X86: Fix the (saddo/ssub x, 1) -> incl/decl selection to check the right operand for 1.

Found by inspection.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127247 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 511cd31..2eb9841 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -8834,8 +8834,8 @@
   case ISD::SADDO:
     // A subtract of one will be selected as a INC. Note that INC doesn't
     // set CF, so we can't do this for UADDO.
-    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op))
-      if (C->getAPIntValue() == 1) {
+    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS))
+      if (C->isOne()) {
         BaseOp = X86ISD::INC;
         Cond = X86::COND_O;
         break;
@@ -8850,8 +8850,8 @@
   case ISD::SSUBO:
     // A subtract of one will be selected as a DEC. Note that DEC doesn't
     // set CF, so we can't do this for USUBO.
-    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op))
-      if (C->getAPIntValue() == 1) {
+    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS))
+      if (C->isOne()) {
         BaseOp = X86ISD::DEC;
         Cond = X86::COND_O;
         break;