[Power9] Ensure float128 in non-homogenous aggregates are passed via VSX reg

Non-homogenous aggregates are passed in consecutive GPRs, in GPRs and in memory,
or in memory. This patch ensures that float128 members of non-homogenous
aggregates are passed via VSX registers.

This is done via custom lowering a bitcast of a build_pari(i64,i64) to float128
to a new PPCISD node, BUILD_FP128.

Differential Revision: https://reviews.llvm.org/D48308

llvm-svn: 336310

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -814,6 +814,7 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
         setOperationAction(ISD::FP_ROUND, MVT::f32, Legal);
         setTruncStoreAction(MVT::f128, MVT::f64, Expand);
         setTruncStoreAction(MVT::f128, MVT::f32, Expand);
+        setOperationAction(ISD::BITCAST, MVT::i128, Custom);
       }
 
     }
@@ -1268,6 +1269,7 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
   case PPCISD::QVESPLATI:       return "PPCISD::QVESPLATI";
   case PPCISD::QBFLT:           return "PPCISD::QBFLT";
   case PPCISD::QVLFSb:          return "PPCISD::QVLFSb";
+  case PPCISD::BUILD_FP128:     return "PPCISD::BUILD_FP128";
   }
   return nullptr;
 }
@@ -7661,6 +7663,23 @@ static bool haveEfficientBuildVectorPattern(BuildVectorSDNode *V,
   return !(IsSplat && IsLoad);
 }
 
+// Lower BITCAST(f128, (build_pair i64, i64)) to BUILD_FP128.
+SDValue PPCTargetLowering::LowerBITCAST(SDValue Op, SelectionDAG &DAG) const {
+
+  SDLoc dl(Op);
+  SDValue Op0 = Op->getOperand(0);
+
+  if (!EnableQuadPrecision ||
+      (Op.getValueType() != MVT::f128 ) ||
+      (Op0.getOpcode() != ISD::BUILD_PAIR) ||
+      (Op0.getOperand(0).getValueType() !=  MVT::i64) ||
+      (Op0.getOperand(1).getValueType() != MVT::i64))
+    return SDValue();
+
+  return DAG.getNode(PPCISD::BUILD_FP128, dl, MVT::f128, Op0.getOperand(0),
+                     Op0.getOperand(1));
+}
+
 // If this is a case we can't handle, return null and let the default
 // expansion code take care of it.  If we CAN select this case, and if it
 // selects to a single instruction, return Op.  Otherwise, if we can codegen
@@ -9455,6 +9474,8 @@ SDValue PPCTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   // For counter-based loop handling.
   case ISD::INTRINSIC_W_CHAIN:  return SDValue();
 
+  case ISD::BITCAST:            return LowerBITCAST(Op, DAG);
+
   // Frame & Return address.
   case ISD::RETURNADDR:         return LowerRETURNADDR(Op, DAG);
   case ISD::FRAMEADDR:          return LowerFRAMEADDR(Op, DAG);

llvm/lib/Target/PowerPC/PPCISelLowering.h

@@ -189,6 +189,9 @@ namespace llvm {
       /// Direct move from a GPR to a VSX register (zero)
       MTVSRZ,
 
+      /// Direct move of 2 consective GPR to a VSX register.
+      BUILD_FP128,
+
       /// Extract a subvector from signed integer vector and convert to FP.
       /// It is primarily used to convert a (widened) illegal integer vector
       /// type to a legal floating point vector type.
@@ -1065,6 +1068,7 @@ namespace llvm {
 
     SDValue lowerEH_SJLJ_SETJMP(SDValue Op, SelectionDAG &DAG) const;
     SDValue lowerEH_SJLJ_LONGJMP(SDValue Op, SelectionDAG &DAG) const;
+    SDValue LowerBITCAST(SDValue Op, SelectionDAG &DAG) const;
 
     SDValue DAGCombineExtBoolTrunc(SDNode *N, DAGCombinerInfo &DCI) const;
     SDValue DAGCombineBuildVector(SDNode *N, DAGCombinerInfo &DCI) const;

llvm/lib/Target/PowerPC/PPCInstrInfo.td

@@ -218,6 +218,13 @@ def PPCsrl        : SDNode<"PPCISD::SRL"       , SDTIntShiftOp>;
 def PPCsra        : SDNode<"PPCISD::SRA"       , SDTIntShiftOp>;
 def PPCshl        : SDNode<"PPCISD::SHL"       , SDTIntShiftOp>;
 
+// Move 2 i64 values into a VSX register
+def PPCbuild_fp128: SDNode<"PPCISD::BUILD_FP128",
+                           SDTypeProfile<1, 2,
+                             [SDTCisFP<0>, SDTCisSameSizeAs<1,2>,
+                              SDTCisSameAs<1,2>]>,
+                           []>;
+
 // These are target-independent nodes, but have target-specific formats.
 def callseq_start : SDNode<"ISD::CALLSEQ_START", SDT_PPCCallSeqStart,
                            [SDNPHasChain, SDNPOutGlue]>;

llvm/lib/Target/PowerPC/PPCInstrVSX.td

@@ -3387,6 +3387,17 @@ let AddedComplexity = 400, Predicates = [HasP9Vector] in {
 
 } // end HasP9Vector, AddedComplexity
 
+let AddedComplexity = 400 in {
+  let Predicates = [IsISA3_0, HasP9Vector, HasDirectMove, IsBigEndian] in {
+    def : Pat<(f128 (PPCbuild_fp128 i64:$rB, i64:$rA)),
+              (f128 (COPY_TO_REGCLASS (MTVSRDD $rB, $rA), VRRC))>;
+  }
+  let Predicates = [IsISA3_0, HasP9Vector, HasDirectMove, IsLittleEndian] in {
+    def : Pat<(f128 (PPCbuild_fp128 i64:$rA, i64:$rB)),
+              (f128 (COPY_TO_REGCLASS (MTVSRDD $rB, $rA), VRRC))>;
+  }
+}
+
 let Predicates = [HasP9Vector] in {
   let isPseudo = 1 in {
     let mayStore = 1 in {