Follow up on #139303

(Base|Scaled)Reg may not dominate the chosen insert point, if there are
multiple uses of the address. Bail out if that's the case, otherwise we
will generate invalid IR.

In some cases, we could probably adjust the insert point or hoist the
(Base|Scaled)Reg.

Fixes https://github.com/llvm/llvm-project/issues/142830.

PR: https://github.com/llvm/llvm-project/pull/142949

Function optimizeBlock may do optimizations on a block for multiple
times. In the first iteration of the loop, MemoryInst1 may generate a
sunk instruction and store it into SunkAddrs. In the second iteration of
the loop, MemoryInst2 may use the same address and then it can reuse the
sunk instruction stored in SunkAddrs, but MemoryInst2 may be before
MemoryInst1 and the corresponding sunk instruction. In order to avoid
use before def error, we need to find appropriate insert position for the
 sunk instruction.

Fixes #138208.

The pull request discusses whether this change is needed or not. We leant
towards "it can't hurt" on the basis that it's at worst slightly unecessary
(but not incorret).

The motivation for the patch came from reviewing code duplication sites to
update for Key Instructions, finding this, trying to generate a test case and
seeing the DebugLocs aren't propagated.

Relaxes the newly added verifier rule to also allow an integer argument
to dbg_declare, which is interpreted as a pointer. Adjust CGP to deal with
it gracefully.

Fixes https://github.com/llvm/llvm-project/issues/134523.
Alternative to https://github.com/llvm/llvm-project/pull/134601.

These date back to when the non-intrinsic format of variable locations
was still being tested and was behind a compile-time flag, so not all
builds / bots would correctly run them. The solution at the time, to get
at least some test coverage, was to have tests opt-in to non-intrinsic
debug-info if it was built into LLVM.

Nowadays, non-intrinsic format is the default and has been on for more
than a year, there's no need for this flag to exist.

(I've downgraded the flag from "try" to explicitly requesting
non-intrinsic format in some places, so that we can deal with tests that
are explicitly about non-intrinsic format in their own commit).

This is a split of https://github.com/llvm/llvm-project/pull/125756

This patch contains a number of changes relating to the above flag;
primarily it updates comment references to the old flag names,
"-fextend-lifetimes" and "-fextend-this-ptr" to refer to the new names,
"-fextend-variable-liveness[={all,this}]". These changes are all NFC.

This patch also removes the explicit -fextend-this-ptr-liveness flag
alias, and shortens the help-text for the main flag; these are both
changes that were meant to be applied in the initial PR (#110000), but
due to some user-error on my part they were not included in the merged
commit.

Alive2: https://alive2.llvm.org/ce/z/pMcD7q
Closes https://github.com/llvm/llvm-project/issues/118172.