Revert [X86] SimplifyDemandedVectorElts - attempt to recombine target shuffle using DemandedElts mask (reapplied)

This reverts r368662 (git commit 1a8d790cf5f89c1df718844f13e934e39bef6ef5)

The compile-time regression repro is in https://bugs.llvm.org/show_bug.cgi?id=43024

llvm-svn: 369167

1 files changed, 0 insertions, 17 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index c9e3390c5d1..207782bc80b 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33905,23 +33905,6 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       return true;
   }
 
-  // If we don't demand all elements, then attempt to combine to a simpler
-  // shuffle.
-  // TODO: Handle other depths, but first we need to handle the fact that
-  // it might combine to the same shuffle.
-  if (!DemandedElts.isAllOnesValue() && Depth == 0) {
-    SmallVector<int, 32> DemandedMask(NumElts, SM_SentinelUndef);
-    for (int i = 0; i != NumElts; ++i)
-      if (DemandedElts[i])
-        DemandedMask[i] = i;
-
-    SDValue NewShuffle = combineX86ShufflesRecursively(
-        {Op}, 0, Op, DemandedMask, {}, Depth, /*HasVarMask*/ false,
-        /*AllowVarMask*/ true, TLO.DAG, Subtarget);
-    if (NewShuffle)
-      return TLO.CombineTo(Op, NewShuffle);
-  }
-
   // Extract known zero/undef elements.
   // TODO - Propagate input undef/zero elts.
   for (int i = 0; i != NumElts; ++i) {