[SystemZ] Fold AHIMux in foldMemoryOperandImpl.

AHIMux can be folded the same way as AHI.

Review: Ulrich Weigand
llvm-svn: 332703

Author: JonPsson

llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp

@@ -1509,7 +1509,13 @@ void SystemZDAGToDAGISel::Select(SDNode *Node) {
       CCMask = CurDAG->getConstant(ConstCCValid ^ ConstCCMask, SDLoc(Node),
                                    CCMask.getValueType());
       SDValue Op4 = Node->getOperand(4);
-      Node = CurDAG->UpdateNodeOperands(Node, Op1, Op0, CCValid, CCMask, Op4);
+      SDNode *UpdatedNode =
+        CurDAG->UpdateNodeOperands(Node, Op1, Op0, CCValid, CCMask, Op4);
+      if (UpdatedNode != Node) {
+        // In case this node already exists, replace Node with it.
+        ReplaceNode(Node, UpdatedNode);
+        Node = UpdatedNode;
+      }
     }
     break;
   }

llvm/test/CodeGen/SystemZ/selectcc-04.ll

@@ -0,0 +1,38 @@
+; This function contains two selects which differ only by having reversed
+; operand order. They are in fact equivalent, since the icmps that preceede
+; them also are the same except for reversed conditions. SelectionDAG will
+; discover this and return the other SELECT_CCMASK when the operands are
+; canonicalized. This must be handled by SystemZDAGToDAGISel::Select, or
+; instruction selection will fail.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13
+
+
+@g_1531 = external global [7 x i64], align 8
+@g_277 = external global <{ i64, i8, i8, i8, i8, i8, i8 }>, align 8
+@g_62.6 = external global i32, align 4
+
+define dso_local void @fun() {
+entry:
+  %tmp = add nuw nsw i16 0, 238
+  %tmp4 = sub nsw i16 %tmp, 0
+  store i64 4, i64* getelementptr inbounds (<{ i64, i8, i8, i8, i8, i8, i8 }>, <{ i64, i8, i8, i8, i8, i8, i8 }>* @g_277, i64 0, i32 0), align 8
+  %tmp5 = load i64, i64* getelementptr inbounds ([7 x i64], [7 x i64]* @g_1531, i64 0, i64 5), align 8
+  %tmp6 = trunc i64 %tmp5 to i32
+  %tmp7 = trunc i64 %tmp5 to i16
+  %tmp8 = shl i32 %tmp6, 24
+  %tmp9 = ashr exact i32 %tmp8, 24
+  %tmp10 = urem i16 %tmp7, %tmp4
+  %tmp11 = icmp eq i16 %tmp10, 0
+  %tmp12 = select i1 %tmp11, i32 0, i32 %tmp9
+  %tmp13 = icmp sge i32 %tmp12, undef
+  %tmp14 = zext i1 %tmp13 to i32
+  %tmp15 = or i32 0, %tmp14
+  %tmp16 = icmp ne i16 %tmp10, 0
+  %tmp17 = select i1 %tmp16, i32 %tmp9, i32 0
+  %tmp18 = icmp sge i32 %tmp17, undef
+  %tmp19 = zext i1 %tmp18 to i32
+  %tmp20 = or i32 %tmp15, %tmp19
+  store i32 %tmp20, i32* @g_62.6, align 4
+  unreachable
+}