[llvm] [ARM] Add strict uint to FP conversion handling during operation legalization (PR #208554)

[David Green via llvm-commits]

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@@ -5838,19 +5844,37 @@ static SDValue LowerVectorINT_TO_FP(SDValue Op, SelectionDAG &DAG) {
 
 SDValue ARMTargetLowering::LowerINT_TO_FP(SDValue Op, SelectionDAG &DAG) const {
   EVT VT = Op.getValueType();
-  if (VT.isVector())
+  if (VT.isVector()) {
     return LowerVectorINT_TO_FP(Op, DAG);
+  }
+
+  bool IsStrict = Op->isStrictFPOpcode();
+  SDValue SrcVal = Op.getOperand(IsStrict ? 1 : 0);
+
   if (isUnsupportedFloatingType(VT)) {
     RTLIB::Libcall LC;
-    if (Op.getOpcode() == ISD::SINT_TO_FP)
-      LC = RTLIB::getSINTTOFP(Op.getOperand(0).getValueType(),
-                              Op.getValueType());
+    if (Op.getOpcode() == ISD::SINT_TO_FP ||
+        Op.getOpcode() == ISD::STRICT_SINT_TO_FP)
+      LC = RTLIB::getSINTTOFP(SrcVal.getValueType(), Op.getValueType());
     else
-      LC = RTLIB::getUINTTOFP(Op.getOperand(0).getValueType(),
-                              Op.getValueType());
+      LC = RTLIB::getUINTTOFP(SrcVal.getValueType(), Op.getValueType());
+    SDLoc Loc(Op);
     MakeLibCallOptions CallOptions;
-    return makeLibCall(DAG, LC, Op.getValueType(), Op.getOperand(0),
-                       CallOptions, SDLoc(Op)).first;
+    SDValue Chain = IsStrict ? Op.getOperand(0) : SDValue();
+    SDValue Result;
+    std::tie(Result, Chain) = makeLibCall(DAG, LC, Op.getValueType(), SrcVal,
+                                          CallOptions, Loc, Chain);
+    return IsStrict ? DAG.getMergeValues({Result, Chain}, Loc) : Result;
+  }
+
+  // FIXME: Remove this when we have strict fp instruction selection patterns
----------------
davemgreen wrote:

> IsStrict is handled separately in order to preserve chain - would the any_sint_to_fp pattern preserve chain as well?

I believe so. I'm not sure if this version properly preserves the chain and I would expect the strict nodes to be used until selection, so that the chain can be kept in place.

https://github.com/llvm/llvm-project/pull/208554