Added TargetPassConfig::disablePass/substitutePass as a general mechanism to override specific passes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150562 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PTX/PTXTargetMachine.cpp b/lib/Target/PTX/PTXTargetMachine.cpp
index 056bc07..61285b1 100644
--- a/lib/Target/PTX/PTXTargetMachine.cpp
+++ b/lib/Target/PTX/PTXTargetMachine.cpp
@@ -151,11 +151,11 @@
 
 /// Add passes that optimize machine instructions after register allocation.
 void PTXPassConfig::addMachineLateOptimization() {
-  addPass(BranchFolderPassID);
-  printNoVerify("After BranchFolding");
+  if (addPass(BranchFolderPassID) != &NoPassID)
+    printNoVerify("After BranchFolding");
 
-  addPass(TailDuplicateID);
-  printNoVerify("After TailDuplicate");
+  if (addPass(TailDuplicateID) != &NoPassID)
+    printNoVerify("After TailDuplicate");
 }
 
 bool PTXPassConfig::addPreEmitPass() {