[PATCH] D150855: MachineCombiner: consider all uses in getLatency()

[Ramkumar Ramachandra via Phabricator via llvm-commits]

artagnon created this revision.
artagnon added reviewers: spatel, dexonsmith, asi-sc.
Herald added subscribers: StephenFan, hiraditya.
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getLatency() was considering only the first use when computing operand
latency. Fix this.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150855

Files:
  llvm/lib/CodeGen/MachineCombiner.cpp


Index: llvm/lib/CodeGen/MachineCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/MachineCombiner.cpp
+++ llvm/lib/CodeGen/MachineCombiner.cpp
@@ -217,12 +217,10 @@
   // are tracked in the InstrIdxForVirtReg map depth is looked up in InstrDepth
   for (auto *InstrPtr : InsInstrs) { // for each Use
     unsigned IDepth = 0;
-    for (const MachineOperand &MO : InstrPtr->operands()) {
+    for (const MachineOperand &MO : InstrPtr->uses()) {
       // Check for virtual register operand.
       if (!(MO.isReg() && MO.getReg().isVirtual()))
         continue;
-      if (!MO.isUse())
-        continue;
       unsigned DepthOp = 0;
       unsigned LatencyOp = 0;
       DenseMap<unsigned, unsigned>::iterator II =
@@ -272,27 +270,21 @@
   // Check each definition in NewRoot and compute the latency
   unsigned NewRootLatency = 0;
 
-  for (const MachineOperand &MO : NewRoot->operands()) {
+  for (const MachineOperand &MO : NewRoot->defs()) {
     // Check for virtual register operand.
     if (!(MO.isReg() && MO.getReg().isVirtual()))
       continue;
-    if (!MO.isDef())
-      continue;
-    // Get the first instruction that uses MO
-    MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(MO.getReg());
-    RI++;
-    if (RI == MRI->reg_end())
-      continue;
-    MachineInstr *UseMO = RI->getParent();
-    unsigned LatencyOp = 0;
-    if (UseMO && BlockTrace.isDepInTrace(*Root, *UseMO)) {
-      LatencyOp = TSchedModel.computeOperandLatency(
-          NewRoot, NewRoot->findRegisterDefOperandIdx(MO.getReg()), UseMO,
-          UseMO->findRegisterUseOperandIdx(MO.getReg()));
-    } else {
-      LatencyOp = TSchedModel.computeInstrLatency(NewRoot);
+    for (MachineInstr &UseInstr : MRI->use_instructions(MO.getReg())) {
+      unsigned LatencyOp = 0;
+      if (BlockTrace.isDepInTrace(*Root, UseInstr)) {
+        LatencyOp = TSchedModel.computeOperandLatency(
+            NewRoot, NewRoot->findRegisterDefOperandIdx(MO.getReg()), &UseInstr,
+            UseInstr.findRegisterUseOperandIdx(MO.getReg()));
+      } else {
+        LatencyOp = TSchedModel.computeInstrLatency(NewRoot);
+      }
+      NewRootLatency = std::max(NewRootLatency, LatencyOp);
     }
-    NewRootLatency = std::max(NewRootLatency, LatencyOp);
   }
   return NewRootLatency;
 }


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