Branch folding may invalidate liveness.
Branch folding can use a register scavenger to update liveness
information when required. Don't do that if liveness information is
already invalid.
llvm-svn: 153517
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index f57f4a8..ef1d2ba 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -23,6 +23,7 @@
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
@@ -183,8 +184,14 @@
TII = tii;
TRI = tri;
MMI = mmi;
+ RS = NULL;
- RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : NULL;
+ // Use a RegScavenger to help update liveness when required.
+ MachineRegisterInfo &MRI = MF.getRegInfo();
+ if (MRI.tracksLiveness() && TRI->requiresRegisterScavenging(MF))
+ RS = new RegScavenger();
+ else
+ MRI.invalidateLiveness();
// Fix CFG. The later algorithms expect it to be right.
bool MadeChange = false;