[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] Exploit sh3add/sh2add for stack offsets by shifted 12-bit constants (#87950)

If we're falling back to generic constant formation in a register +
add/sub, we can check if we have a constant

[RISCV] Exploit sh3add/sh2add for stack offsets by shifted 12-bit constants (#87950)

If we're falling back to generic constant formation in a register +
add/sub, we can check if we have a constant which is 12-bits but left
shifted by 2 or 3. If so, we can use a sh2add or sh3add to perform the
shift and add in a single instruction.

This is profitable when the unshifted constant would require two
instructions (LUI/ADDI) to form, but is never harmful since we're going
to need at least two instructions regardless of the constant value.

Since stacks are aligned to 16 bytes by default, sh3add allows addresing
(aligned) data out to 2^14 (i.e. 16kb) in at most two instructions
w/zba.

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[RISCV] Expand test coverage of stack offsets between 2^11 and 2^15

Adds two sets of tests. First, one for prolog/epilogue insertions where
the second stack adjustment can be done with shNadd for z

[RISCV] Expand test coverage of stack offsets between 2^11 and 2^15

Adds two sets of tests. First, one for prolog/epilogue insertions where
the second stack adjustment can be done with shNadd for zba. Second, a
set of tests with offsets off SP in the same ranges, but also adding
varying alignments.

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