[llvm] PreISelIntrinsicLowering: Lower llvm.exp/llvm.exp2 to a loop if scalable vec arg (PR #117568)

[Matt Arsenault via llvm-commits]

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@@ -453,6 +454,21 @@ bool PreISelIntrinsicLowering::lowerIntrinsics(Module &M) const {
     case Intrinsic::objc_sync_exit:
       Changed |= lowerObjCCall(F, "objc_sync_exit");
       break;
+    case Intrinsic::exp:
+    case Intrinsic::exp2:
+      Changed |= forEachCall(F, [&](CallInst *CI) {
+        unsigned Op = ISD::FEXP;
+        if (F.getIntrinsicID() == Intrinsic::exp2)
+          Op = ISD::FEXP2;
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arsenm wrote:

Should move this to a helper function that's a switch over the intrinsic ID to the ISD node. I would hope we already had such a thing available to use, but the closest thing is in BasicTTI. Later we should probably move that into TLI 

https://github.com/llvm/llvm-project/pull/117568