Remove check for single use in ShrinkDemandedConstant

This removes check for single use from general ShrinkDemandedConstant
to the BE because of the AArch64 regression after D56289/rL350475.

After several hours of experiments I did not come up with a testcase
failing on any other targets if check is not performed.

Moreover, direct call to ShrinkDemandedConstant is not really needed
and superceed by SimplifyDemandedBits.

Differential Revision: https://reviews.llvm.org/D56406

llvm-svn: 350684
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 894806b..0e2e3b0 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -8586,8 +8586,7 @@
   TargetLowering::TargetLoweringOpt TLO(DAG, !DCI.isBeforeLegalize(),
                                         !DCI.isBeforeLegalizeOps());
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
-  if (TLI.ShrinkDemandedConstant(Src, Demanded, TLO) ||
-      TLI.SimplifyDemandedBits(Src, Demanded, Known, TLO)) {
+  if (TLI.SimplifyDemandedBits(Src, Demanded, Known, TLO)) {
     DCI.CommitTargetLoweringOpt(TLO);
   }