# Implementation

    class Helper:
        def __init__(self, XLEN):
            self.XLEN = XLEN

        def EXTSXL(self, value, bits):
            bits = min(bits, self.XLEN) # strangely this is redundant
            return SelectableInt(exts(value.value, bits), self.XLEN)

# Table

[[!table  data="""
func |pcode              |
extsb|RA <- EXTSX(RS, 8) |
extsh|RA <- EXTSX(RS, 16)|
extsw|RA <- EXTSX(RS, 32)|
"""]]

# Examples in tabular form

these should contain *desired and expected* answers, **not** what the **code**
says "this is the answer if you run this code on these values".
They are also CSV files which the openpower-isa unit tests can
run to confirm the implementation is correct.

0xA000000090000A93
[[!table format=csv file="openpower/isafunctions/extsxl_0xA000000090000A93.csv"]]

0x0000000090000A93
[[!table format=csv file="openpower/isafunctions/extsxl_0x0000000090000A93.csv"]]

0x000000000000F074
[[!table format=csv file="openpower/isafunctions/extsxl_0x000000000000F074.csv"]]

0x0000000000000091
[[!table format=csv file="openpower/isafunctions/extsxl_0x0000000000000091.csv"]]

0x9999999999999999
[[!table format=csv file="openpower/isafunctions/extsxl_0x9999999999999999.csv"]]

0x1111111111111111
[[!table format=csv file="openpower/isafunctions/extsxl_0x1111111111111111.csv"]]

# Examples

    for xlen in (8, 16, 32, 64):
        helper = Helper(xlen)
        REG = lambda v: SelectableInt(v, xlen)

        assert helper.EXTSXL(REG(0xA000000090000A93), 64) == REG(0xA000000090000a93)
        assert helper.EXTSXL(REG(0x0000000090000A93), 32) == REG(0xffffffff90000a93)
        assert helper.EXTSXL(REG(0x000000000000F074), 16) == REG(0xfffffffffffff074)
        assert helper.EXTSXL(REG(0x0000000000000091),  8) == REG(0xffffffffffffff91)

        assert helper.EXTSXL(REG(0x7000000090000A93), 64) == REG(0x7000000090000a93)
        assert helper.EXTSXL(REG(0x0000000050000A93), 32) == REG(0x50000a93)
        assert helper.EXTSXL(REG(0x0000000000001074), 16) == REG(0x1074)
        assert helper.EXTSXL(REG(0x0000000000000031),  8) == REG(0x31)

        assert helper.EXTSXL(REG(0xA000000090000A93), 64) == REG(0xA000000090000a93)
        assert helper.EXTSXL(REG(0x0000000090000A93), 64) == REG(0x90000a93)
        assert helper.EXTSXL(REG(0x000000000000F074), 32) == REG(0xf074)
        assert helper.EXTSXL(REG(0x0000000000000091), 16) == REG(0x91)

        assert helper.EXTSXL(REG(0x9999999999999999), 64) == REG(0x9999999999999999)
        assert helper.EXTSXL(REG(0x9999999999999999), 32) == REG(0xFFFFFFFF99999999)
        assert helper.EXTSXL(REG(0x9999999999999999), 16) == REG(0xFFFFFFFFFFFF9999)
        assert helper.EXTSXL(REG(0x9999999999999999),  8) == REG(0xFFFFFFFFFFFFFF99)