[PATCH] D110560: [LiveInterval] Add RemoveDeadValNo argument to removeSegment(iterator)

[Jay Foad via Phabricator via llvm-commits]

foad created this revision.
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Add an optional bool RemoveDeadValNo argument to the
removeSegment(iterator) overload, for consistency with the other
overloads. This gives clients a way to remove dead valnos while also
getting an updated iterator returned (in the manner of vector::erase).

Use this to clean up some inefficient code in
LiveIntervals::repairOldRegInRange. NFC.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D110560

Files:
  llvm/include/llvm/CodeGen/LiveInterval.h
  llvm/lib/CodeGen/LiveInterval.cpp
  llvm/lib/CodeGen/LiveIntervals.cpp


Index: llvm/lib/CodeGen/LiveIntervals.cpp
===================================================================
--- llvm/lib/CodeGen/LiveIntervals.cpp
+++ llvm/lib/CodeGen/LiveIntervals.cpp
@@ -1607,17 +1607,9 @@
       if (MO.isDef()) {
         if (!isStartValid) {
           if (LII->end.isDead()) {
-            SlotIndex prevStart;
+            LII = LR.removeSegment(LII, true);
             if (LII != LR.begin())
-              prevStart = std::prev(LII)->start;
-
-            // FIXME: This could be more efficient if there was a
-            // removeSegment method that returned an iterator.
-            LR.removeSegment(*LII, true);
-            if (prevStart.isValid())
-              LII = LR.find(prevStart);
-            else
-              LII = LR.begin();
+              --LII;
           } else {
             LII->start = instrIdx.getRegSlot();
             LII->valno->def = instrIdx.getRegSlot();
Index: llvm/lib/CodeGen/LiveInterval.cpp
===================================================================
--- llvm/lib/CodeGen/LiveInterval.cpp
+++ llvm/lib/CodeGen/LiveInterval.cpp
@@ -592,21 +592,10 @@
   VNInfo *ValNo = I->valno;
   if (I->start == Start) {
     if (I->end == End) {
-      if (RemoveDeadValNo) {
-        // Check if val# is dead.
-        bool isDead = true;
-        for (const_iterator II = begin(), EE = end(); II != EE; ++II)
-          if (II != I && II->valno == ValNo) {
-            isDead = false;
-            break;
-          }
-        if (isDead) {
-          // Now that ValNo is dead, remove it.
-          markValNoForDeletion(ValNo);
-        }
-      }
-
       segments.erase(I);  // Removed the whole Segment.
+
+      if (RemoveDeadValNo)
+        removeValNoIfDead(ValNo);
     } else
       I->start = End;
     return;
@@ -627,6 +616,21 @@
   segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
 }
 
+LiveRange::iterator LiveRange::removeSegment(iterator I, bool RemoveDeadValNo) {
+  VNInfo *ValNo = I->valno;
+  I = segments.erase(I);
+  if (RemoveDeadValNo)
+    removeValNoIfDead(ValNo);
+  return I;
+}
+
+void LiveRange::removeValNoIfDead(VNInfo *ValNo) {
+  if (std::any_of(begin(), end(),
+                  [=](const Segment &S) { return S.valno == ValNo; }))
+    return;
+  markValNoForDeletion(ValNo);
+}
+
 /// removeValNo - Remove all the segments defined by the specified value#.
 /// Also remove the value# from value# list.
 void LiveRange::removeValNo(VNInfo *ValNo) {
Index: llvm/include/llvm/CodeGen/LiveInterval.h
===================================================================
--- llvm/include/llvm/CodeGen/LiveInterval.h
+++ llvm/include/llvm/CodeGen/LiveInterval.h
@@ -521,11 +521,11 @@
       removeSegment(S.start, S.end, RemoveDeadValNo);
     }
 
-    /// Remove segment pointed to by iterator @p I from this range.  This does
-    /// not remove dead value numbers.
-    iterator removeSegment(iterator I) {
-      return segments.erase(I);
-    }
+    /// Remove segment pointed to by iterator @p I from this range.
+    iterator removeSegment(iterator I, bool RemoveDeadValNo = false);
+
+    /// Mark \p ValNo for deletion if no segments in this range use it.
+    void removeValNoIfDead(VNInfo *ValNo);
 
     /// Query Liveness at Idx.
     /// The sub-instruction slot of Idx doesn't matter, only the instruction


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