[x86] add materializeVectorConstant() helper function; NFC

LowerBUILD_VECTOR is still over 300 lines long, but it's a start...

llvm-svn: 258858

1 files changed, 29 insertions, 15 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cefc0a7c75a..cb5a8b3d2df 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6389,39 +6389,53 @@ static SDValue LowerToHorizontalOp(const BuildVectorSDNode *BV,
   return SDValue();
 }
 
-SDValue
-X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
-  SDLoc dl(Op);
-
+/// Create a vector constant without a load. SSE/AVX provide the bare minimum
+/// functionality to do this, so it's all zeros, all ones, or some derivation
+/// that is cheap to calculate.
+static SDValue materializeVectorConstant(SDValue Op, SelectionDAG &DAG,
+                                         const X86Subtarget &Subtarget) {
+  SDLoc DL(Op);
   MVT VT = Op.getSimpleValueType();
-  MVT ExtVT = VT.getVectorElementType();
-  unsigned NumElems = Op.getNumOperands();
 
-  // Generate vectors for predicate vectors.
-  if (VT.getVectorElementType() == MVT::i1 && Subtarget->hasAVX512())
-    return LowerBUILD_VECTORvXi1(Op, DAG);
-
-  // Vectors containing all zeros can be matched by pxor and xorps later
+  // Vectors containing all zeros can be matched by pxor and xorps.
   if (ISD::isBuildVectorAllZeros(Op.getNode())) {
     // Canonicalize this to <4 x i32> to 1) ensure the zero vectors are CSE'd
     // and 2) ensure that i64 scalars are eliminated on x86-32 hosts.
     if (VT == MVT::v4i32 || VT == MVT::v8i32 || VT == MVT::v16i32)
       return Op;
 
-    return getZeroVector(VT, Subtarget, DAG, dl);
+    return getZeroVector(VT, &Subtarget, DAG, DL);
   }
 
   // Vectors containing all ones can be matched by pcmpeqd on 128-bit width
   // vectors or broken into v4i32 operations on 256-bit vectors. AVX2 can use
   // vpcmpeqd on 256-bit vectors.
-  if (Subtarget->hasSSE2() && ISD::isBuildVectorAllOnes(Op.getNode())) {
-    if (VT == MVT::v4i32 || (VT == MVT::v8i32 && Subtarget->hasInt256()))
+  if (Subtarget.hasSSE2() && ISD::isBuildVectorAllOnes(Op.getNode())) {
+    if (VT == MVT::v4i32 || (VT == MVT::v8i32 && Subtarget.hasInt256()))
       return Op;
 
     if (!VT.is512BitVector())
-      return getOnesVector(VT, Subtarget, DAG, dl);
+      return getOnesVector(VT, &Subtarget, DAG, DL);
   }
 
+  return SDValue();
+}
+
+SDValue
+X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
+  SDLoc dl(Op);
+
+  MVT VT = Op.getSimpleValueType();
+  MVT ExtVT = VT.getVectorElementType();
+  unsigned NumElems = Op.getNumOperands();
+
+  // Generate vectors for predicate vectors.
+  if (VT.getVectorElementType() == MVT::i1 && Subtarget->hasAVX512())
+    return LowerBUILD_VECTORvXi1(Op, DAG);
+
+  if (SDValue VectorConstant = materializeVectorConstant(Op, DAG, *Subtarget))
+    return VectorConstant;
+
   BuildVectorSDNode *BV = cast<BuildVectorSDNode>(Op.getNode());
   if (SDValue AddSub = LowerToAddSub(BV, Subtarget, DAG))
     return AddSub;