LiveIntervals: Use BumpPtrAllocator

[arsenm]

No description provided.

[arsenm]

• LiveIntervals: Use BumpPtrAllocator #127057 👈 (View in Graphite)
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[llvmbot]

@llvm/pr-subscribers-llvm-regalloc

Author: Matt Arsenault (arsenm)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/127057.diff

2 Files Affected:

• (modified) llvm/include/llvm/CodeGen/LiveIntervals.h (+8-4)
• (modified) llvm/lib/CodeGen/LiveIntervals.cpp (+5-4)

diff --git a/llvm/include/llvm/CodeGen/LiveIntervals.h b/llvm/include/llvm/CodeGen/LiveIntervals.h
index 708917be497ef..65b59a9d8b41c 100644
--- a/llvm/include/llvm/CodeGen/LiveIntervals.h
+++ b/llvm/include/llvm/CodeGen/LiveIntervals.h
@@ -30,6 +30,7 @@
 #include "llvm/CodeGen/SlotIndexes.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/MC/LaneBitmask.h"
+#include "llvm/Support/Allocator.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -64,6 +65,8 @@ class LiveIntervals {
   MachineDominatorTree *DomTree = nullptr;
   std::unique_ptr<LiveIntervalCalc> LICalc;
 
+  BumpPtrAllocator Allocator;
+
   /// Special pool allocator for VNInfo's (LiveInterval val#).
   VNInfo::Allocator VNInfoAllocator;
 
@@ -170,7 +173,7 @@ class LiveIntervals {
   /// Interval removal.
   void removeInterval(Register Reg) {
     auto &Interval = VirtRegIntervals[Reg];
-    delete Interval;
+    Allocator.Deallocate(Interval);
     Interval = nullptr;
   }
 
@@ -416,7 +419,8 @@ class LiveIntervals {
     if (!LR) {
       // Compute missing ranges on demand.
       // Use segment set to speed-up initial computation of the live range.
-      RegUnitRanges[Unit] = LR = new LiveRange(UseSegmentSetForPhysRegs);
+      RegUnitRanges[Unit] = LR = new (Allocator.Allocate<LiveRange>())
+          LiveRange(UseSegmentSetForPhysRegs);
       computeRegUnitRange(*LR, Unit);
     }
     return *LR;
@@ -433,7 +437,7 @@ class LiveIntervals {
   /// Remove computed live range for register unit \p Unit. Subsequent uses
   /// should rely on on-demand recomputation.
   void removeRegUnit(unsigned Unit) {
-    delete RegUnitRanges[Unit];
+    Allocator.Deallocate(RegUnitRanges[Unit]);
     RegUnitRanges[Unit] = nullptr;
   }
 
@@ -481,7 +485,7 @@ class LiveIntervals {
   bool computeDeadValues(LiveInterval &LI,
                          SmallVectorImpl<MachineInstr *> *dead);
 
-  static LiveInterval *createInterval(Register Reg);
+  LiveInterval *createInterval(Register Reg);
 
   void printInstrs(raw_ostream &O) const;
   void dumpInstrs() const;
diff --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp
index 3485a27335f13..f12bf87023979 100644
--- a/llvm/lib/CodeGen/LiveIntervals.cpp
+++ b/llvm/lib/CodeGen/LiveIntervals.cpp
@@ -144,14 +144,14 @@ bool LiveIntervals::invalidate(
 void LiveIntervals::clear() {
   // Free the live intervals themselves.
   for (unsigned i = 0, e = VirtRegIntervals.size(); i != e; ++i)
-    delete VirtRegIntervals[Register::index2VirtReg(i)];
+    Allocator.Deallocate(VirtRegIntervals[Register::index2VirtReg(i)]);
   VirtRegIntervals.clear();
   RegMaskSlots.clear();
   RegMaskBits.clear();
   RegMaskBlocks.clear();
 
   for (LiveRange *LR : RegUnitRanges)
-    delete LR;
+    Allocator.Deallocate(LR);
   RegUnitRanges.clear();
 
   // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
@@ -222,7 +222,7 @@ LLVM_DUMP_METHOD void LiveIntervals::dump() const { print(dbgs()); }
 
 LiveInterval *LiveIntervals::createInterval(Register reg) {
   float Weight = reg.isPhysical() ? huge_valf : 0.0F;
-  return new LiveInterval(reg, Weight);
+  return new (Allocator.Allocate<LiveInterval>()) LiveInterval(reg, Weight);
 }
 
 /// Compute the live interval of a virtual register, based on defs and uses.
@@ -374,7 +374,8 @@ void LiveIntervals::computeLiveInRegUnits() {
         LiveRange *LR = RegUnitRanges[Unit];
         if (!LR) {
           // Use segment set to speed-up initial computation of the live range.
-          LR = RegUnitRanges[Unit] = new LiveRange(UseSegmentSetForPhysRegs);
+          LR = RegUnitRanges[Unit] = new (Allocator.Allocate<LiveRange>())
+              LiveRange(UseSegmentSetForPhysRegs);
           NewRanges.push_back(Unit);
         }
         VNInfo *VNI = LR->createDeadDef(Begin, getVNInfoAllocator());

[jayfoad]

Seems reasonable but do you have any performance data? Have you tried it with llvm-compile-time-tracker.com? And does it increase memory usage measurably, since BumpPtrAllocator::Deallocate does nothing?

[jayfoad]

Comment saying what this is used for?

[arsenm]

Seems reasonable but do you have any performance data?

No, I did this months ago and wanted to find something, but forgot about it and figured the tracker is the easiest way to test. I don't actually know how to submit branches there. @nikic?

[nikic]

LiveRange is not POD, so isn't this going to leak big time?

You need to use SpecificBumpPtrAllocator if you want to run destructors.

[nikic]

Current max-rss results: https://llvm-compile-time-tracker.com/compare.php?from=8600d89e55b866186a2dad2e2b4c85bd96150375&to=a2ee139249e919ae4a4ace66870685ea333ef30e&stat=max-rss 30% increase for the clang build. Hopefully this is due to not using SpecificBumpPtrAllocator...

[nikic]

With the new commit memory usage is a better but still +16% on clang: http://llvm-compile-time-tracker.com/compare.php?from=8600d89e55b866186a2dad2e2b4c85bd96150375&to=bd8b3bc6f30b78b51fde4b7fae7bcd67963117fb&stat=max-rss

[nikic]

Need this for LiveRange as well, as it contains vectors.