LiveIntervalAnalysis: Remove LiveVariables requirement

This requirement was a huge hack to keep LiveVariables alive because it
was optionally used by TwoAddressInstructionPass and PHIElimination.
However we have AnalysisUsage::addUsedIfAvailable() which we can use in
those passes.

llvm-svn: 260806

3 files changed, 3 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index bab3d0d01bd..b91e7176a8f 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -9,8 +9,7 @@
 //
 // This file implements the LiveInterval analysis pass which is used
 // by the Linear Scan Register allocator. This pass linearizes the
-// basic blocks of the function in DFS order and uses the
-// LiveVariables pass to conservatively compute live intervals for
+// basic blocks of the function in DFS order and computes live intervals for
 // each virtual and physical register.
 //
 //===----------------------------------------------------------------------===//
@@ -48,7 +47,6 @@ char &llvm::LiveIntervalsID = LiveIntervals::ID;
 INITIALIZE_PASS_BEGIN(LiveIntervals, "liveintervals",
                 "Live Interval Analysis", false, false)
 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(LiveVariables)
 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
 INITIALIZE_PASS_END(LiveIntervals, "liveintervals",
@@ -77,10 +75,6 @@ void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
   AU.addRequired<AAResultsWrapperPass>();
   AU.addPreserved<AAResultsWrapperPass>();
-  // LiveVariables isn't really required by this analysis, it is only required
-  // here to make sure it is live during TwoAddressInstructionPass and
-  // PHIElimination. This is temporary.
-  AU.addRequired<LiveVariables>();
   AU.addPreserved<LiveVariables>();
   AU.addPreservedID(MachineLoopInfoID);
   AU.addRequiredTransitiveID(MachineDominatorsID);
diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index 2c937926d0a..0472378aeee 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -121,6 +121,7 @@ INITIALIZE_PASS_END(PHIElimination, "phi-node-elimination",
                     "Eliminate PHI nodes for register allocation", false, false)
 
 void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addUsedIfAvailable<LiveVariables>();
   AU.addPreserved<LiveVariables>();
   AU.addPreserved<SlotIndexes>();
   AU.addPreserved<LiveIntervals>();
diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index e8009cc8337..379de8836de 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -157,6 +157,7 @@ public:
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesCFG();
     AU.addRequired<AAResultsWrapperPass>();
+    AU.addUsedIfAvailable<LiveVariables>();
     AU.addPreserved<LiveVariables>();
     AU.addPreserved<SlotIndexes>();
     AU.addPreserved<LiveIntervals>();