Add a -new-live-intervals experimental option.

This option replaces the existing live interval computation with one
based on LiveRangeCalc.cpp. The new algorithm does not depend on
LiveVariables, and it can be run at any time, before or after leaving
SSA form.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160892 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index a344b1ff1b5947016b80971f11630c5cada7b0f2..fe22d8af027db7217dc4014d24159c266a87d3cd 100644 (file)
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -375,6 +375,7 @@ namespace llvm {
 
     void computeLiveInRegUnits();
     void computeRegUnitInterval(LiveInterval*);
+    void computeVirtRegInterval(LiveInterval*);
 
     class HMEditor;
   };

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 819707f59f55143c8d75650753c9e2b4956d76ff..bc0ec157f6231d40c705f005da2a10f29c4b4491 100644 (file)
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
@@ -38,6 +39,11 @@
 #include <cmath>
 using namespace llvm;
 
+// Switch to the new experimental algorithm for computing live intervals.
+static cl::opt<bool>
+NewLiveIntervals("new-live-intervals", cl::Hidden,
+                 cl::desc("Use new algorithm forcomputing live intervals"));
+
 char LiveIntervals::ID = 0;
 INITIALIZE_PASS_BEGIN(LiveIntervals, "liveintervals",
                 "Live Interval Analysis", false, false)
@@ -105,7 +111,25 @@ bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
   AllocatableRegs = TRI->getAllocatableSet(fn);
   ReservedRegs = TRI->getReservedRegs(fn);
 
-  computeIntervals();
+  // Allocate space for all virtual registers.
+  VirtRegIntervals.resize(MRI->getNumVirtRegs());
+
+  if (NewLiveIntervals) {
+    // This is the new way of computing live intervals.
+    // It is independent of LiveVariables, and it can run at any time.
+    for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
+      unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
+      if (MRI->reg_nodbg_empty(Reg))
+        continue;
+      LiveInterval *LI = createInterval(Reg);
+      VirtRegIntervals[Reg] = LI;
+      computeVirtRegInterval(LI);
+    }
+  } else {
+    // This is the old way of computing live intervals.
+    // It depends on LiveVariables.
+    computeIntervals();
+  }
   computeLiveInRegUnits();
 
   DEBUG(dump());
@@ -442,6 +466,17 @@ LiveInterval* LiveIntervals::createInterval(unsigned reg) {
 }
 
 
+/// computeVirtRegInterval - Compute the live interval of a virtual register,
+/// based on defs and uses.
+void LiveIntervals::computeVirtRegInterval(LiveInterval *LI) {
+  assert(LRCalc && "LRCalc not initialized.");
+  assert(LI->empty() && "Should only compute empty intervals.");
+  LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
+  LRCalc->createDeadDefs(LI);
+  LRCalc->extendToUses(LI);
+}
+
+
 //===----------------------------------------------------------------------===//
 //                           Register Unit Liveness
 //===----------------------------------------------------------------------===//