From 63449f93a0a9a30dc29e604eb14e81a668eb9d09 Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Wed, 10 Jan 2018 21:41:02 +0000
Subject: [PATCH] LiveRangeEdit: Simplify code; NFC

Simplify the code slightly: Instead of creating empty subranges in one
case and immediately removing them, do not create them in the first
place.

llvm-svn: 322226
---
 llvm/include/llvm/CodeGen/LiveRangeEdit.h |  8 +++----
 llvm/lib/CodeGen/LiveRangeEdit.cpp        | 26 ++++++++++++-----------
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/LiveRangeEdit.h b/llvm/include/llvm/CodeGen/LiveRangeEdit.h
index 84bccde0caa2..84ca51e3d72f 100644
--- a/llvm/include/llvm/CodeGen/LiveRangeEdit.h
+++ b/llvm/include/llvm/CodeGen/LiveRangeEdit.h
@@ -121,6 +121,9 @@ private:
   /// main live range of \p LI or in one of the matching subregister ranges.
   bool useIsKill(const LiveInterval &LI, const MachineOperand &MO) const;
 
+  /// Create a new empty interval based on OldReg.
+  LiveInterval &createEmptyIntervalFrom(unsigned OldReg, bool createSubRanges);
+
 public:
   /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
   /// @param parent The register being spilled or split.
@@ -174,16 +177,13 @@ public:
     return makeArrayRef(NewRegs).slice(FirstNew);
   }
 
-  /// createEmptyIntervalFrom - Create a new empty interval based on OldReg.
-  LiveInterval &createEmptyIntervalFrom(unsigned OldReg);
-
   /// createFrom - Create a new virtual register based on OldReg.
   unsigned createFrom(unsigned OldReg);
 
   /// create - Create a new register with the same class and original slot as
   /// parent.
   LiveInterval &createEmptyInterval() {
-    return createEmptyIntervalFrom(getReg());
+    return createEmptyIntervalFrom(getReg(), true);
   }
 
   unsigned create() { return createFrom(getReg()); }
diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index 86cfbd87f5b1..d00b36078672 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -31,21 +31,24 @@ STATISTIC(NumFracRanges,     "Number of live ranges fractured by DCE");
 
 void LiveRangeEdit::Delegate::anchor() { }
 
-LiveInterval &LiveRangeEdit::createEmptyIntervalFrom(unsigned OldReg) {
+LiveInterval &LiveRangeEdit::createEmptyIntervalFrom(unsigned OldReg,
+                                                     bool createSubRanges) {
   unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
-  if (VRM) {
+  if (VRM)
     VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));
-  }
+
   LiveInterval &LI = LIS.createEmptyInterval(VReg);
   if (Parent && !Parent->isSpillable())
     LI.markNotSpillable();
-  // Create empty subranges if the OldReg's interval has them. Do not create
-  // the main range here---it will be constructed later after the subranges
-  // have been finalized.
-  LiveInterval &OldLI = LIS.getInterval(OldReg);
-  VNInfo::Allocator &Alloc = LIS.getVNInfoAllocator();
-  for (LiveInterval::SubRange &S : OldLI.subranges())
-    LI.createSubRange(Alloc, S.LaneMask);
+  if (createSubRanges) {
+    // Create empty subranges if the OldReg's interval has them. Do not create
+    // the main range here---it will be constructed later after the subranges
+    // have been finalized.
+    LiveInterval &OldLI = LIS.getInterval(OldReg);
+    VNInfo::Allocator &Alloc = LIS.getVNInfoAllocator();
+    for (LiveInterval::SubRange &S : OldLI.subranges())
+      LI.createSubRange(Alloc, S.LaneMask);
+  }
   return LI;
 }
 
@@ -357,8 +360,7 @@ void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink,
     // LiveRangeEdit::DeadRemats and will be deleted after all the
     // allocations of the func are done.
     if (isOrigDef && DeadRemats && TII.isTriviallyReMaterializable(*MI, AA)) {
-      LiveInterval &NewLI = createEmptyIntervalFrom(Dest);
-      NewLI.removeEmptySubRanges();
+      LiveInterval &NewLI = createEmptyIntervalFrom(Dest, false);
       VNInfo *VNI = NewLI.getNextValue(Idx, LIS.getVNInfoAllocator());
       NewLI.addSegment(LiveInterval::Segment(Idx, Idx.getDeadSlot(), VNI));
       pop_back();