MCAsmLexer.h has been made a forwarder header since #134207

HLASM is very different from the gas syntax. We don't expect other
targets to customize the differences. Unify the numerous variables.

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.

AArch64 uses MCAsmInfo::AssemblerDialect to control the style of emitted
Neon assembly. E.g. Apple platforms use AsmWriterVariantTy::Apple by
default which collides with InlineAsm::AD_Intel (both value 1). Checking
for inlineasm dialects on non-X86 platforms can thus lead to problems.

Since `raw_string_ostream` doesn't own the string buffer, it is
desirable (in terms of memory safety) for users to directly reference
the string buffer rather than use `raw_string_ostream::str()`.

Work towards TODO comment to remove `raw_string_ostream::str()`.

Commit 6c0665e22174d474050e85ca367424f6e02476be
(https://reviews.llvm.org/D45164) enabled certain constant expression
evaluation for `MCObjectStreamer` at parse time (e.g. `.if` directives,
see llvm/test/MC/AsmParser/assembler-expressions.s).

`getUseAssemblerInfoForParsing` was added to make `clang -c` handling
inline assembly similar to `MCAsmStreamer` (e.g. `llvm-mc -filetype=asm`),
where such expression folding (related to
`AttemptToFoldSymbolOffsetDifference`) is unavailable.

I believe this is overly conservative. We can make some parse-time
expression folding work for `clang -c` even if `clang -S` would still
report an error, a MCAsmStreamer issue (we cannot print `.if`
directives) that should not restrict the functionality of
MCObjectStreamer.

```
% cat b.cc
asm(R"(
.pushsection .text,"ax"
.globl _start; _start: ret
.if . -_start == 1
  ret
.endif
.popsection
)");
% gcc -S b.cc && gcc -c b.cc
% clang -S -fno-integrated-as b.cc     # succeeded

% clang -c b.cc     # succeeded with this patch
% clang -S b.cc     # still failed
<inline asm>:4:5: error: expected absolute expression
    4 | .if . -_start == 1
      |     ^
1 error generated.
```

However, removing `getUseAssemblerInfoForParsing` would make
MCDwarfFrameEmitter::Emit (for .eh_frame FDE) slow (~4% compile time
regression for sqlite3.c amalgamation) due to expensive
`AttemptToFoldSymbolOffsetDifference`. For now, make
`UseAssemblerInfoForParsing` false in MCDwarfFrameEmitter::Emit.

Close #62520
Link: https://discourse.llvm.org/t/rfc-clang-assembly-object-equivalence-for-files-with-inline-assembly/78841

Pull Request: https://github.com/llvm/llvm-project/pull/91082

This reverts commit 03c53c69a367008da689f0d2940e2197eb4a955c.

This causes very large compile-time regressions in some cases,
e.g. sqlite3 at O0 regresses by 5%.

Commit 6c0665e22174d474050e85ca367424f6e02476be
(https://reviews.llvm.org/D45164) enabled certain constant expression
evaluation for `MCObjectStreamer` at parse time (e.g. `.if` directives,
see llvm/test/MC/AsmParser/assembler-expressions.s).

`getUseAssemblerInfoForParsing` was added to make `clang -c` handling
inline assembly similar to `MCAsmStreamer` (e.g. `llvm-mc -filetype=asm`),
where such expression folding (related to
`AttemptToFoldSymbolOffsetDifference`) is unavailable.

I believe this is overly conservative. We can make some parse-time
expression folding work for `clang -c` even if `clang -S` would still
report an error, a MCAsmStreamer issue (we cannot print `.if`
directives) that should not restrict the functionality of
MCObjectStreamer.

```
% cat b.cc
asm(R"(
.pushsection .text,"ax"
.globl _start; _start: ret
.if . -_start == 1
  ret
.endif
.popsection
)");
% gcc -S b.cc && gcc -c b.cc
% clang -S -fno-integrated-as b.cc     # succeeded

% clang -c b.cc     # succeeded with this patch
% clang -S b.cc     # still failed
<inline asm>:4:5: error: expected absolute expression
    4 | .if . -_start == 1
      |     ^
1 error generated.
```

Close #62520
Link: https://discourse.llvm.org/t/rfc-clang-assembly-object-equivalence-for-files-with-inline-assembly/78841

Pull Request: https://github.com/llvm/llvm-project/pull/91082