From 66a1b83bf93ec46f6d7a06c47d5981ae154f9ea0 Mon Sep 17 00:00:00 2001
From: Denis Antrushin <dantrushin@gmail.com>
Date: Thu, 4 Jun 2020 19:11:13 +0300
Subject: [PATCH] [TargetLowering][NFC] More efficient emitPatchpoint().

Current implementation of emitPatchpoint() is very inefficient:
for every FrameIndex operand if creates new MachineInstr with
that operand expanded and all other copied 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.

Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D81181
---
 llvm/lib/CodeGen/TargetLoweringBase.cpp | 34 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 62c3af9..41cfa99 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -1023,20 +1023,25 @@ TargetLoweringBase::emitPatchPoint(MachineInstr &InitialMI,
   // 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) {
-    MachineOperand &MO = MI->getOperand(OperIdx);
-    if (!MO.isFI())
+  if (!llvm::any_of(MI->operands(),
+                    [](MachineOperand &Operand) { return Operand.isFI(); }))
+    return MBB;
+
+  MachineInstrBuilder MIB = BuildMI(MF, MI->getDebugLoc(), MI->getDesc());
+
+  // Inherit previous memory operands.
+  MIB.cloneMemRefs(*MI);
+
+  for (auto &MO : MI->operands()) {
+    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 +1060,7 @@ TargetLoweringBase::emitPatchPoint(MachineInstr &InitialMI,
       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 +1075,9 @@ TargetLoweringBase::emitPatchPoint(MachineInstr &InitialMI,
           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;
 }
 
-- 
2.7.4