Question

Write a short RISC-V assembly program that operates on a NULL terminated string of arbitrary size (use your favourite phrase when you define it with DC for testing). The program (no need to define a function) scans the string and replaces every lower case character with the corresponding upper case. Your program prints the string before and after converting it to upper case.

Answer 1

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PROGRAM

convertOpposite(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&):

        addi    sp,sp,-32

        sd      s0,24(sp)

        addi    s0,sp,32

        sd      a0,-24(s0)

        nop

        ld      s0,24(sp)

        addi    sp,sp,32

        jr      ra

.LC0:

        .string "Enter the string  :  "

.LC1:

        .string "\nResultant String :  "

main:

        addi    sp,sp,-80

        sd      ra,72(sp)

        sd      s0,64(sp)

        sd      s1,56(sp)

        addi    s0,sp,80

        addi    a5,s0,-72

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string() [complete object constructor]

        lui     a5,%hi(.LC0)

        addi    a1,a5,%lo(.LC0)

        lui     a5,%hi(_ZSt4cout)

        addi    a0,a5,%lo(_ZSt4cout)

        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)

        addi    a5,s0,-72

        mv      a1,a5

        lui     a5,%hi(_ZSt3cin)

        addi    a0,a5,%lo(_ZSt3cin)

        call    std::basic_istream<char, std::char_traits<char> >& std::operator>><char, std::char_traits<char>, std::allocator<char> >(std::basic_istream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&)

        addi    a5,s0,-72

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::length() const

        mv      a5,a0

        sw      a5,-40(s0)

        sw      zero,-36(s0)

.L10:

        lw      a4,-36(s0)

        lw      a5,-40(s0)

        sext.w  a4,a4

        sext.w  a5,a5

        bge     a4,a5,.L3

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     a5,0(a5)

        mv      a4,a5

        li      a5,96

        bleu    a4,a5,.L4

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     a5,0(a5)

        mv      a4,a5

        li      a5,122

        bgtu    a4,a5,.L4

        li      a5,1

        j       .L5

.L4:

        li      a5,0

.L5:

        beqz    a5,.L6

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     s1,0(a5)

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a4,a0

        addiw   a5,s1,-32

        andi    a5,a5,0xff

        sb      a5,0(a4)

        j       .L7

.L6:

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     a5,0(a5)

        mv      a4,a5

        li      a5,64

        bleu    a4,a5,.L8

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     a5,0(a5)

        mv      a4,a5

        li      a5,90

        bgtu    a4,a5,.L8

        li      a5,1

        j       .L9

.L8:

        li      a5,0

.L9:

        beqz    a5,.L7

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a5,a0

        lbu     s1,0(a5)

        lw      a4,-36(s0)

        addi    a5,s0,-72

        mv      a1,a4

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long)

        mv      a4,a0

        addiw   a5,s1,32

        andi    a5,a5,0xff

        sb      a5,0(a4)

.L7:

        lw      a5,-36(s0)

        addiw   a5,a5,1

        sw      a5,-36(s0)

        j       .L10

.L3:

        lui     a5,%hi(.LC1)

        addi    a1,a5,%lo(.LC1)

        lui     a5,%hi(_ZSt4cout)

        addi    a0,a5,%lo(_ZSt4cout)

        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)

        mv      a4,a0

        addi    a5,s0,-72

        mv      a1,a5

        mv      a0,a4

        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

        li      s1,0

        addi    a5,s0,-72

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() [complete object destructor]

        mv      a5,s1

        j       .L14

        mv      s1,a0

        addi    a5,s0,-72

        mv      a0,a5

        call    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() [complete object destructor]

        mv      a5,s1

        mv      a0,a5

        call    _Unwind_Resume

.L14:

        mv      a0,a5

        ld      ra,72(sp)

        ld      s0,64(sp)

        ld      s1,56(sp)

        addi    sp,sp,80

        jr      ra

__static_initialization_and_destruction_0(int, int):

        addi    sp,sp,-32

        sd      ra,24(sp)

        sd      s0,16(sp)

        addi    s0,sp,32

        mv      a5,a0

        mv      a4,a1

        sw      a5,-20(s0)

        mv      a5,a4

        sw      a5,-24(s0)

        lw      a5,-20(s0)

        sext.w  a4,a5

        li      a5,1

        bne     a4,a5,.L17

        lw      a5,-24(s0)

        sext.w  a4,a5

        li      a5,65536

        addi    a5,a5,-1

        bne     a4,a5,.L17

        lui     a5,%hi(_ZStL8__ioinit)

        addi    a0,a5,%lo(_ZStL8__ioinit)

        call    std::ios_base::Init::Init() [complete object constructor]

        lui     a5,%hi(__dso_handle)

        addi    a2,a5,%lo(__dso_handle)

        lui     a5,%hi(_ZStL8__ioinit)

        addi    a1,a5,%lo(_ZStL8__ioinit)

        lui     a5,%hi(_ZNSt8ios_base4InitD1Ev)

        addi    a0,a5,%lo(_ZNSt8ios_base4InitD1Ev)

        call    __cxa_atexit

.L17:

        nop

        ld      ra,24(sp)

        ld      s0,16(sp)

        addi    sp,sp,32

        jr      ra

_GLOBAL__sub_I_convertOpposite(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&):

        addi    sp,sp,-16

        sd      ra,8(sp)

        sd      s0,0(sp)

        addi    s0,sp,16

        li      a5,65536

        addi    a1,a5,-1

        li      a0,1

        call    __static_initialization_and_destruction_0(int, int)

        ld      ra,8(sp)

        ld      s0,0(sp)

        addi    sp,sp,16

        jr      ra

DW.ref.__gxx_personality_v0:

IMAGE OF OUTPUT