Update rule for the label value for handling zero value

riscv-elf.adoc

@@ -1621,9 +1621,11 @@ scheme as the "Function types" mangling rule defined in the _Itanium {Cpp} ABI_
 defined in the _Itanium {Cpp} ABI_.
 
 The label value is derived from the lower 20 bits of the MD5 hash result of the
-function signature string. If the lower 20 bits are all zeros, the higher 20
-bits are used. If all 32 bits are zeros, the lower 20 bits of the MD5 hash
-result of the string "RISC-V" are used.
+function signature string. If the lower 20 bits are all zeros, use the next
+20 bits, and continue using the next 20 bits until a non-zero value is obtained.
+If less than 20 bits are available in the final segment, the highest 20 bits of
+the MD5 hash result will be used. If all 128 bits are zeros, the lower 20 bits
+of the MD5 hash result of the string "RISC-V" are used.
 
 Additionally, here are a few specific rules: