[llvm] [X86][SelectionDAG] - Add support for llvm.canonicalize intrinsic (PR #106370)

[Matt Arsenault via llvm-commits]

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@@ -1275,6 +1275,56 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
       }
     }
     break;
+    case ISD::FCANONICALIZE: {
+      const Triple &TT = DAG.getTarget().getTargetTriple();
+      if (TT.getArch() == Triple::x86 || TT.getArch() == Triple::x86_64) {
+        SDValue Operand = Node->getOperand(0);
+        SDLoc dl(Node);
+        EVT VT = Operand.getValueType();
+
+        if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(Operand)) {
+          const APFloat &C = CFP->getValueAPF();
+          if (C.isDenormal()) {
+            DenormalMode Mode =
+                DAG.getMachineFunction().getDenormalMode(C.getSemantics());
+            assert((Mode != DenormalMode::getPositiveZero()) &&
+                   "Positive denormal mode is not valid for X86 target.");
+            if (Mode == DenormalMode::getPreserveSign()) {
+              SDValue SDZero =
+                  DAG.getConstantFP((C.isNegative() ? -0.0 : 0.0), dl, VT);
+              ConstantFPSDNode *ZeroConstFP = cast<ConstantFPSDNode>(SDZero);
+              SDValue CanonZeroFPLoad = ExpandConstantFP(ZeroConstFP, true);
+              DAG.ReplaceAllUsesWith(Node, CanonZeroFPLoad.getNode());
+              LLVM_DEBUG(dbgs()
+                         << "Legalized Denormal under mode PreserveSign\n");
+              return;
+            } else if (Mode == DenormalMode::getIEEE()) {
+              DAG.ReplaceAllUsesWith(Node, Operand.getNode());
+              LLVM_DEBUG(dbgs() << "Legalized Denormal under mode IEEE\n");
+              return;
+            }
+          } else if (C.isNaN() && C.isSignaling()) {
+            APFloat CanonicalQNaN = APFloat::getQNaN(C.getSemantics());
+            SDValue QuitNaN = DAG.getConstantFP(CanonicalQNaN, dl, VT);
+            ConstantFPSDNode *QNaNConstFP = cast<ConstantFPSDNode>(QuitNaN);
+            SDValue QNanLoad = ExpandConstantFP(QNaNConstFP, true);
+            DAG.ReplaceAllUsesWith(Node, QNanLoad.getNode());
+            LLVM_DEBUG(dbgs() << "Legalized Signaling NaN to Quiet NaN\n");
+            return;
+          }
+        } else if (Operand.isUndef()) {
+          APFloat CanonicalQNaN = APFloat::getQNaN(VT.getFltSemantics());
+          SDValue QuitNaN = DAG.getConstantFP(CanonicalQNaN, dl, VT);
+          ConstantFPSDNode *QNaNConstFP = cast<ConstantFPSDNode>(QuitNaN);
+          SDValue QNanLoad = ExpandConstantFP(QNaNConstFP, true);
+          DAG.ReplaceAllUsesWith(Node, QNanLoad.getNode());
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arsenm wrote:

Shouldn't need to do any manual replacement? 

https://github.com/llvm/llvm-project/pull/106370