Add an option to enable StrongPHIElimination, for ease of testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57259 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetOptions.h

@@ -103,6 +103,10 @@ namespace llvm {
   /// compile time.
   extern bool EnableFastISel;
   
+  /// StrongPHIElim - This flag enables more aggressive PHI elimination
+  /// wth earlier copy coalescing.
+  extern bool StrongPHIElim;
+
 } // End llvm namespace
 
 #endif

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -30,6 +30,7 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/Statistic.h"
@@ -67,8 +68,12 @@ void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<LiveVariables>();
   AU.addPreservedID(MachineLoopInfoID);
   AU.addPreservedID(MachineDominatorsID);
+  
+  if (!StrongPHIElim) {
     AU.addPreservedID(PHIEliminationID);
     AU.addRequiredID(PHIEliminationID);
+  }
+  
   AU.addRequiredID(TwoAddressInstructionPassID);
   MachineFunctionPass::getAnalysisUsage(AU);
 }

lib/CodeGen/RegAllocLinearScan.cpp

@@ -26,6 +26,7 @@
 #include "llvm/CodeGen/RegisterCoalescer.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/ADT/Statistic.h"
@@ -107,6 +108,8 @@ namespace {
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.addRequired<LiveIntervals>();
+      if (StrongPHIElim)
+        AU.addRequiredID(StrongPHIEliminationID);
       // Make sure PassManager knows which analyses to make available
       // to coalescing and which analyses coalescing invalidates.
       AU.addRequiredTransitive<RegisterCoalescer>();

lib/CodeGen/SimpleRegisterCoalescing.cpp

@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/RegisterCoalescer.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/SmallSet.h"
@@ -72,6 +73,9 @@ void SimpleRegisterCoalescing::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<MachineLoopInfo>();
   AU.addPreserved<MachineLoopInfo>();
   AU.addPreservedID(MachineDominatorsID);
+  if (StrongPHIElim)
+    AU.addPreservedID(StrongPHIEliminationID);
+  else
     AU.addPreservedID(PHIEliminationID);
   AU.addPreservedID(TwoAddressInstructionPassID);
   MachineFunctionPass::getAnalysisUsage(AU);

lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -37,6 +37,7 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/BitVector.h"
@@ -76,6 +77,9 @@ namespace {
       AU.addPreserved<LiveVariables>();
       AU.addPreservedID(MachineLoopInfoID);
       AU.addPreservedID(MachineDominatorsID);
+      if (StrongPHIElim)
+        AU.addPreservedID(StrongPHIEliminationID);
+      else
         AU.addPreservedID(PHIEliminationID);
       MachineFunctionPass::getAnalysisUsage(AU);
     }

lib/Target/TargetMachine.cpp

@@ -39,6 +39,7 @@ namespace llvm {
   bool RealignStack;
   bool VerboseAsm;
   bool DisableJumpTables;
+  bool StrongPHIElim;
 }
 
 static cl::opt<bool, true> PrintCode("print-machineinstrs",
@@ -157,6 +158,12 @@ DisableSwitchTables(cl::Hidden, "disable-jump-tables",
            cl::location(DisableJumpTables),
            cl::init(false));
 
+static cl::opt<bool, true>
+EnableStrongPHIElim(cl::Hidden, "strong-phi-elim",
+           cl::desc("Use strong PHI elimination."),
+           cl::location(StrongPHIElim),
+           cl::init(false));
+
 //---------------------------------------------------------------------------
 // TargetMachine Class
 //