[PowerPC] Support conversion between f16 and f128 (#130158)

Enables conversion between f16 and f128.
Expanding on pre-Power9 targets and using HW instructions on Power9.

Fixes #92866
Commandeer of:  #97677

---------

Co-authored-by: esmeyi <[email protected]>

Author: lei137

llvm/lib/IR/RuntimeLibcalls.cpp

@@ -82,6 +82,7 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT) {
     setLibcallName(RTLIB::POWI_F128, "__powikf2");
     setLibcallName(RTLIB::FPEXT_F32_F128, "__extendsfkf2");
     setLibcallName(RTLIB::FPEXT_F64_F128, "__extenddfkf2");
+    setLibcallName(RTLIB::FPROUND_F128_F16, "__trunckfhf2");
     setLibcallName(RTLIB::FPROUND_F128_F32, "__trunckfsf2");
     setLibcallName(RTLIB::FPROUND_F128_F64, "__trunckfdf2");
     setLibcallName(RTLIB::FPTOSINT_F128_I32, "__fixkfsi");

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -223,13 +223,19 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
     setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i8, Expand);
   }
 
+  setTruncStoreAction(MVT::f128, MVT::f16, Expand);
+  setOperationAction(ISD::FP_TO_FP16, MVT::f128, Expand);
+
   if (Subtarget.isISA3_0()) {
+    setLoadExtAction(ISD::EXTLOAD, MVT::f128, MVT::f16, Legal);
     setLoadExtAction(ISD::EXTLOAD, MVT::f64, MVT::f16, Legal);
     setLoadExtAction(ISD::EXTLOAD, MVT::f32, MVT::f16, Legal);
     setTruncStoreAction(MVT::f64, MVT::f16, Legal);
     setTruncStoreAction(MVT::f32, MVT::f16, Legal);
   } else {
     // No extending loads from f16 or HW conversions back and forth.
+    setLoadExtAction(ISD::EXTLOAD, MVT::f128, MVT::f16, Expand);
+    setOperationAction(ISD::FP16_TO_FP, MVT::f128, Expand);
     setLoadExtAction(ISD::EXTLOAD, MVT::f64, MVT::f16, Expand);
     setOperationAction(ISD::FP16_TO_FP, MVT::f64, Expand);
     setOperationAction(ISD::FP_TO_FP16, MVT::f64, Expand);

llvm/lib/Target/PowerPC/PPCInstrVSX.td

@@ -3995,6 +3995,8 @@ defm : ScalToVecWPermute<
   (SUBREG_TO_REG (i64 1), (VEXTSH2Ds (LXSIHZX ForceXForm:$src)), sub_64)>;
 
 // Load/convert and convert/store patterns for f16.
+def : Pat<(f128 (extloadf16 ForceXForm:$src)),
+          (f128 (XSCVDPQP (XSCVHPDP (LXSIHZX ForceXForm:$src))))>;
 def : Pat<(f64 (extloadf16 ForceXForm:$src)),
           (f64 (XSCVHPDP (LXSIHZX ForceXForm:$src)))>;
 def : Pat<(truncstoref16 f64:$src, ForceXForm:$dst),
@@ -4003,6 +4005,8 @@ def : Pat<(f32 (extloadf16 ForceXForm:$src)),
           (f32 (COPY_TO_REGCLASS (XSCVHPDP (LXSIHZX ForceXForm:$src)), VSSRC))>;
 def : Pat<(truncstoref16 f32:$src, ForceXForm:$dst),
           (STXSIHX (XSCVDPHP (COPY_TO_REGCLASS $src, VSFRC)), ForceXForm:$dst)>;
+def : Pat<(f128 (f16_to_fp i32:$A)),
+          (f128 (XSCVDPQP (XSCVHPDP (MTVSRWZ $A))))>;
 def : Pat<(f64 (f16_to_fp i32:$A)),
           (f64 (XSCVHPDP (MTVSRWZ $A)))>;
 def : Pat<(f32 (f16_to_fp i32:$A)),