From eae7090e1c02785e81be0ea2ec562875ae43a907 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sat, 3 Oct 2015 16:26:52 +0000
Subject: [PATCH] [DAGCombiner] Merge SIGN_EXTEND_INREG vector constant folding
 methods. NCI.

visitSIGN_EXTEND_INREG calls SelectionDAG::getNode to constant fold scalar constants but handles vector constants itself, despite getNode being capable of dealing with them.

This required a minor change to the getNode implementation to actually deal with cases where the scalars of a BUILD_VECTOR were wider integers than the vector type - which was the only extra ability of the visitSIGN_EXTEND_INREG implementation.

No codegen intended and all existing tests remain the same.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249236 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/DAGCombiner.cpp  | 28 ++++------------------------
 lib/CodeGen/SelectionDAG/SelectionDAG.cpp |  4 ++--
 2 files changed, 6 insertions(+), 26 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ec64210667e..4c6983cb3aa 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6791,8 +6791,11 @@ SDValue DAGCombiner::visitSIGN_EXTEND_INREG(SDNode *N) {
   unsigned VTBits = VT.getScalarType().getSizeInBits();
   unsigned EVTBits = EVT.getScalarType().getSizeInBits();
 
+  if (N0.isUndef())
+    return DAG.getUNDEF(VT);
+
   // fold (sext_in_reg c1) -> c1
-  if (isa<ConstantSDNode>(N0) || N0.getOpcode() == ISD::UNDEF)
+  if (isConstantIntBuildVectorOrConstantInt(N0))
     return DAG.getNode(ISD::SIGN_EXTEND_INREG, SDLoc(N), VT, N0, N1);
 
   // If the input is already sign extended, just drop the extension.
@@ -6885,29 +6888,6 @@ SDValue DAGCombiner::visitSIGN_EXTEND_INREG(SDNode *N) {
                          BSwap, N1);
   }
 
-  // Fold a sext_inreg of a build_vector of ConstantSDNodes or undefs
-  // into a build_vector.
-  if (ISD::isBuildVectorOfConstantSDNodes(N0.getNode())) {
-    SmallVector<SDValue, 8> Elts;
-    unsigned NumElts = N0->getNumOperands();
-    unsigned ShAmt = VTBits - EVTBits;
-
-    for (unsigned i = 0; i != NumElts; ++i) {
-      SDValue Op = N0->getOperand(i);
-      if (Op->getOpcode() == ISD::UNDEF) {
-        Elts.push_back(Op);
-        continue;
-      }
-
-      ConstantSDNode *CurrentND = cast<ConstantSDNode>(Op);
-      const APInt &C = APInt(VTBits, CurrentND->getAPIntValue().getZExtValue());
-      Elts.push_back(DAG.getConstant(C.shl(ShAmt).ashr(ShAmt).getZExtValue(),
-                                     SDLoc(Op), Op.getValueType()));
-    }
-
-    return DAG.getNode(ISD::BUILD_VECTOR, SDLoc(N), VT, Elts);
-  }
-
   return SDValue();
 }
 
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index a968e965a0d..7e02d3ab1fc 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3576,13 +3576,13 @@ SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1,
       SmallVector<SDValue, 8> Ops;
       for (int i = 0, e = VT.getVectorNumElements(); i != e; ++i) {
         SDValue Op = N1.getOperand(i);
-        if (Op.getValueType() != VT.getScalarType()) break;
         if (Op.getOpcode() == ISD::UNDEF) {
-          Ops.push_back(Op);
+          Ops.push_back(getUNDEF(VT.getScalarType()));
           continue;
         }
         if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
           APInt Val = C->getAPIntValue();
+          Val = Val.zextOrTrunc(VT.getScalarSizeInBits());
           Ops.push_back(SignExtendInReg(Val));
           continue;
         }
-- 
2.11.0