[PowerPC] Add a flag for experimenting with subreg liveness tracking

This cannot yet be enabled by default, it causes ~50 miscompiles in the test
suite.

llvm-svn: 225497

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index fb47c910c2f..d8ba1c71a0f 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -19,6 +19,7 @@
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetMachine.h"
@@ -32,6 +33,9 @@ using namespace llvm;
 #define GET_SUBTARGETINFO_CTOR
 #include "PPCGenSubtargetInfo.inc"
 
+static cl::opt<bool> UseSubRegLiveness("ppc-track-subreg-liveness",
+cl::desc("Enable subregister liveness tracking for PPC"), cl::Hidden);
+
 /// Return the datalayout string of a subtarget.
 static std::string getDataLayoutString(const Triple &T) {
   bool is64Bit = T.getArch() == Triple::ppc64 || T.getArch() == Triple::ppc64le;
@@ -234,3 +238,7 @@ bool PPCSubtarget::useAA() const {
   return needsAggressiveScheduling(DarwinDirective);
 }
 
+bool PPCSubtarget::enableSubRegLiveness() const {
+  return UseSubRegLiveness;
+}
+