From: Sanjay Patel <spatel@rotateright.com>
Date: Mon, 28 Nov 2016 21:47:41 +0000 (+0000)
Subject: [DAG] add helper function for selectcc --> and+shift transforms; NFC
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2365a7c201d773c001777fbd5b67b60e4d8ab72b;p=llvm

[DAG] add helper function for selectcc --> and+shift transforms; NFC


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288073 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 09989b84083..c301491f53b 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -341,6 +341,8 @@ namespace {
     SDValue SimplifySelectCC(const SDLoc &DL, SDValue N0, SDValue N1,
                              SDValue N2, SDValue N3, ISD::CondCode CC,
                              bool NotExtCompare = false);
+    SDValue foldSelectCCToShiftAnd(const SDLoc &DL, SDValue N0, SDValue N1,
+                                   SDValue N2, SDValue N3, ISD::CondCode CC);
     SDValue SimplifySetCC(EVT VT, SDValue N0, SDValue N1, ISD::CondCode Cond,
                           const SDLoc &DL, bool foldBooleans = true);
 
@@ -14564,6 +14566,53 @@ bool DAGCombiner::SimplifySelectOps(SDNode *TheSelect, SDValue LHS,
   return false;
 }
 
+SDValue DAGCombiner::foldSelectCCToShiftAnd(const SDLoc &DL, SDValue N0,
+                                            SDValue N1, SDValue N2, SDValue N3,
+                                            ISD::CondCode CC) {
+  // Check to see if we can perform the "gzip trick", transforming
+  // (select_cc setlt X, 0, A, 0) -> (and (sra X, (sub size(X), 1), A)
+  if (isNullConstant(N3) && CC == ISD::SETLT &&
+      (isNullConstant(N1) ||               // (a < 0) ? b : 0
+       (isOneConstant(N1) && N0 == N2))) { // (a < 1) ? a : 0
+    EVT XType = N0.getValueType();
+    EVT AType = N2.getValueType();
+    if (XType.bitsGE(AType)) {
+      // and (sra X, size(X)-1, A) -> "and (srl X, C2), A" iff A is a
+      // single-bit constant.
+      auto *N2C = dyn_cast<ConstantSDNode>(N2.getNode());
+      if (N2C && ((N2C->getAPIntValue() & (N2C->getAPIntValue() - 1)) == 0)) {
+        unsigned ShCtV = N2C->getAPIntValue().logBase2();
+        ShCtV = XType.getSizeInBits() - ShCtV - 1;
+        SDValue ShCt = DAG.getConstant(ShCtV, SDLoc(N0),
+                                       getShiftAmountTy(N0.getValueType()));
+        SDValue Shift = DAG.getNode(ISD::SRL, SDLoc(N0), XType, N0, ShCt);
+        AddToWorklist(Shift.getNode());
+
+        if (XType.bitsGT(AType)) {
+          Shift = DAG.getNode(ISD::TRUNCATE, DL, AType, Shift);
+          AddToWorklist(Shift.getNode());
+        }
+
+        return DAG.getNode(ISD::AND, DL, AType, Shift, N2);
+      }
+
+      SDValue Shift =
+          DAG.getNode(ISD::SRA, SDLoc(N0), XType, N0,
+                      DAG.getConstant(XType.getSizeInBits() - 1, SDLoc(N0),
+                                      getShiftAmountTy(N0.getValueType())));
+      AddToWorklist(Shift.getNode());
+
+      if (XType.bitsGT(AType)) {
+        Shift = DAG.getNode(ISD::TRUNCATE, DL, AType, Shift);
+        AddToWorklist(Shift.getNode());
+      }
+
+      return DAG.getNode(ISD::AND, DL, AType, Shift, N2);
+    }
+  }
+  return SDValue();
+}
+
 /// Simplify an expression of the form (N0 cond N1) ? N2 : N3
 /// where 'cond' is the comparison specified by CC.
 SDValue DAGCombiner::SimplifySelectCC(const SDLoc &DL, SDValue N0, SDValue N1,
@@ -14660,48 +14709,8 @@ SDValue DAGCombiner::SimplifySelectCC(const SDLoc &DL, SDValue N0, SDValue N1,
       }
     }
 
-  // Check to see if we can perform the "gzip trick", transforming
-  // (select_cc setlt X, 0, A, 0) -> (and (sra X, (sub size(X), 1), A)
-  if (isNullConstant(N3) && CC == ISD::SETLT &&
-      (isNullConstant(N1) ||                 // (a < 0) ? b : 0
-       (isOneConstant(N1) && N0 == N2))) {   // (a < 1) ? a : 0
-    EVT XType = N0.getValueType();
-    EVT AType = N2.getValueType();
-    if (XType.bitsGE(AType)) {
-      // and (sra X, size(X)-1, A) -> "and (srl X, C2), A" iff A is a
-      // single-bit constant.
-      if (N2C && ((N2C->getAPIntValue() & (N2C->getAPIntValue() - 1)) == 0)) {
-        unsigned ShCtV = N2C->getAPIntValue().logBase2();
-        ShCtV = XType.getSizeInBits() - ShCtV - 1;
-        SDValue ShCt = DAG.getConstant(ShCtV, SDLoc(N0),
-                                       getShiftAmountTy(N0.getValueType()));
-        SDValue Shift = DAG.getNode(ISD::SRL, SDLoc(N0),
-                                    XType, N0, ShCt);
-        AddToWorklist(Shift.getNode());
-
-        if (XType.bitsGT(AType)) {
-          Shift = DAG.getNode(ISD::TRUNCATE, DL, AType, Shift);
-          AddToWorklist(Shift.getNode());
-        }
-
-        return DAG.getNode(ISD::AND, DL, AType, Shift, N2);
-      }
-
-      SDValue Shift = DAG.getNode(ISD::SRA, SDLoc(N0),
-                                  XType, N0,
-                                  DAG.getConstant(XType.getSizeInBits() - 1,
-                                                  SDLoc(N0),
-                                         getShiftAmountTy(N0.getValueType())));
-      AddToWorklist(Shift.getNode());
-
-      if (XType.bitsGT(AType)) {
-        Shift = DAG.getNode(ISD::TRUNCATE, DL, AType, Shift);
-        AddToWorklist(Shift.getNode());
-      }
-
-      return DAG.getNode(ISD::AND, DL, AType, Shift, N2);
-    }
-  }
+  if (SDValue V = foldSelectCCToShiftAnd(DL, N0, N1, N2, N3, CC))
+    return V;
 
   // fold (select_cc seteq (and x, y), 0, 0, A) -> (and (shr (shl x)) A)
   // where y is has a single bit set.