[Xtensa] Implement sextload i8 (#106053)

Author: andreisfr

llvm/lib/Target/Xtensa/XtensaISelLowering.cpp

@@ -70,11 +70,12 @@ XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::FP_TO_UINT, MVT::i32, Expand);
   setOperationAction(ISD::FP_TO_SINT, MVT::i32, Expand);
 
-  // No sign extend instructions for i1
+  // No sign extend instructions for i1 and sign extend load i8
   for (MVT VT : MVT::integer_valuetypes()) {
     setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i1, Promote);
     setLoadExtAction(ISD::ZEXTLOAD, VT, MVT::i1, Promote);
     setLoadExtAction(ISD::EXTLOAD, VT, MVT::i1, Promote);
+    setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i8, Expand);
   }
 
   setOperationAction(ISD::ConstantPool, PtrVT, Custom);

llvm/test/CodeGen/Xtensa/load.ll

@@ -0,0 +1,12 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc --mtriple=xtensa < %s | FileCheck %s
+
+define signext i8 @test_load_i8(ptr %p){
+; CHECK-LABEL: test_load_i8:
+; CHECK:         l8ui a8, a2, 0
+; CHECK-NEXT:    slli a8, a8, 24
+; CHECK-NEXT:    srai a2, a8, 24
+; CHECK-NEXT:    ret
+  %1 = load i8, ptr %p, align 1
+  ret i8 %1
+}