[PowerPC] Add missing handling for half precision

The fix for PR39865 took care of some of the handling for half precision
but it missed a number of issues that still exist. This patch fixes the
remaining issues that cause crashes in the PPC back end.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=45776

Differential revision: https://reviews.llvm.org/D79283

Author: nemanja-ibm

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -10755,6 +10755,7 @@ SDValue PPCTargetLowering::LowerFP_EXTEND(SDValue Op, SelectionDAG &DAG) const {
   assert(Op.getOpcode() == ISD::FP_EXTEND &&
          "Should only be called for ISD::FP_EXTEND");
 
+  // FIXME: handle extends from half precision float vectors on P9.
   // We only want to custom lower an extend from v2f32 to v2f64.
   if (Op.getValueType() != MVT::v2f64 ||
       Op.getOperand(0).getValueType() != MVT::v2f32)
@@ -10968,6 +10969,11 @@ void PPCTargetLowering::ReplaceNodeResults(SDNode *N,
   case ISD::BITCAST:
     // Don't handle bitcast here.
     return;
+  case ISD::FP_EXTEND:
+    SDValue Lowered = LowerFP_EXTEND(SDValue(N, 0), DAG);
+    if (Lowered)
+      Results.push_back(Lowered);
+    return;
   }
 }
 

llvm/lib/Target/PowerPC/PPCISelLowering.h

@@ -640,7 +640,7 @@ namespace llvm {
     /// then the VPERM for the shuffle. All in all a very slow sequence.
     TargetLoweringBase::LegalizeTypeAction getPreferredVectorAction(MVT VT)
       const override {
-      if (VT.getScalarSizeInBits() % 8 == 0)
+      if (VT.getVectorNumElements() != 1 && VT.getScalarSizeInBits() % 8 == 0)
         return TypeWidenVector;
       return TargetLoweringBase::getPreferredVectorAction(VT);
     }

llvm/lib/Target/PowerPC/PPCInstrVSX.td

@@ -3658,6 +3658,13 @@ def : Pat<(f32 (extloadf16 xoaddr:$src)),
           (f32 (COPY_TO_REGCLASS (XSCVHPDP (LXSIHZX xoaddr:$src)), VSSRC))>;
 def : Pat<(truncstoref16 f32:$src, xoaddr:$dst),
           (STXSIHX (XSCVDPHP (COPY_TO_REGCLASS $src, VSFRC)), xoaddr:$dst)>;
+def : Pat<(f64 (f16_to_fp i32:$A)),
+          (f64 (XSCVHPDP (MTVSRWZ $A)))>;
+def : Pat<(f32 (f16_to_fp i32:$A)),
+          (f32 (COPY_TO_REGCLASS (XSCVHPDP (MTVSRWZ $A)), VSSRC))>;
+def : Pat<(i32 (fp_to_f16 f32:$A)),
+          (i32 (MFVSRWZ (XSCVDPHP (COPY_TO_REGCLASS $A, VSFRC))))>;
+def : Pat<(i32 (fp_to_f16 f64:$A)), (i32 (MFVSRWZ (XSCVDPHP $A)))>;
 
 // Vector sign extensions
 def : Pat<(f64 (PPCVexts f64:$A, 1)),