From 393b4bd1362f6634a972157e7c2f3936f51f7356 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sat, 27 Jun 2020 19:10:13 +0100
Subject: [PATCH] [X86] SimplifyDemandedVectorEltsForTargetNode - merge
 shuffle/pack lower demanded elements handling.

Generalize the vector operand extraction code for shuffle/pack ops - we can assume that the vector operands are the same width as the result, and any non-vector values can be reused directly in the smaller width op.
---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 77 +++++++------------------
 1 file changed, 20 insertions(+), 57 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index fd69791b80e8..bef29f0948cb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -37053,18 +37053,6 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       ExtSizeInBits = SizeInBits / 4;
 
     switch (Opc) {
-      // Zero upper elements.
-    case X86ISD::VZEXT_MOVL: {
-      SDLoc DL(Op);
-      SDValue Ext0 =
-          extractSubVector(Op.getOperand(0), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue ExtOp =
-          TLO.DAG.getNode(Opc, DL, Ext0.getValueType(), Ext0);
-      SDValue UndefVec = TLO.DAG.getUNDEF(VT);
-      SDValue Insert =
-          insertSubVector(UndefVec, ExtOp, 0, TLO.DAG, DL, ExtSizeInBits);
-      return TLO.CombineTo(Op, Insert);
-    }
       // Subvector broadcast.
     case X86ISD::SUBV_BROADCAST: {
       SDLoc DL(Op);
@@ -37080,11 +37068,6 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       return TLO.CombineTo(Op, insertSubVector(TLO.DAG.getUNDEF(VT), Src, 0,
                                                TLO.DAG, DL, ExtSizeInBits));
     }
-      // Target unary shuffles by immediate:
-    case X86ISD::PSHUFD:
-    case X86ISD::PSHUFLW:
-    case X86ISD::PSHUFHW:
-    case X86ISD::VPERMILPI:
       // Byte shifts by immediate.
     case X86ISD::VSHLDQ:
     case X86ISD::VSRLDQ:
@@ -37122,11 +37105,20 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       }
       break;
     }
+      // Zero upper elements.
+    case X86ISD::VZEXT_MOVL:
+      // Target unary shuffles by immediate:
+    case X86ISD::PSHUFD:
+    case X86ISD::PSHUFLW:
+    case X86ISD::PSHUFHW:
+    case X86ISD::VPERMILPI:
       // (Non-Lane Crossing) Target Shuffles.
     case X86ISD::VPERMILPV:
+    case X86ISD::VPERMIL2:
     case X86ISD::PSHUFB:
     case X86ISD::UNPCKL:
     case X86ISD::UNPCKH:
+    case X86ISD::BLENDI:
       // Saturated Packs.
     case X86ISD::PACKSS:
     case X86ISD::PACKUS:
@@ -37136,49 +37128,20 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
     case X86ISD::FHADD:
     case X86ISD::FHSUB: {
       SDLoc DL(Op);
+      SmallVector<SDValue, 4> Ops;
+      for (unsigned i = 0, e = Op.getNumOperands(); i != e; ++i) {
+        SDValue SrcOp = Op.getOperand(i);
+        EVT SrcVT = SrcOp.getValueType();
+        assert((!SrcVT.isVector() || SrcVT.getSizeInBits() == SizeInBits) &&
+               "Unsupported vector size");
+        Ops.push_back(SrcVT.isVector() ? extractSubVector(SrcOp, 0, TLO.DAG, DL,
+                                                          ExtSizeInBits)
+                                       : SrcOp);
+      }
       MVT ExtVT = VT.getSimpleVT();
       ExtVT = MVT::getVectorVT(ExtVT.getScalarType(),
                                ExtSizeInBits / ExtVT.getScalarSizeInBits());
-      SDValue Ext0 =
-          extractSubVector(Op.getOperand(0), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue Ext1 =
-          extractSubVector(Op.getOperand(1), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue ExtOp = TLO.DAG.getNode(Opc, DL, ExtVT, Ext0, Ext1);
-      SDValue UndefVec = TLO.DAG.getUNDEF(VT);
-      SDValue Insert =
-          insertSubVector(UndefVec, ExtOp, 0, TLO.DAG, DL, ExtSizeInBits);
-      return TLO.CombineTo(Op, Insert);
-    }
-      // Vector blend by immediate.
-    case X86ISD::BLENDI: {
-      SDLoc DL(Op);
-      MVT ExtVT = VT.getSimpleVT();
-      ExtVT = MVT::getVectorVT(ExtVT.getScalarType(),
-                               ExtSizeInBits / ExtVT.getScalarSizeInBits());
-      SDValue Ext0 =
-          extractSubVector(Op.getOperand(0), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue Ext1 =
-          extractSubVector(Op.getOperand(1), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue ExtOp =
-          TLO.DAG.getNode(Opc, DL, ExtVT, Ext0, Ext1, Op.getOperand(2));
-      SDValue UndefVec = TLO.DAG.getUNDEF(VT);
-      SDValue Insert =
-          insertSubVector(UndefVec, ExtOp, 0, TLO.DAG, DL, ExtSizeInBits);
-      return TLO.CombineTo(Op, Insert);
-    }
-    case X86ISD::VPERMIL2: {
-      SDLoc DL(Op);
-      MVT ExtVT = VT.getSimpleVT();
-      ExtVT = MVT::getVectorVT(ExtVT.getScalarType(),
-                               ExtSizeInBits / ExtVT.getScalarSizeInBits());
-      SDValue Ext0 =
-          extractSubVector(Op.getOperand(0), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue Ext1 =
-          extractSubVector(Op.getOperand(1), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue Ext2 =
-          extractSubVector(Op.getOperand(2), 0, TLO.DAG, DL, ExtSizeInBits);
-      SDValue ExtOp =
-          TLO.DAG.getNode(Opc, DL, ExtVT, Ext0, Ext1, Ext2, Op.getOperand(3));
+      SDValue ExtOp = TLO.DAG.getNode(Opc, DL, ExtVT, Ops);
       SDValue UndefVec = TLO.DAG.getUNDEF(VT);
       SDValue Insert =
           insertSubVector(UndefVec, ExtOp, 0, TLO.DAG, DL, ExtSizeInBits);