[x86] Refactor a PowerPC specific ctlz/srl transformation (NFC).

Following the discussion on D22038, this refactors a PowerPC specific setcc -> srl(ctlz) transformation so it can be used by other targets.

Differential Revision: https://reviews.llvm.org/D23445

llvm-svn: 278799

2 files changed, 7 insertions, 13 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 2e1df661b4f..e2cc9212597 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2362,20 +2362,10 @@ SDValue PPCTargetLowering::LowerSETCC(SDValue Op, SelectionDAG &DAG) const {
   // If we're comparing for equality to zero, expose the fact that this is
   // implemented as a ctlz/srl pair on ppc, so that the dag combiner can
   // fold the new nodes.
+  if (SDValue V = lowerCmpEqZeroToCtlzSrl(Op, DAG))
+    return V;
+
   if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
-    if (C->isNullValue() && CC == ISD::SETEQ) {
-      EVT VT = Op.getOperand(0).getValueType();
-      SDValue Zext = Op.getOperand(0);
-      if (VT.bitsLT(MVT::i32)) {
-        VT = MVT::i32;
-        Zext = DAG.getNode(ISD::ZERO_EXTEND, dl, VT, Op.getOperand(0));
-      }
-      unsigned Log2b = Log2_32(VT.getSizeInBits());
-      SDValue Clz = DAG.getNode(ISD::CTLZ, dl, VT, Zext);
-      SDValue Scc = DAG.getNode(ISD::SRL, dl, VT, Clz,
-                                DAG.getConstant(Log2b, dl, MVT::i32));
-      return DAG.getNode(ISD::TRUNCATE, dl, MVT::i32, Scc);
-    }
     // Leave comparisons against 0 and -1 alone for now, since they're usually
     // optimized.  FIXME: revisit this when we can custom lower all setcc
     // optimizations.
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index c12f9c664c9..13b8637fef6 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -492,6 +492,10 @@ namespace llvm {
       return true;
     }
 
+    bool isCtlzFast() const override {
+      return true;
+    }
+
     bool supportSplitCSR(MachineFunction *MF) const override {
       return
         MF->getFunction()->getCallingConv() == CallingConv::CXX_FAST_TLS &&