[MC] Remove UseAssemblerInfoForParsing

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

1 files changed, 0 insertions, 3 deletions

diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index 807071a..506e4f2 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -569,9 +569,6 @@ int main(int argc, char **argv) {
       Str->initSections(true, *STI);
   }
 
-  // Use Assembler information for parsing.
-  Str->setUseAssemblerInfoForParsing(true);
-
   int Res = 1;
   bool disassemble = false;
   switch (Action) {