From 808b97bd136085cf66f6b3d97b0c79170d9634d5 Mon Sep 17 00:00:00 2001 From: Igor Kirillov Date: Wed, 14 May 2025 10:57:58 +0000 Subject: [PATCH 1/3] [VPlan] Speed up VPSlotTracker by using ModuleSlotTracker MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, when VPSlotTracker is initialized with a VPlan, its assignName method calls printAsOperand on each underlying instruction. Each such call recomputes slot numbers for the entire function, leading to O(N × M) complexity, where M is the number of instructions in the loop and N is the number of instructions in the function. This results in slow debug output for large loops. For example, printing costs of all instructions becomes O(M² × N), which is especially painful when enabling verbose dumps. This patch improves debugging performance by caching slot numbers using ModuleSlotTracker. It avoids redundant recomputation and makes debug output significantly faster. --- llvm/lib/Transforms/Vectorize/VPlan.cpp | 5 ++++- llvm/lib/Transforms/Vectorize/VPlanHelpers.h | 14 +++++++++++++- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp index 165b57c87beb1..6e61ab5f551bc 100644 --- a/llvm/lib/Transforms/Vectorize/VPlan.cpp +++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp @@ -1498,7 +1498,10 @@ void VPSlotTracker::assignName(const VPValue *V) { std::string Name; if (UV) { raw_string_ostream S(Name); - UV->printAsOperand(S, false); + if (MST) + UV->printAsOperand(S, false, *MST); + else + UV->printAsOperand(S, false); } else Name = VPI->getName(); diff --git a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h index 0446991ebfff3..e2e2e18c8e4c7 100644 --- a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h +++ b/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 { @@ -387,14 +388,25 @@ class VPSlotTracker { /// Number to assign to the next VPValue without underlying value. unsigned NextSlot = 0; + /// Cache slot indexes to avoid recomputing them on each printAsOperand call. + std::unique_ptr MST; + void assignName(const VPValue *V); void assignNames(const VPlan &Plan); void assignNames(const VPBasicBlock *VPBB); public: VPSlotTracker(const VPlan *Plan = nullptr) { - if (Plan) + if (Plan) { + // This check is required to support unit tests with incomplete IR. + if (Function *F = + Plan->getScalarHeader()->getIRBasicBlock()->getParent()) { + Module *M = F->getParent(); + MST = std::make_unique(M); + MST->incorporateFunction(*F); + } assignNames(*Plan); + } } /// Returns the name assigned to \p V, if there is one, otherwise try to From 588ae00ca12a17c1f548c474b82002afac845b81 Mon Sep 17 00:00:00 2001 From: Igor Kirillov Date: Fri, 16 May 2025 10:59:06 +0000 Subject: [PATCH 2/3] Initialize MST lazily --- llvm/lib/Transforms/Vectorize/VPlan.cpp | 17 +++++++++++++++-- llvm/lib/Transforms/Vectorize/VPlanHelpers.h | 13 +++---------- 2 files changed, 18 insertions(+), 12 deletions(-) diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp index 6e61ab5f551bc..1715325f334d1 100644 --- a/llvm/lib/Transforms/Vectorize/VPlan.cpp +++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp @@ -1498,10 +1498,23 @@ void VPSlotTracker::assignName(const VPValue *V) { std::string Name; if (UV) { raw_string_ostream S(Name); - if (MST) + if (MST) { UV->printAsOperand(S, false, *MST); - else + } else if (isa(UV) && !UV->hasName()) { + // Lazily create the ModuleSlotTracker when we first hit an unnamed + // instruction + auto *IUV = cast(UV); + // This check is required to support unit tests with incomplete IR. + if (IUV->getParent()) { + MST = std::make_unique(IUV->getModule()); + MST->incorporateFunction(*IUV->getFunction()); + } else { + MST = std::make_unique(nullptr); + } + UV->printAsOperand(S, false, *MST); + } else { UV->printAsOperand(S, false); + } } else Name = VPI->getName(); diff --git a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h index e2e2e18c8e4c7..a8082b311753c 100644 --- a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h +++ b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h @@ -388,7 +388,8 @@ class VPSlotTracker { /// Number to assign to the next VPValue without underlying value. unsigned NextSlot = 0; - /// Cache slot indexes to avoid recomputing them on each printAsOperand call. + /// Lazily created ModuleSlotTracker, used only when unnamed IR instructions + /// require slot tracking. std::unique_ptr MST; void assignName(const VPValue *V); @@ -397,16 +398,8 @@ class VPSlotTracker { public: VPSlotTracker(const VPlan *Plan = nullptr) { - if (Plan) { - // This check is required to support unit tests with incomplete IR. - if (Function *F = - Plan->getScalarHeader()->getIRBasicBlock()->getParent()) { - Module *M = F->getParent(); - MST = std::make_unique(M); - MST->incorporateFunction(*F); - } + if (Plan) assignNames(*Plan); - } } /// Returns the name assigned to \p V, if there is one, otherwise try to From fc5b3328d56b44c191f52564093759cc8293396c Mon Sep 17 00:00:00 2001 From: Igor Kirillov Date: Fri, 30 May 2025 10:46:41 +0000 Subject: [PATCH 3/3] Move code a separate function --- llvm/lib/Transforms/Vectorize/VPlan.cpp | 52 +++++++++++--------- llvm/lib/Transforms/Vectorize/VPlanHelpers.h | 1 + 2 files changed, 30 insertions(+), 23 deletions(-) diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp index 1715325f334d1..d3b21a693a245 100644 --- a/llvm/lib/Transforms/Vectorize/VPlan.cpp +++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp @@ -1495,29 +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); - if (MST) { - UV->printAsOperand(S, false, *MST); - } else if (isa(UV) && !UV->hasName()) { - // Lazily create the ModuleSlotTracker when we first hit an unnamed - // instruction - auto *IUV = cast(UV); - // This check is required to support unit tests with incomplete IR. - if (IUV->getParent()) { - MST = std::make_unique(IUV->getModule()); - MST->incorporateFunction(*IUV->getFunction()); - } else { - MST = std::make_unique(nullptr); - } - UV->printAsOperand(S, false, *MST); - } else { - 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(); @@ -1562,6 +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(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(UV) && !UV->hasName()) { + // Lazily create the ModuleSlotTracker when we first hit an unnamed + // instruction + auto *IUV = cast(UV); + // This check is required to support unit tests with incomplete IR. + if (IUV->getParent()) { + MST = std::make_unique(IUV->getModule()); + MST->incorporateFunction(*IUV->getFunction()); + } else { + MST = std::make_unique(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()) diff --git a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h index a8082b311753c..2a711c3843c4a 100644 --- a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h +++ b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h @@ -395,6 +395,7 @@ class VPSlotTracker { 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) {