 = zext i1 %x to i16
+  ret i16 %1
+}
+