[llvm] 87c0087 - SplitKit: Remove decade old live interval hack

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2021-09-15T17:35:59-04:00
New Revision: 87c00878d3ace60fe07cc2a9f8bd4566ab817d26

URL: https://github.com/llvm/llvm-project/commit/87c00878d3ace60fe07cc2a9f8bd4566ab817d26
DIFF: https://github.com/llvm/llvm-project/commit/87c00878d3ace60fe07cc2a9f8bd4566ab817d26.diff

LOG: SplitKit: Remove decade old live interval hack

This was trying to fixup broken live intervals coming out of the
coalescer. The verifier is more complete now and no tests seem to fail
without this.

Added: 
    

Modified: 
    llvm/lib/CodeGen/RegAllocGreedy.cpp
    llvm/lib/CodeGen/SplitKit.cpp
    llvm/lib/CodeGen/SplitKit.h

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
index 258946a03208..67fb8b4f8e5d 100644
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -2504,17 +2504,6 @@ unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
 
   SA->analyze(&VirtReg);
 
-  // FIXME: SplitAnalysis may repair broken live ranges coming from the
-  // coalescer. That may cause the range to become allocatable which means that
-  // tryRegionSplit won't be making progress. This check should be replaced with
-  // an assertion when the coalescer is fixed.
-  if (SA->didRepairRange()) {
-    // VirtReg has changed, so all cached queries are invalid.
-    Matrix->invalidateVirtRegs();
-    if (Register PhysReg = tryAssign(VirtReg, Order, NewVRegs, FixedRegisters))
-      return PhysReg;
-  }
-
   // First try to split around a region spanning multiple blocks. RS_Split2
   // ranges already made dubious progress with region splitting, so they go
   // straight to single block splitting.

diff  --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index 38493edf0af1..7f9518e4c075 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -50,7 +50,6 @@ STATISTIC(NumFinished, "Number of splits finished");
 STATISTIC(NumSimple,   "Number of splits that were simple");
 STATISTIC(NumCopies,   "Number of copies inserted for splitting");
 STATISTIC(NumRemats,   "Number of rematerialized defs for splitting");
-STATISTIC(NumRepairs,  "Number of invalid live ranges repaired");
 
 //===----------------------------------------------------------------------===//
 //                     Last Insert Point Analysis
@@ -160,7 +159,6 @@ void SplitAnalysis::clear() {
   UseBlocks.clear();
   ThroughBlocks.clear();
   CurLI = nullptr;
-  DidRepairRange = false;
 }
 
 /// analyzeUses - Count instructions, basic blocks, and loops using CurLI.
@@ -188,20 +186,7 @@ void SplitAnalysis::analyzeUses() {
                  UseSlots.end());
 
   // Compute per-live block info.
-  if (!calcLiveBlockInfo()) {
-    // FIXME: calcLiveBlockInfo found inconsistencies in the live range.
-    // I am looking at you, RegisterCoalescer!
-    DidRepairRange = true;
-    ++NumRepairs;
-    LLVM_DEBUG(dbgs() << "*** Fixing inconsistent live interval! ***\n");
-    const_cast<LiveIntervals&>(LIS)
-      .shrinkToUses(const_cast<LiveInterval*>(CurLI));
-    UseBlocks.clear();
-    ThroughBlocks.clear();
-    bool fixed = calcLiveBlockInfo();
-    (void)fixed;
-    assert(fixed && "Couldn't fix broken live interval");
-  }
+  calcLiveBlockInfo();
 
   LLVM_DEBUG(dbgs() << "Analyze counted " << UseSlots.size() << " instrs in "
                     << UseBlocks.size() << " blocks, through "
@@ -210,11 +195,11 @@ void SplitAnalysis::analyzeUses() {
 
 /// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
 /// where CurLI is live.
-bool SplitAnalysis::calcLiveBlockInfo() {
+void SplitAnalysis::calcLiveBlockInfo() {
   ThroughBlocks.resize(MF.getNumBlockIDs());
   NumThroughBlocks = NumGapBlocks = 0;
   if (CurLI->empty())
-    return true;
+    return;
 
   LiveInterval::const_iterator LVI = CurLI->begin();
   LiveInterval::const_iterator LVE = CurLI->end();
@@ -240,8 +225,7 @@ bool SplitAnalysis::calcLiveBlockInfo() {
       ThroughBlocks.set(BI.MBB->getNumber());
       // The range shouldn't end mid-block if there are no uses. This shouldn't
       // happen.
-      if (LVI->end < Stop)
-        return false;
+      assert(LVI->end >= Stop && "range ends mid block with no uses");
     } else {
       // This block has uses. Find the first and last uses in the block.
       BI.FirstInstr = *UseI;
@@ -312,7 +296,6 @@ bool SplitAnalysis::calcLiveBlockInfo() {
   }
 
   assert(getNumLiveBlocks() == countLiveBlocks(CurLI) && "Bad block count");
-  return true;
 }
 
 unsigned SplitAnalysis::countLiveBlocks(const LiveInterval *cli) const {

diff  --git a/llvm/lib/CodeGen/SplitKit.h b/llvm/lib/CodeGen/SplitKit.h
index fbcffacb49ab..902546fe16d8 100644
--- a/llvm/lib/CodeGen/SplitKit.h
+++ b/llvm/lib/CodeGen/SplitKit.h
@@ -160,14 +160,11 @@ class LLVM_LIBRARY_VISIBILITY SplitAnalysis {
   /// NumThroughBlocks - Number of live-through blocks.
   unsigned NumThroughBlocks;
 
-  /// DidRepairRange - analyze was forced to shrinkToUses().
-  bool DidRepairRange;
-
   // Sumarize statistics by counting instructions using CurLI.
   void analyzeUses();
 
   /// calcLiveBlockInfo - Compute per-block information about CurLI.
-  bool calcLiveBlockInfo();
+  void calcLiveBlockInfo();
 
 public:
   SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
@@ -177,11 +174,6 @@ class LLVM_LIBRARY_VISIBILITY SplitAnalysis {
   /// split.
   void analyze(const LiveInterval *li);
 
-  /// didRepairRange() - Returns true if CurLI was invalid and has been repaired
-  /// by analyze(). This really shouldn't happen, but sometimes the coalescer
-  /// can create live ranges that end in mid-air.
-  bool didRepairRange() const { return DidRepairRange; }
-
   /// clear - clear all data structures so SplitAnalysis is ready to analyze a
   /// new interval.
   void clear();