[llvm] [GVN] Improve processBlock for instruction erasure (PR #131753)
Madhur Amilkanthwar via llvm-commits
llvm-commits at lists.llvm.org
Tue Mar 18 01:12:58 PDT 2025
https://github.com/madhur13490 created https://github.com/llvm/llvm-project/pull/131753
This patch deletes the instructions right away by using the approapriate iterators. Thus avoids collecting the instructions in a vector and then doing the erasure.
>From 4de1a9e461fbc5d780ac89e664f09a19a88faf8c Mon Sep 17 00:00:00 2001
From: Madhur Amilkanthwar <madhura at nvidia.com>
Date: Tue, 4 Mar 2025 00:43:40 -0800
Subject: [PATCH] [GVN] Improve processBlock for instruction erasure
This patch deletes the instructions right away by using
the approapriate iterators. Thus avoids collecting the instructions
in a vector and then doing the erasure.
---
llvm/include/llvm/Transforms/Scalar/GVN.h | 9 ++--
llvm/lib/Transforms/Scalar/GVN.cpp | 62 ++++++-----------------
2 files changed, 21 insertions(+), 50 deletions(-)
diff --git a/llvm/include/llvm/Transforms/Scalar/GVN.h b/llvm/include/llvm/Transforms/Scalar/GVN.h
index c8be390799836..01b3763fb5581 100644
--- a/llvm/include/llvm/Transforms/Scalar/GVN.h
+++ b/llvm/include/llvm/Transforms/Scalar/GVN.h
@@ -25,6 +25,8 @@
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
+#include "llvm/Transforms/Utils/Local.h"
#include <cstdint>
#include <optional>
#include <utility>
@@ -137,9 +139,11 @@ class GVNPass : public PassInfoMixin<GVNPass> {
/// This removes the specified instruction from
/// our various maps and marks it for deletion.
- void markInstructionForDeletion(Instruction *I) {
+ void doInstructionDeletion(Instruction *I) {
+ salvageKnowledge(I, AC);
+ salvageDebugInfo(*I);
VN.erase(I);
- InstrsToErase.push_back(I);
+ removeInstruction(I);
}
DominatorTree &getDominatorTree() const { return *DT; }
@@ -306,7 +310,6 @@ class GVNPass : public PassInfoMixin<GVNPass> {
// propagate to any successors. Entries added mid-block are applied
// to the remaining instructions in the block.
SmallMapVector<Value *, Value *, 4> ReplaceOperandsWithMap;
- SmallVector<Instruction *, 8> InstrsToErase;
// Map the block to reversed postorder traversal number. It is used to
// find back edge easily.
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 85fcdd95f5d87..5550721f8d249 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -730,8 +730,9 @@ void GVNPass::ValueTable::erase(Value *V) {
/// verifyRemoved - Verify that the value is removed from all internal data
/// structures.
void GVNPass::ValueTable::verifyRemoved(const Value *V) const {
- assert(!valueNumbering.contains(V) &&
- "Inst still occurs in value numbering map!");
+ if (V != nullptr)
+ assert(!valueNumbering.contains(V) &&
+ "Inst still occurs in value numbering map!");
}
//===----------------------------------------------------------------------===//
@@ -1574,7 +1575,7 @@ void GVNPass::eliminatePartiallyRedundantLoad(
I->setDebugLoc(Load->getDebugLoc());
if (V->getType()->isPtrOrPtrVectorTy())
MD->invalidateCachedPointerInfo(V);
- markInstructionForDeletion(Load);
+ doInstructionDeletion(Load);
ORE->emit([&]() {
return OptimizationRemark(DEBUG_TYPE, "LoadPRE", Load)
<< "load eliminated by PRE";
@@ -1798,7 +1799,7 @@ bool GVNPass::PerformLoadPRE(LoadInst *Load, AvailValInBlkVect &ValuesPerBlock,
// Erase instructions generated by the failed PHI translation before
// trying to number them. PHI translation might insert instructions
// in basic blocks other than the current one, and we delete them
- // directly, as markInstructionForDeletion only allows removing from the
+ // directly, as doInstructionDeletion only allows removing from the
// current basic block.
