[llvm] [VPlan] Propagate FastMathFlags from phis to blends (PR #180226)

[Luke Lau via llvm-commits]

================
@@ -2733,19 +2737,20 @@ void VPBlendRecipe::printRecipe(raw_ostream &O, const Twine &Indent,
   O << Indent << "BLEND ";
   printAsOperand(O, SlotTracker);
   O << " =";
+  printFlags(O);
----------------
lukel97 wrote:

Yeah it emits a space unconditionally, plus a space before any flag. So the output is like this for phis and blends:

```
EMIT-SCALAR ir<%phi> = phi fast [ ir<0.000000e+00>, then ], [ ir<%x>, loop ]
BLEND ir<%phi> = fast ir<%x>ir<0.000000e+00>/ir<%c>
```

https://github.com/llvm/llvm-project/pull/180226