commit 9ae73cdbc1e59fd3149e60efd2b96e68e8d1669b
Author: David Green <david.green@arm.com>
Date:   Fri Jan 22 11:11:36 2021 +0000

    [ARM] Adjust isSaturatingConditional to return a new SDValue. NFC
    
    This replaces the isSaturatingConditional function with
    LowerSaturatingConditional that directly returns a new SSAT or
    USAT SDValue, instead of returning true and the components of it.

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index aabfad045d9f..949d2ffc1714 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -5036,17 +5036,13 @@ static bool isLowerSaturate(const SDValue LHS, const SDValue RHS,
 //     etc.
 //
 // LLVM canonicalizes these to either a min(max()) or a max(min())
-// pattern. This function tries to match one of these and will return true
-// if successful.
+// pattern. This function tries to match one of these and will return a SSAT
+// node if successful.
 //
-// USAT works similarily to SSAT but bounds on the interval [0, k] where k + 1 is
-// a power of 2.
-//
-// It returns true if the conversion can be done, false otherwise.
-// Additionally, the variable is returned in parameter V, the constant in K and
-// usat is set to true if the conditional represents an unsigned saturation
-static bool isSaturatingConditional(const SDValue &Op, SDValue &V,
-                                    uint64_t &K, bool &Usat) {
+// USAT works similarily to SSAT but bounds on the interval [0, k] where k + 1
+// is a power of 2.
+static SDValue LowerSaturatingConditional(SDValue Op, SelectionDAG &DAG) {
+  EVT VT = Op.getValueType();
   SDValue V1 = Op.getOperand(0);
   SDValue K1 = Op.getOperand(1);
   SDValue TrueVal1 = Op.getOperand(2);
@@ -5055,7 +5051,7 @@ static bool isSaturatingConditional(const SDValue &Op, SDValue &V,
 
   const SDValue Op2 = isa<ConstantSDNode>(TrueVal1) ? FalseVal1 : TrueVal1;
   if (Op2.getOpcode() != ISD::SELECT_CC)
-    return false;
+    return SDValue();
 
   SDValue V2 = Op2.getOperand(0);
   SDValue K2 = Op2.getOperand(1);
@@ -5074,41 +5070,39 @@ static bool isSaturatingConditional(const SDValue &Op, SDValue &V,
 
   // Check that the registers and the constants match a max(min()) or min(max())
   // pattern
-  if (V1Tmp == TrueVal1 && V2Tmp == TrueVal2 && K1 == FalseVal1 &&
-      K2 == FalseVal2 &&
-      ((isGTorGE(CC1) && isLTorLE(CC2)) || (isLTorLE(CC1) && isGTorGE(CC2)))) {
-
-    // Check that the constant in the lower-bound check is
-    // the opposite of the constant in the upper-bound check
-    // in 1's complement.
-    if (!isa<ConstantSDNode>(K1) || !isa<ConstantSDNode>(K2))
-      return false;
+  if (V1Tmp != TrueVal1 || V2Tmp != TrueVal2 || K1 != FalseVal1 ||
+      K2 != FalseVal2 ||
+      !((isGTorGE(CC1) && isLTorLE(CC2)) || (isLTorLE(CC1) && isGTorGE(CC2))))
+    return SDValue();
 
-    int64_t Val1 = cast<ConstantSDNode>(K1)->getSExtValue();
-    int64_t Val2 = cast<ConstantSDNode>(K2)->getSExtValue();
-    int64_t PosVal = std::max(Val1, Val2);
-    int64_t NegVal = std::min(Val1, Val2);
+  // Check that the constant in the lower-bound check is
+  // the opposite of the constant in the upper-bound check
+  // in 1's complement.
+  if (!isa<ConstantSDNode>(K1) || !isa<ConstantSDNode>(K2))
+    return SDValue();
 
-    if (!((Val1 > Val2 && isLTorLE(CC1)) || (Val1 < Val2 && isLTorLE(CC2))) ||
-        !isPowerOf2_64(PosVal + 1)) 
-      return false;
+  int64_t Val1 = cast<ConstantSDNode>(K1)->getSExtValue();
+  int64_t Val2 = cast<ConstantSDNode>(K2)->getSExtValue();
+  int64_t PosVal = std::max(Val1, Val2);
+  int64_t NegVal = std::min(Val1, Val2);
 
-    // Handle the difference between USAT (unsigned) and SSAT (signed)
-    // saturation
-    if (Val1 == ~Val2)
-      Usat = false;
-    else if (NegVal == 0)
-      Usat = true;
-    else
-      return false;
+  if (!((Val1 > Val2 && isLTorLE(CC1)) || (Val1 < Val2 && isLTorLE(CC2))) ||
+      !isPowerOf2_64(PosVal + 1))
+    return SDValue();
 
-    V = V2Tmp;
-    // At this point, PosVal is guaranteed to be positive
-    K = (uint64_t) PosVal; 
+  // Handle the difference between USAT (unsigned) and SSAT (signed)
+  // saturation
+  // At this point, PosVal is guaranteed to be positive
+  uint64_t K = PosVal;
+  SDLoc dl(Op);
+  if (Val1 == ~Val2)
+    return DAG.getNode(ARMISD::SSAT, dl, VT, V2Tmp,
+                       DAG.getConstant(countTrailingOnes(K), dl, VT));
+  if (NegVal == 0)
+    return DAG.getNode(ARMISD::USAT, dl, VT, V2Tmp,
+                       DAG.getConstant(countTrailingOnes(K), dl, VT));
 
-    return true;
-  }
-  return false;
+  return SDValue();
 }
 
 // Check if a condition of the type x < k ? k : x can be converted into a
@@ -5168,18 +5162,9 @@ SDValue ARMTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   SDLoc dl(Op);
 
   // Try to convert two saturating conditional selects into a single SSAT
-  SDValue SatValue;
-  uint64_t SatConstant;
-  bool SatUSat;
-  if (((!Subtarget->isThumb() && Subtarget->hasV6Ops()) || Subtarget->isThumb2()) &&
-      isSaturatingConditional(Op, SatValue, SatConstant, SatUSat)) {
-    if (SatUSat)
-      return DAG.getNode(ARMISD::USAT, dl, VT, SatValue,
-                         DAG.getConstant(countTrailingOnes(SatConstant), dl, VT));
-    else
-      return DAG.getNode(ARMISD::SSAT, dl, VT, SatValue,
-                         DAG.getConstant(countTrailingOnes(SatConstant), dl, VT));
-  }
+  if ((!Subtarget->isThumb() && Subtarget->hasV6Ops()) || Subtarget->isThumb2())
+    if (SDValue SatValue = LowerSaturatingConditional(Op, DAG))
+      return SatValue;
 
   // Try to convert expressions of the form x < k ? k : x (and similar forms)
   // into more efficient bit operations, which is possible when k is 0 or -1
@@ -5188,6 +5173,7 @@ SDValue ARMTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   // instructions.
   // Only allow this transformation on full-width (32-bit) operations
   SDValue LowerSatConstant;
+  SDValue SatValue;
   if (VT == MVT::i32 &&
       isLowerSaturatingConditional(Op, SatValue, LowerSatConstant)) {
     SDValue ShiftV = DAG.getNode(ISD::SRA, dl, VT, SatValue,