This reverts commit 40986feda8b1437ed475b144d5b9a208b008782a.

Reapply with fix to prevent temporary Twine from going out of scope.

Reverts llvm/llvm-project#119485

Breaks builders, details in llvm/llvm-project#119485

Currently LLVMContext::emitError emits any error as an "inline asm"
error which does not make any sense. InlineAsm appears to be special,
in that it uses a "LocCookie" from srcloc metadata, which looks like
a parallel mechanism to ordinary source line locations. This meant
that other types of failures had degraded source information reported
when available.

Introduce some new generic error types, and only use inline asm
in the appropriate contexts. The DiagnosticInfo types are still
a bit of a mess, and I'm not sure why DiagnosticInfoWithLocationBase
exists instead of just having an optional DiagnosticLocation in the
base class.

DK_Generic is for any error that derives from an IR level instruction,
and thus can pull debug locations directly from it. DK_GenericWithLoc
is functionally the generic codegen error, since it does not depend
on the IR and instead can construct a DiagnosticLocation from the
MI debug location.

Credits: https://github.com/llvm/llvm-project/pull/111419

Fixes icmp-flags.mir

First attempt: https://github.com/llvm/llvm-project/pull/113090

Revert: https://github.com/llvm/llvm-project/pull/114256

Reverts llvm/llvm-project#113090

Credits: https://github.com/llvm/llvm-project/pull/111419

Merge GlobalISel's isTriviallyDead and DeadMachineInstructionElim's
isDead code and remove all unnecessary checks from the hot path by
looping over the operands before doing any other checks.

See #105950 for why DeadMIElim needs to remove LIFETIME markers even
though they probably shouldn't generally be considered dead.

x86 CTMark O3: -0.1%
AArch64 GlobalISel CTMark O0: -0.6%, O2: -0.2%

Reverts llvm/llvm-project#106404

Breaks:
https://lab.llvm.org/buildbot/#/builders/169/builds/2590
https://lab.llvm.org/buildbot/#/builders/164/builds/2454