[llvm] [clang] [clang-tools-extra] [PowerPC] Implement llvm.set.rounding intrinsic (PR #67302)

[Chen Zheng via cfe-commits]

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@@ -8900,6 +8900,82 @@ SDValue PPCTargetLowering::LowerINT_TO_FP(SDValue Op,
   return FP;
 }
 
+SDValue PPCTargetLowering::LowerSET_ROUNDING(SDValue Op,
+                                             SelectionDAG &DAG) const {
+  SDLoc Dl(Op);
+  MachineFunction &MF = DAG.getMachineFunction();
+  EVT PtrVT = getPointerTy(MF.getDataLayout());
+  SDValue Chain = Op.getOperand(0);
+
+  // If requested mode is constant, just use simpler mtfsb.
+  if (auto *CVal = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
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chenzheng1030 wrote:

Can we use `DAG.computeKnownBits()` to handle more cases instead of just the constant inputs?

https://github.com/llvm/llvm-project/pull/67302