[PATCH] D81181: [TargetLowering][NFC] More efficient emitPatchpoint().

[Denis Antrushin via Phabricator via llvm-commits]

dantrushin created this revision.
dantrushin added reviewers: efriedma, craig.topper, reames.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Current implementation of emitPatchpoint() is very inefficient:
for every FrameIndex operand if creates new MachineInstr with
that operand expanded and all other copies as is.
Since PATCHPOINT/STATEPOINT instructions may have *a lot* of
FrameIndex operands, we end up creating and erasing many
machine instructions. But we can do it in single pass, with only
one new machine instruction generated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D81181

Files:
  llvm/lib/CodeGen/TargetLoweringBase.cpp


Index: llvm/lib/CodeGen/TargetLoweringBase.cpp
===================================================================
--- llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -1023,20 +1023,34 @@
   // all stack slots), but we need to handle the different type of stackmap
   // operands and memory effects here.
 
-  // MI changes inside this loop as we grow operands.
-  for(unsigned OperIdx = 0; OperIdx != MI->getNumOperands(); ++OperIdx) {
+  unsigned OperIdx = 0;
+  unsigned NumOpers = MI->getNumOperands();
+  for (; OperIdx < NumOpers; ++OperIdx)
+    if (MI->getOperand(OperIdx).isFI())
+      break;
+
+  if (OperIdx == NumOpers)
+    return MBB; // No frame indices seen, nothing to do.
+
+  MachineInstrBuilder MIB = BuildMI(MF, MI->getDebugLoc(), MI->getDesc());
+
+  for (unsigned i = 0; i < OperIdx; ++i)
+    MIB.add(MI->getOperand(i));
+
+  // Inherit previous memory operands.
+  MIB.cloneMemRefs(*MI);
+
+  for (; OperIdx < NumOpers; ++OperIdx) {
     MachineOperand &MO = MI->getOperand(OperIdx);
-    if (!MO.isFI())
+    if (!MO.isFI()) {
+      MIB.add(MI->getOperand(OperIdx));
       continue;
+    }
 
     // foldMemoryOperand builds a new MI after replacing a single FI operand
     // with the canonical set of five x86 addressing-mode operands.
     int FI = MO.getIndex();
-    MachineInstrBuilder MIB = BuildMI(MF, MI->getDebugLoc(), MI->getDesc());
 
-    // Copy operands before the frame-index.
-    for (unsigned i = 0; i < OperIdx; ++i)
-      MIB.add(MI->getOperand(i));
     // Add frame index operands recognized by stackmaps.cpp
     if (MFI.isStatepointSpillSlotObjectIndex(FI)) {
       // indirect-mem-ref tag, size, #FI, offset.
@@ -1055,12 +1069,7 @@
       MIB.add(MI->getOperand(OperIdx));
       MIB.addImm(0);
     }
-    // Copy the operands after the frame index.
-    for (unsigned i = OperIdx + 1; i != MI->getNumOperands(); ++i)
-      MIB.add(MI->getOperand(i));
 
-    // Inherit previous memory operands.
-    MIB.cloneMemRefs(*MI);
     assert(MIB->mayLoad() && "Folded a stackmap use to a non-load!");
 
     // Add a new memory operand for this FI.
@@ -1075,13 +1084,9 @@
           MF.getDataLayout().getPointerSize(), MFI.getObjectAlign(FI));
       MIB->addMemOperand(MF, MMO);
     }
-
-    // Replace the instruction and update the operand index.
-    MBB->insert(MachineBasicBlock::iterator(MI), MIB);
-    OperIdx += (MIB->getNumOperands() - MI->getNumOperands()) - 1;
-    MI->eraseFromParent();
-    MI = MIB;
   }
+  MBB->insert(MachineBasicBlock::iterator(MI), MIB);
+  MI->eraseFromParent();
   return MBB;
 }
 


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