Handle reserved registers more accurately in handleMove().

Reserved register live ranges look like a set of dead defs - any uses of
reserved registers are ignored.

Instead of skipping the updating of reserved register operands entirely,
just ignore the use operands and treat the def operands normally.

No test case, handleMove() is not commonly used yet.

llvm-svn: 165060

1 files changed, 7 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index dca305849e5..141f8edc839 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1164,18 +1164,17 @@ private:
 
       unsigned Reg = MO.getReg();
 
-      // TODO: Currently we're skipping uses that are reserved or have no
-      // interval, but we're not updating their kills. This should be
-      // fixed.
-      if (TargetRegisterInfo::isPhysicalRegister(Reg) && LIS.isReserved(Reg))
-        continue;
+      // Don't track uses of reserved registers - they're not accurate.
+      // Reserved register live ranges look like a set of dead defs.
+      bool Resv =
+        TargetRegisterInfo::isPhysicalRegister(Reg) && LIS.isReserved(Reg);
 
       // Collect ranges for register units. These live ranges are computed on
       // demand, so just skip any that haven't been computed yet.
       if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
         for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
           if (LiveInterval *LI = LIS.getCachedRegUnit(*Units))
-            collectRanges(MO, LI, Entering, Internal, Exiting, OldIdx);
+            collectRanges(MO, LI, Entering, Internal, Exiting, OldIdx, Resv);
       } else {
         // Collect ranges for individual virtual registers.
         collectRanges(MO, &LIS.getInterval(Reg),
@@ -1186,8 +1185,8 @@ private:
 
   void collectRanges(const MachineOperand &MO, LiveInterval *LI,
                      RangeSet &Entering, RangeSet &Internal, RangeSet &Exiting,
-                     SlotIndex OldIdx) {
-    if (MO.readsReg()) {
+                     SlotIndex OldIdx, bool IgnoreReads = false) {
+    if (!IgnoreReads && MO.readsReg()) {
       LiveRange* LR = LI->getLiveRangeContaining(OldIdx);
       if (LR != 0)
         Entering.insert(std::make_pair(LI, LR));