[PATCH] D101064: [WIP] improve debug-info in stack-slot-coloring

[Markus Lavin via Phabricator via llvm-commits]

markus updated this revision to Diff 341102.
markus edited the summary of this revision.
markus added a comment.

Prototype of the 'terminate debug-info for slots when they go out of liveness, before being merged' idea in the TR.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101064/new/

https://reviews.llvm.org/D101064

Files:
  llvm/lib/CodeGen/StackSlotColoring.cpp


Index: llvm/lib/CodeGen/StackSlotColoring.cpp
===================================================================
--- llvm/lib/CodeGen/StackSlotColoring.cpp
+++ llvm/lib/CodeGen/StackSlotColoring.cpp
@@ -60,6 +60,7 @@
 
   class StackSlotColoring : public MachineFunctionPass {
     LiveStacks* LS;
+    SlotIndexes *Indexes;
     MachineFrameInfo *MFI;
     const TargetInstrInfo  *TII;
     const MachineBlockFrequencyInfo *MBFI;
@@ -72,6 +73,8 @@
     // to be careful that renames like [FI0, FI1] -> [FI1, FI2] do not
     // become FI0 -> FI1 -> FI2.
     SmallVector<SmallVector<MachineMemOperand *, 8>, 16> SSRefs;
+    DenseMap<unsigned, SmallVector<MachineInstr *, 8>> SS2DbgValues;
+    DenseMap<unsigned, LiveInterval *> SS2LI;
 
     // OrigAlignments - Alignments of stack objects before coloring.
     SmallVector<Align, 16> OrigAlignments;
@@ -123,6 +126,7 @@
     void RewriteInstruction(MachineInstr &MI, SmallVectorImpl<int> &SlotMapping,
                             MachineFunction &MF);
     bool RemoveDeadStores(MachineBasicBlock* MBB);
+    void TerminateDbgForSlot(unsigned FI, LiveInterval *LI);
   };
 
 } // end anonymous namespace
@@ -303,6 +307,9 @@
   Assignments[Color].push_back(li);
   LLVM_DEBUG(dbgs() << "Assigning fi#" << FI << " to fi#" << Color << "\n");
 
+  if (FI != Color)
+    TerminateDbgForSlot(Color, SS2LI[Color]);
+
   // Change size and alignment of the allocated slot. If there are multiple
   // objects sharing the same slot, then make sure the size and alignment
   // are large enough for all.
@@ -476,6 +483,24 @@
   return changed;
 }
 
+/// Terminate the DBG_VALUE(s) of variables residing in stack-slot with
+/// frame-index FI at the Segment.end points of LI.
+void StackSlotColoring::TerminateDbgForSlot(unsigned FI, LiveInterval *LI) {
+  for (auto &Seg : *LI) {
+    if (auto *SegEndMI = Indexes->getInstructionFromIndex(Seg.end)) {
+      for (auto *DbgValue : SS2DbgValues[FI]) {
+        auto ItMI = SegEndMI->getIterator();
+        BuildMI(*SegEndMI->getParent(), ItMI, DbgValue->getDebugLoc(),
+                TII->get(TargetOpcode::DBG_VALUE))
+            .addReg(0) // $noreg
+            .add(DbgValue->getOperand(1))
+            .add(DbgValue->getOperand(2))
+            .add(DbgValue->getOperand(3));
+      }
+    }
+  }
+}
+
 bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
   LLVM_DEBUG({
     dbgs() << "********** Stack Slot Coloring **********\n"
@@ -489,6 +514,7 @@
   TII = MF.getSubtarget().getInstrInfo();
   LS = &getAnalysis<LiveStacks>();
   MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+  Indexes = &getAnalysis<SlotIndexes>();
 
   bool Changed = false;
 
@@ -507,6 +533,24 @@
   // Gather spill slot references
   ScanForSpillSlotRefs(MF);
   InitializeSlots();
+
+  // Create mapping of SS -> LiveInterval.
+  for (unsigned i = 0; i < SSIntervals.size(); i++) {
+    LiveInterval *li = SSIntervals[i];
+    int SS = Register::stackSlot2Index(li->reg());
+    SS2LI[SS] = li;
+  }
+
+  // Create mapping of SS -> DBG_VALUE(s).
+  for (MachineBasicBlock &MBB : MF) {
+    for (MachineInstr &MI : MBB) {
+      if (MI.isDebugValue() && MI.getOperand(0).isFI()) {
+        auto SS = MI.getOperand(0).getIndex();
+        SS2DbgValues[SS].push_back(&MI);
+      }
+    }
+  }
+
   Changed = ColorSlots(MF);
 
   for (int &Next : NextColors)


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