[RISCV][CFI] add function epilogue cfi information (#110810)

This patch adds CFI instructions in the function epilogue.

Before patch:
addi sp, s0, -32
ld ra, 24(sp) # 8-byte Folded Reload
ld s

[RISCV][CFI] add function epilogue cfi information (#110810)

This patch adds CFI instructions in the function epilogue.

Before patch:
addi sp, s0, -32
ld ra, 24(sp) # 8-byte Folded Reload
ld s0, 16(sp) # 8-byte Folded Reload
ld s1, 8(sp) # 8-byte Folded Reload
addi sp, sp, 32
ret

After patch:
addi sp, s0, -32
.cfi_def_cfa sp, 32
ld ra, 24(sp) # 8-byte Folded Reload
ld s0, 16(sp) # 8-byte Folded Reload
ld s1, 8(sp) # 8-byte Folded Reload
.cfi_restore ra
.cfi_restore s0
.cfi_restore s1
addi sp, sp, 32
.cfi_def_cfa_offset 0
ret

This functionality is already present in `riscv-gcc`, but it’s not in
`clang` and this slightly impairs the `lldb` debugging experience, e.g.
backtrace.

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[RISCV] Insert simple landing pad before indirect jumps for Zicfilp. (#91860)

This patch is based on https://github.com/llvm/llvm-project/pull/91855.
This patch inserts simple landing pad
([pr])be

[RISCV] Insert simple landing pad before indirect jumps for Zicfilp. (#91860)

This patch is based on https://github.com/llvm/llvm-project/pull/91855.
This patch inserts simple landing pad
([pr])before indirct jumps. And this also make option
riscv-landing-pad-label influence this feature.
[pr]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/417

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[RISCV] Insert simple landing pad for taken address labels. (#91855)

This patch implements simple landing pad labels ([pr]). When Zicfilp
enabled, this patch inserts `lpad 0` at the beginning of ba

[RISCV] Insert simple landing pad for taken address labels. (#91855)

This patch implements simple landing pad labels ([pr]). When Zicfilp
enabled, this patch inserts `lpad 0` at the beginning of basic blocks
which are possible to be landed by indirect jumps.
This patch also supports option riscv-landing-pad-label to make users
cpable to set nonzero fixed labels. Using nonzero fixed label force
setting t2 before indirect jumps. It's less portable but more strict
than original implementation.

[pr]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/417

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