NewInsts.pop_back_val()->eraseFromParent();
}
@@ -1997,7 +1998,7 @@ bool GVNPass::processNonLocalLoad(LoadInst *Load) {
I->setDebugLoc(Load->getDebugLoc());
if (V->getType()->isPtrOrPtrVectorTy())
MD->invalidateCachedPointerInfo(V);
- markInstructionForDeletion(Load);
+ doInstructionDeletion(Load);
++NumGVNLoad;
reportLoadElim(Load, V, ORE);
return true;
@@ -2067,7 +2068,7 @@ bool GVNPass::processAssumeIntrinsic(AssumeInst *IntrinsicI) {
}
}
if (isAssumeWithEmptyBundle(*IntrinsicI)) {
- markInstructionForDeletion(IntrinsicI);
+ doInstructionDeletion(IntrinsicI);
return true;
}
return false;
@@ -2179,7 +2180,7 @@ bool GVNPass::processLoad(LoadInst *L) {
return false;
if (L->use_empty()) {
- markInstructionForDeletion(L);
+ doInstructionDeletion(L);
return true;
}
@@ -2209,13 +2210,13 @@ bool GVNPass::processLoad(LoadInst *L) {
// MaterializeAdjustedValue is responsible for combining metadata.
ICF->removeUsersOf(L);
L->replaceAllUsesWith(AvailableValue);
- markInstructionForDeletion(L);
if (MSSAU)
MSSAU->removeMemoryAccess(L);
++NumGVNLoad;
reportLoadElim(L, AvailableValue, ORE);
// Tell MDA to reexamine the reused pointer since we might have more
// information after forwarding it.
+ doInstructionDeletion(L);
if (MD && AvailableValue->getType()->isPtrOrPtrVectorTy())
MD->invalidateCachedPointerInfo(AvailableValue);
return true;
@@ -2605,7 +2606,7 @@ bool GVNPass::processInstruction(Instruction *I) {
Changed = true;
}
if (isInstructionTriviallyDead(I, TLI)) {
- markInstructionForDeletion(I);
+ doInstructionDeletion(I);
Changed = true;
}
if (Changed) {
@@ -2723,7 +2724,7 @@ bool GVNPass::processInstruction(Instruction *I) {
patchAndReplaceAllUsesWith(I, Repl);
if (MD && Repl->getType()->isPtrOrPtrVectorTy())
MD->invalidateCachedPointerInfo(Repl);
- markInstructionForDeletion(I);
+ doInstructionDeletion(I);
return true;
}
@@ -2799,10 +2800,6 @@ bool GVNPass::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
}
bool GVNPass::processBlock(BasicBlock *BB) {
- // FIXME: Kill off InstrsToErase by doing erasing eagerly in a helper function
- // (and incrementing BI before processing an instruction).
- assert(InstrsToErase.empty() &&
- "We expect InstrsToErase to be empty across iterations");
if (DeadBlocks.count(BB))
return false;
@@ -2820,41 +2817,12 @@ bool GVNPass::processBlock(BasicBlock *BB) {
VN.erase(PN);
removeInstruction(PN);
}
-
- for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
- BI != BE;) {
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
+ Instruction *Inst = &*BI++;
if (!ReplaceOperandsWithMap.empty())
- ChangedFunction |= replaceOperandsForInBlockEquality(&*BI);
- ChangedFunction |= processInstruction(&*BI);
-
- if (InstrsToErase.empty()) {
- ++BI;
- continue;
- }
-
- // If we need some instructions deleted, do it now.
- NumGVNInstr += InstrsToErase.size();
-
- // Avoid iterator invalidation.
- bool AtStart = BI == BB->begin();
- if (!AtStart)
- --BI;
-
- for (auto *I : InstrsToErase) {
- assert(I->getParent() == BB && "Removing instruction from wrong block?");
- LLVM_DEBUG(dbgs() << "GVN removed: " << *I << '\n');
- salvageKnowledge(I, AC);
- salvageDebugInfo(*I);
- removeInstruction(I);
- }
- InstrsToErase.clear();
-
- if (AtStart)
- BI = BB->begin();
- else
- ++BI;
+ ChangedFunction |= replaceOperandsForInBlockEquality(Inst);
+ ChangedFunction |= processInstruction(Inst);
}
-
return ChangedFunction;
}
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