Added negative offset case for JALR

tests/jalr.s

@@ -12,17 +12,19 @@ _start:
     # Try to call two imbricated functions
     jal fn0
 
+    # Jump to 'just_after'
     auipc ra, 0
-    jalr 12(ra)
+    jalr 16(ra)
+
+    # Jump far to test jalr with negative offset
+    jal fnfar
 
     ebreak
 
-# just_after : address is 12 bytes after auipc
+# just_after : address is 16 bytes after auipc
 just_after:
     # ra must still be the old address
-    addi a0, zero, 0
     ret
-    addi a0, zero, 1
     ebreak
 
 # fn0 : function that calls fn1 and returns
@@ -46,3 +48,12 @@ fn0:
 fn1:
     ret
     ebreak
+
+fnneg:
+    addi a0, zero, 0
+    ebreak
+
+fnfar:
+    auipc ra, 0
+    jalr -8(ra)
+    ebreak