From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Thu, 28 Feb 2019 11:39:52 +0000 (+0000)
Subject: [X86][AVX] Remove superfluous insert_subvector(zero, bitcast(x)) -> bitcast(insert_su... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=dac99072241379dd01f8489930ccb1141acad1b4;p=llvm

[X86][AVX] Remove superfluous insert_subvector(zero, bitcast(x)) -> bitcast(insert_subvector(zero, x)) fold

This is caught by other existing bitcast folds.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355084 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 76f65782907..4c85267343a 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -41888,20 +41888,6 @@ static SDValue combineInsertSubvector(SDNode *N, SelectionDAG &DAG,
                            getZeroVector(OpVT, Subtarget, DAG, dl),
                            Ins.getOperand(1), N->getOperand(2));
     }
-
-    // If we're inserting a bitcast into zeros, rewrite the insert and move the
-    // bitcast to the other side. This helps with detecting zero extending
-    // during isel.
-    // TODO: Is this useful for other indices than 0?
-    if (!IsI1Vector && SubVec.getOpcode() == ISD::BITCAST && IdxVal == 0) {
-      MVT CastVT = SubVec.getOperand(0).getSimpleValueType();
-      unsigned NumElems = OpVT.getSizeInBits() / CastVT.getScalarSizeInBits();
-      MVT NewVT = MVT::getVectorVT(CastVT.getVectorElementType(), NumElems);
-      SDValue Insert = DAG.getNode(ISD::INSERT_SUBVECTOR, dl, NewVT,
-                                   DAG.getBitcast(NewVT, Vec),
-                                   SubVec.getOperand(0), N->getOperand(2));
-      return DAG.getBitcast(OpVT, Insert);
-    }
   }
 
   // Stop here if this is an i1 vector.