Save LaneMask with livein registers

With subregister liveness enabled we can detect the case where only
parts of a register are live in, this is expressed as a 32bit lanemask.
The current code only keeps registers in the live-in list and therefore
enumerated all subregisters affected by the lanemask. This turned out to
be too conservative as the subregister may also cover additional parts
of the lanemask which are not live. Expressing a given lanemask by
enumerating a minimum set of subregisters is computationally expensive
so the best solution is to simply change the live-in list to store the
lanemasks as well. This will reduce memory usage for targets using
subregister liveness and slightly increase it for other targets

Differential Revision: http://reviews.llvm.org/D12442

llvm-svn: 247171

1 files changed, 40 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index b2bbe09176d..025c0af0e43 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -28,6 +28,7 @@
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
@@ -277,8 +278,10 @@ void MachineBasicBlock::print(raw_ostream &OS, ModuleSlotTracker &MST,
   if (!livein_empty()) {
     if (Indexes) OS << '\t';
     OS << "    Live Ins:";
-    for (unsigned LI : make_range(livein_begin(), livein_end())) {
-      OS << ' ' << PrintReg(LI, TRI);
+    for (const auto &LI : make_range(livein_begin(), livein_end())) {
+      OS << ' ' << PrintReg(LI.PhysReg, TRI);
+      if (LI.LaneMask != ~0u)
+        OS << format(":%08X", LI.LaneMask);
     }
     OS << '\n';
   }
@@ -321,15 +324,43 @@ void MachineBasicBlock::printAsOperand(raw_ostream &OS,
   OS << "BB#" << getNumber();
 }
 
-void MachineBasicBlock::removeLiveIn(MCPhysReg Reg) {
-  LiveInVector::iterator I = std::find(LiveIns.begin(), LiveIns.end(), Reg);
-  if (I != LiveIns.end())
+void MachineBasicBlock::removeLiveIn(MCPhysReg Reg, unsigned LaneMask) {
+  LiveInVector::iterator I = std::find_if(
+      LiveIns.begin(), LiveIns.end(),
+      [Reg] (const RegisterMaskPair &LI) { return LI.PhysReg == Reg; });
+  if (I == LiveIns.end())
+    return;
+
+  I->LaneMask &= ~LaneMask;
+  if (I->LaneMask == 0)
     LiveIns.erase(I);
 }
 
-bool MachineBasicBlock::isLiveIn(MCPhysReg Reg) const {
-  livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
-  return I != livein_end();
+bool MachineBasicBlock::isLiveIn(MCPhysReg Reg, unsigned LaneMask) const {
+  livein_iterator I = std::find_if(
+      LiveIns.begin(), LiveIns.end(),
+      [Reg] (const RegisterMaskPair &LI) { return LI.PhysReg == Reg; });
+  return I != livein_end() && (I->LaneMask & LaneMask) != 0;
+}
+
+void MachineBasicBlock::sortUniqueLiveIns() {
+  std::sort(LiveIns.begin(), LiveIns.end(),
+            [](const RegisterMaskPair &LI0, const RegisterMaskPair &LI1) {
+              return LI0.PhysReg < LI1.PhysReg;
+            });
+  // Liveins are sorted by physreg now we can merge their lanemasks.
+  LiveInVector::const_iterator I = LiveIns.begin();
+  LiveInVector::const_iterator J;
+  LiveInVector::iterator Out = LiveIns.begin();
+  for (; I != LiveIns.end(); ++Out, I = J) {
+    unsigned PhysReg = I->PhysReg;
+    unsigned LaneMask = I->LaneMask;
+    for (J = std::next(I); J != LiveIns.end() && J->PhysReg == PhysReg; ++J)
+      LaneMask |= J->LaneMask;
+    Out->PhysReg = PhysReg;
+    Out->LaneMask = LaneMask;
+  }
+  LiveIns.erase(Out, LiveIns.end());
 }
 
 unsigned
@@ -803,7 +834,7 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
         i->getOperand(ni+1).setMBB(NMBB);
 
   // Inherit live-ins from the successor
-  for (unsigned LI : Succ->liveins())
+  for (const auto &LI : Succ->liveins())
     NMBB->addLiveIn(LI);
 
   // Update LiveVariables.