[SelectionDAGBuilder] use bitcast instead of AnyExtOrTrunc if copy parts from an int vector to a float vector to fix issue #58615

[HazyFish]

Summary

The getCopyFromPartsVector doesn't work correctly when PartEVT and ValueVT have both different element type and different size.

This patch

1. removes the part of a comment that contains the incorrect assumption that element type are the same
2. use bitcast when copy parts of int vector to a float vector after the subvector extraction

[HazyFish]

format

[HazyFish]

format

[efriedma]

LGTM

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

static SDValue getCopyFromPartsVector(SelectionDAG &DAG, const SDLoc &DL,
   if (PartEVT == ValueVT)
     return Val;
 
   if (PartEVT.isVector()) {
     // Vector/Vector bitcast.
     if (ValueVT.getSizeInBits() == PartEVT.getSizeInBits())
       return DAG.getNode(ISD::BITCAST, DL, ValueVT, Val);
 
-    // If the element type of the source/dest vectors are the same, but the
-    // parts vector has more elements than the value vector, then we have a
-    // vector widening case (e.g. <2 x float> -> <4 x float>).  Extract the
-    // elements we want.
+    // If the parts vector has more elements than the value vector, then we
+    // have a vector widening case (e.g. <2 x float> -> <4 x float>).
+    // Extract the elements we want.
     if (PartEVT.getVectorElementCount() != ValueVT.getVectorElementCount()) {
       assert((PartEVT.getVectorElementCount().getKnownMinValue() >
               ValueVT.getVectorElementCount().getKnownMinValue()) &&
              (PartEVT.getVectorElementCount().isScalable() ==
               ValueVT.getVectorElementCount().isScalable()) &&
              "Cannot narrow, it would be a lossy transformation");
       PartEVT =
           EVT::getVectorVT(*DAG.getContext(), PartEVT.getVectorElementType(),
                            ValueVT.getVectorElementCount());
       Val = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, PartEVT, Val,
                         DAG.getVectorIdxConstant(0, DL));
       if (PartEVT == ValueVT)
         return Val;
+      if (PartEVT.isInteger() && ValueVT.isFloatingPoint())
+        return DAG.getNode(ISD::BITCAST, DL, ValueVT, Val);
     }
 
     // Promoted vector extract
     return DAG.getAnyExtOrTrunc(Val, DL, ValueVT);
   }
 
   // Trivial bitcast if the types are the same size and the destination
   // vector type is legal.

llvm/test/CodeGen/AArch64/aarch64-v1f32-arg.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=aarch64 | FileCheck %s
+
+define <1 x float> @f(<16 x i64> %0, <1 x float> %1) {
+; CHECK-LABEL: f:
+; CHECK:       // %bb.0: // %BB
+; CHECK-NEXT:    ldr d0, [sp]
+; CHECK-NEXT:    ret
+BB:
+  ret <1 x float> %1
+}