1 files changed, 23 insertions, 9 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d888676583f3..5ecc6da32144 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6198,13 +6198,27 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
       }
     }
 
-    // sext(setcc x, y, cc) -> (select (setcc x, y, cc), -1, 0)
-    unsigned ElementWidth = VT.getScalarType().getSizeInBits();
+    // sext(setcc x, y, cc) -> (select (setcc x, y, cc), T, 0)
+    // Here, T can be 1 or -1, depending on the type of the setcc and
+    // getBooleanContents().
+    unsigned SetCCWidth = N0.getValueType().getScalarSizeInBits();
+
     SDLoc DL(N);
-    SDValue NegOne =
-      DAG.getConstant(APInt::getAllOnesValue(ElementWidth), DL, VT);
+    // To determine the "true" side of the select, we need to know the high bit
+    // of the value returned by the setcc if it evaluates to true.
+    // If the type of the setcc is i1, then the true case of the select is just
+    // sext(i1 1), that is, -1.
+    // If the type of the setcc is larger (say, i8) then the value of the high
+    // bit depends on getBooleanContents(). So, ask TLI for a real "true" value
+    // of the appropriate width.
+    SDValue ExtTrueVal =
+        (SetCCWidth == 1)
+            ? DAG.getConstant(APInt::getAllOnesValue(VT.getScalarSizeInBits()),
+                              DL, VT)
+            : TLI.getConstTrueVal(DAG, VT, DL);
+
     if (SDValue SCC = SimplifySelectCC(
-            DL, N0.getOperand(0), N0.getOperand(1), NegOne,
+            DL, N0.getOperand(0), N0.getOperand(1), ExtTrueVal,
             DAG.getConstant(0, DL, VT),
             cast<CondCodeSDNode>(N0.getOperand(2))->get(), true))
       return SCC;
@@ -6215,10 +6229,10 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
           TLI.isOperationLegal(ISD::SETCC, N0.getOperand(0).getValueType())) {
         SDLoc DL(N);
         ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
-        SDValue SetCC = DAG.getSetCC(DL, SetCCVT,
-                                     N0.getOperand(0), N0.getOperand(1), CC);
-        return DAG.getSelect(DL, VT, SetCC,
-                             NegOne, DAG.getConstant(0, DL, VT));
+        SDValue SetCC =
+            DAG.getSetCC(DL, SetCCVT, N0.getOperand(0), N0.getOperand(1), CC);
+        return DAG.getSelect(DL, VT, SetCC, ExtTrueVal,
+                             DAG.getConstant(0, DL, VT));
       }
     }
   }