Have 'optnone' respect the -fast-isel=false option.

This is primarily useful for debugging optnone v. ISel issues.

Differential Revision: http://reviews.llvm.org/D14792

llvm-svn: 254335
diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index 5b8c825..da24cb1 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -125,9 +125,10 @@
   PM.add(new MachineFunctionAnalysis(*TM, MFInitializer));
 
   // Enable FastISel with -fast, but allow that to be overridden.
+  TM->setO0WantsFastISel(EnableFastISelOption != cl::BOU_FALSE);
   if (EnableFastISelOption == cl::BOU_TRUE ||
       (TM->getOptLevel() == CodeGenOpt::None &&
-       EnableFastISelOption != cl::BOU_FALSE))
+       TM->getO0WantsFastISel()))
     TM->setFastISel(true);
 
   // Ask the target for an isel.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index ebf071c..3bbe5d4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -264,13 +264,17 @@
         return;
       IS.OptLevel = NewOptLevel;
       IS.TM.setOptLevel(NewOptLevel);
-      SavedFastISel = IS.TM.Options.EnableFastISel;
-      if (NewOptLevel == CodeGenOpt::None)
-        IS.TM.setFastISel(true);
       DEBUG(dbgs() << "\nChanging optimization level for Function "
             << IS.MF->getFunction()->getName() << "\n");
       DEBUG(dbgs() << "\tBefore: -O" << SavedOptLevel
             << " ; After: -O" << NewOptLevel << "\n");
+      SavedFastISel = IS.TM.Options.EnableFastISel;
+      if (NewOptLevel == CodeGenOpt::None) {
+        IS.TM.setFastISel(IS.TM.getO0WantsFastISel());
+        DEBUG(dbgs() << "\tFastISel is "
+              << (IS.TM.Options.EnableFastISel ? "enabled" : "disabled")
+              << "\n");
+      }
     }
 
     ~OptLevelChanger() {