[llvm] [SelectionDAG] Disable FastISel for swiftasync functions (PR #70741)

[Felipe de Azevedo Piovezan via llvm-commits]

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@@ -1441,11 +1441,21 @@ static void processSingleLocVars(FunctionLoweringInfo &FuncInfo,
   }
 }
 
+static bool shouldEnableFastISel(const Function &Fn) {
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felipepiovezan wrote:

AFAICT all the TargetMachine hooks operate independently of the Function being lowered.

Regarding `OptLevelChanger`, it seems to be used to force the opt level to "None" when we have `skipPass(Fn) == true`, and  then it queries the TM to check if FastISel is enabled for O0.


That said, some of the debug messages inside `OptLevelChanger` makes me think we could add move the check from this patch in there. What do you think?

https://github.com/llvm/llvm-project/pull/70741