[llvm] [SelectionDAG] Remove UnsafeFPMath check in `visitFADDForFMACombine` (PR #127770)

[via llvm-commits]

================
@@ -1,18 +1,16 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=arm64 -fp-contract=fast -o - %s | FileCheck %s
+; RUN: llc -mtriple=arm64 -o - %s | FileCheck %s
 
 
 ; Make sure we don't try to fold an fneg into +0.0, creating an illegal constant
 ; -0.0. It's also good, though not essential, that we don't resort to a litpool.
 define double @test_fms_fold(double %a, double %b) {
 ; CHECK-LABEL: test_fms_fold:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    movi d2, #0000000000000000
-; CHECK-NEXT:    fmul d1, d1, d2
-; CHECK-NEXT:    fnmsub d0, d0, d2, d1
+; CHECK-NEXT:    movi {{d[0-9]+}}, #0000000000000000
 ; CHECK-NEXT:    ret
-  %mul = fmul double %a, 0.000000e+00
-  %mul1 = fmul double %b, 0.000000e+00
+  %mul = fmul fast double %a, 0.000000e+00
+  %mul1 = fmul fast double %b, 0.000000e+00
----------------
paperchalice wrote:

I think this test case should keep fast here, because the initial version of this test is
```
; RUN: llc -mtriple=arm64 -fp-contract=fast -o - %s | FileCheck %s


; Make sure we don't try to fold an fneg into +0.0, creating an illegal constant
; -0.0. It's also good, though not essential, that we don't resort to a litpool.
define double @test_fms_fold(double %a, double %b) {
; CHECK-LABEL: test_fms_fold:
; CHECK: fmov {{d[0-9]+}}, xzr
; CHECK: ret
  %mul = fmul double %a, 0.000000e+00
  %mul1 = fmul double %b, 0.000000e+00
  %sub = fsub double %mul, %mul1
  ret double %sub
}
```
which ensures constant folding do not generate -0.0 on arm.

https://github.com/llvm/llvm-project/pull/127770