[VPlan] Speed up VPSlotTracker by using ModuleSlotTracker

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -1495,13 +1495,7 @@ void VPSlotTracker::assignName(const VPValue *V) {
 
   // Use the name of the underlying Value, wrapped in "ir<>", and versioned by
   // appending ".Number" to the name if there are multiple uses.
-  std::string Name;
-  if (UV) {
-    raw_string_ostream S(Name);
-    UV->printAsOperand(S, false);
-  } else
-    Name = VPI->getName();
-
+  std::string Name = getName(V);
   assert(!Name.empty() && "Name cannot be empty.");
   StringRef Prefix = UV ? "ir<" : "vp<%";
   std::string BaseName = (Twine(Prefix) + Name + Twine(">")).str();
@@ -1546,6 +1540,34 @@ void VPSlotTracker::assignNames(const VPBasicBlock *VPBB) {
       assignName(Def);
 }
 
+std::string VPSlotTracker::getName(const VPValue *V) {
+  auto *UV = V->getUnderlyingValue();
+  auto *VPI = dyn_cast_or_null<VPInstruction>(V->getDefiningRecipe());
+  if (!UV)
+    return VPI->getName().str();
+
+  std::string Name;
+  raw_string_ostream S(Name);
+  if (MST) {
+    UV->printAsOperand(S, false, *MST);
+  } else if (isa<Instruction>(UV) && !UV->hasName()) {
+    // Lazily create the ModuleSlotTracker when we first hit an unnamed
+    // instruction
+    auto *IUV = cast<Instruction>(UV);
+    // This check is required to support unit tests with incomplete IR.
+    if (IUV->getParent()) {
+      MST = std::make_unique<ModuleSlotTracker>(IUV->getModule());
+      MST->incorporateFunction(*IUV->getFunction());
+    } else {
+      MST = std::make_unique<ModuleSlotTracker>(nullptr);
+    }
+    UV->printAsOperand(S, false, *MST);
+  } else {
+    UV->printAsOperand(S, false);
+  }
+  return Name;
+}
+
 std::string VPSlotTracker::getOrCreateName(const VPValue *V) const {
   std::string Name = VPValue2Name.lookup(V);
   if (!Name.empty())

llvm/lib/Transforms/Vectorize/VPlanHelpers.h

@@ -23,6 +23,7 @@
 #include "llvm/Analysis/DomTreeUpdater.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/DebugLoc.h"
+#include "llvm/IR/ModuleSlotTracker.h"
 #include "llvm/Support/InstructionCost.h"
 
 namespace llvm {
@@ -387,9 +388,14 @@ class VPSlotTracker {
   /// Number to assign to the next VPValue without underlying value.
   unsigned NextSlot = 0;
 
+  /// Lazily created ModuleSlotTracker, used only when unnamed IR instructions
+  /// require slot tracking.
+  std::unique_ptr<ModuleSlotTracker> MST;
+
   void assignName(const VPValue *V);
   void assignNames(const VPlan &Plan);
   void assignNames(const VPBasicBlock *VPBB);
+  std::string getName(const VPValue *V);
 
 public:
   VPSlotTracker(const VPlan *Plan = nullptr) {