[llvm] 175e0dd - [MachineLateInstrsCleanup] Minor fixing (NFC). (#117816)

[via llvm-commits]

Author: Jonas Paulsson
Date: 2024-11-27T01:41:42+01:00
New Revision: 175e0dd4223b7678f660519a9342282e8b226093

URL: https://github.com/llvm/llvm-project/commit/175e0dd4223b7678f660519a9342282e8b226093
DIFF: https://github.com/llvm/llvm-project/commit/175e0dd4223b7678f660519a9342282e8b226093.diff

LOG: [MachineLateInstrsCleanup] Minor fixing (NFC). (#117816)

With cb57b7a7, MachineLateInstrsCleanup switched to using a map to keep
track of kill flags to remedy compile time regressions seen with huge
functions. It seems that the comment above clearKillsForDef() became stale with
that commit, and also that one of the arguments to it became unused,
both of which this patch fixes.

Added: 
    

Modified: 
    llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp b/llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp
index 14a49853f68b8e..6399e8a9523685 100644
--- a/llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp
+++ b/llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp
@@ -57,7 +57,6 @@ class MachineLateInstrsCleanup : public MachineFunctionPass {
 
   void removeRedundantDef(MachineInstr *MI);
   void clearKillsForDef(Register Reg, MachineBasicBlock *MBB,
-                        MachineBasicBlock::iterator I,
                         BitVector &VisitedPreds);
 
 public:
@@ -110,14 +109,11 @@ bool MachineLateInstrsCleanup::runOnMachineFunction(MachineFunction &MF) {
   return Changed;
 }
 
-// Clear any previous kill flag on Reg found before I in MBB. Walk backwards
-// in MBB and if needed continue in predecessors until a use/def of Reg is
-// encountered. This seems to be faster in practice than tracking kill flags
-// in a map.
-void MachineLateInstrsCleanup::
-clearKillsForDef(Register Reg, MachineBasicBlock *MBB,
-                 MachineBasicBlock::iterator I,
-                 BitVector &VisitedPreds) {
+// Clear any preceding kill flag on Reg after removing a redundant
+// definition.
+void MachineLateInstrsCleanup::clearKillsForDef(Register Reg,
+                                                MachineBasicBlock *MBB,
+                                                BitVector &VisitedPreds) {
   VisitedPreds.set(MBB->getNumber());
 
   // Kill flag in MBB
@@ -137,13 +133,13 @@ clearKillsForDef(Register Reg, MachineBasicBlock *MBB,
   assert(!MBB->pred_empty() && "Predecessor def not found!");
   for (MachineBasicBlock *Pred : MBB->predecessors())
     if (!VisitedPreds.test(Pred->getNumber()))
-      clearKillsForDef(Reg, Pred, Pred->end(), VisitedPreds);
+      clearKillsForDef(Reg, Pred, VisitedPreds);
 }
 
 void MachineLateInstrsCleanup::removeRedundantDef(MachineInstr *MI) {
   Register Reg = MI->getOperand(0).getReg();
   BitVector VisitedPreds(MI->getMF()->getNumBlockIDs());
-  clearKillsForDef(Reg, MI->getParent(), MI->getIterator(), VisitedPreds);
+  clearKillsForDef(Reg, MI->getParent(), VisitedPreds);
   MI->eraseFromParent();
   ++NumRemoved;
 }