When assertions are enabled it is impossible to construct a
`string_view` which contains a null pointer and a non-zero size, so
assertions where we check for that on an already constructed
`string_view` are unreachable.

This fold optimizes 

```llvm
define i1 @src(i32 %num, i32 %val) {
  %mask = add i32 %val, -1
  %neg = sub nsw i32 0, %val

  %num.biased = add i32 %num, %mask
  %_2.sroa.0.0 = and i32 %num.biased, %neg
  %_0 = icmp eq i32 %_2.sroa.0.0, %num
  ret i1 %_0
}
```
to
```llvm
define i1 @tgt(i32 %num, i32 %val) {
  %mask = add i32 %val, -1
  %tmp = and i32 %num, %mask
  %ret = icmp eq i32 %tmp, 0
  ret i1 %ret
}
```

For power-of-two `val`.

Observed in real life for following code

```rust
pub fn is_aligned(num: usize) -> bool {
    num.next_multiple_of(1 << 12) == num
}
```
which verifies that num is aligned to 4096.

Alive2 proof https://alive2.llvm.org/ce/z/QisECm

Change dominator tree updates to also handle post dominator tree.

Depend on #152591 to fix
https://github.com/llvm/llvm-project/issues/149023.
Similar to an EH pad, there is no real advantage in "falling through" to
an indirect target of an INLINEASM_BR. And multiple indirect targets of
inline asm at the end of a function may be rotated infinitely.
Therefore, this patch avoids such optimization on indirect target of
inline asm as fall through.

This patch adds CodeGen support for qc.insbi and qc.insb instructions
defined in the Qualcomm uC Xqcibm extension. qc.insbi and qc.insb
inserts bits into destination register from immediate and register
operand respectively.
A sequence of `xor`, `and` & `xor` depending on appropriate conditions
are converted to `qc.insbi` or `qc.insb` which depends on the
immediate's value.

Close https://github.com/llvm/llvm-project/issues/138558

The compiler failed to understand the redeclaration-relationship when
performing checks when MergeFunctionDecl. This seemed to be a complex
circular problem (how can we know the redeclaration relationship before
performing merging?). But the fix seems to be easy and safe. It is fine
to only perform the check only if the using decl is a local decl.