[llvm] [X86] Lower mathlib call ldexp into scalef when avx512 is enabled (PR #69710)

[Simon Pilgrim via llvm-commits]

================
@@ -31814,6 +31820,45 @@ static StringRef getInstrStrFromOpNo(const SmallVectorImpl<StringRef> &AsmStrs,
   return StringRef();
 }
 
+static SDValue LowerFLDEXP(SDValue Op, SelectionDAG &DAG) {
+  SDValue X = Op.getOperand(0);
+  EVT XScalarTy = X.getValueType();
+  SDValue Exp = Op.getOperand(1);
+
+  SDLoc DL(Op);
+  EVT XVT, ExpVT;
+  SDValue IID;
+  switch (Op.getSimpleValueType().SimpleTy) {
+  default:
+    return SDValue();
+  case MVT::f16:
+    X = DAG.getNode(ISD::FP_EXTEND, DL, MVT::f32, X);
+    [[fallthrough]];
+  case MVT::f32:
+    XVT = MVT::v4f32;
+    ExpVT = MVT::v4f32;
+    break;
+  case MVT::f64:
+    XVT = MVT::v2f64;
+    ExpVT = MVT::v2f64;
+    break;
+  }
+
+  SDValue Zero = DAG.getConstant(0, DL, MVT::i64);
+  Exp = DAG.getNode(ISD::SINT_TO_FP, DL, X.getValueType(), Exp);
+  SDValue VX =
+      DAG.getNode(ISD::INSERT_VECTOR_ELT, DL, XVT, DAG.getUNDEF(XVT), X, Zero);
+  SDValue VExp = DAG.getNode(ISD::INSERT_VECTOR_ELT, DL, ExpVT,
+                             DAG.getUNDEF(ExpVT), Exp, Zero);
+  SDValue Scalef = DAG.getNode(X86ISD::SCALEFS, DL, XVT, VX, VExp, VX);
----------------
RKSimon wrote:

Why do you need to vectorize to use SCALEFS? I thought SCALEFS was for scalar types and SCALEF was for vector types? (So it should be possible to add vector support here as well).

https://github.com/llvm/llvm-project/pull/69710