f175e04435
This makes RemoveDuplicatePHINodes more effective and fixes an assertion
failure. Triggering the assertions requires a DenseSet reallocation
so this change only contains a constructive test.
I'll explain the issue with a small example. In the following function
there's a duplicate PHI, %4 and %5 are identical. When this is found
the DenseSet in RemoveDuplicatePHINodes contains %2, %3 and %4.
define void @F() {
br label %1
; <label>:1 ; preds = %1, %0
%2 = phi i32 [ 42, %0 ], [ %4, %1 ]
%3 = phi i32 [ 42, %0 ], [ %5, %1 ]
%4 = phi i32 [ 42, %0 ], [ 23, %1 ]
%5 = phi i32 [ 42, %0 ], [ 23, %1 ]
br label %1
}
after RemoveDuplicatePHINodes runs the function looks like this. %3 has
changed and is now identical to %2, but RemoveDuplicatePHINodes never
saw this.
define void @F() {
br label %1
; <label>:1 ; preds = %1, %0
%2 = phi i32 [ 42, %0 ], [ %4, %1 ]
%3 = phi i32 [ 42, %0 ], [ %4, %1 ]
%4 = phi i32 [ 42, %0 ], [ 23, %1 ]
br label %1
}
If the DenseSet does a reallocation now it will reinsert all
keys and stumble over %3 now having a different hash value than it had
when inserted into the map for the first time. This change clears the
set whenever a PHI is deleted and starts the progress from the
beginning, allowing %3 to be deleted and avoiding inconsistent DenseSet
state. This potentially has a negative performance impact because
it rescans all PHIs, but I don't think that this ever makes a difference
in practice.
llvm-svn: 246694
98 lines
2.8 KiB
C++
98 lines
2.8 KiB
C++
//===- Local.cpp - Unit tests for Local -----------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "gtest/gtest.h"
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using namespace llvm;
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TEST(Local, RecursivelyDeleteDeadPHINodes) {
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LLVMContext &C(getGlobalContext());
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IRBuilder<> builder(C);
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// Make blocks
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BasicBlock *bb0 = BasicBlock::Create(C);
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BasicBlock *bb1 = BasicBlock::Create(C);
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builder.SetInsertPoint(bb0);
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PHINode *phi = builder.CreatePHI(Type::getInt32Ty(C), 2);
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BranchInst *br0 = builder.CreateCondBr(builder.getTrue(), bb0, bb1);
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builder.SetInsertPoint(bb1);
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BranchInst *br1 = builder.CreateBr(bb0);
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phi->addIncoming(phi, bb0);
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phi->addIncoming(phi, bb1);
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// The PHI will be removed
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EXPECT_TRUE(RecursivelyDeleteDeadPHINode(phi));
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// Make sure the blocks only contain the branches
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EXPECT_EQ(&bb0->front(), br0);
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EXPECT_EQ(&bb1->front(), br1);
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builder.SetInsertPoint(bb0);
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phi = builder.CreatePHI(Type::getInt32Ty(C), 0);
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EXPECT_TRUE(RecursivelyDeleteDeadPHINode(phi));
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builder.SetInsertPoint(bb0);
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phi = builder.CreatePHI(Type::getInt32Ty(C), 0);
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builder.CreateAdd(phi, phi);
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EXPECT_TRUE(RecursivelyDeleteDeadPHINode(phi));
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bb0->dropAllReferences();
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bb1->dropAllReferences();
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delete bb0;
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delete bb1;
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}
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TEST(Local, RemoveDuplicatePHINodes) {
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LLVMContext &C(getGlobalContext());
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IRBuilder<> B(C);
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std::unique_ptr<Function> F(
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Function::Create(FunctionType::get(B.getVoidTy(), false),
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GlobalValue::ExternalLinkage, "F"));
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BasicBlock *Entry(BasicBlock::Create(C, "", F.get()));
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BasicBlock *BB(BasicBlock::Create(C, "", F.get()));
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BranchInst::Create(BB, Entry);
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B.SetInsertPoint(BB);
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AssertingVH<PHINode> P1 = B.CreatePHI(Type::getInt32Ty(C), 2);
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P1->addIncoming(B.getInt32(42), Entry);
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PHINode *P2 = B.CreatePHI(Type::getInt32Ty(C), 2);
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P2->addIncoming(B.getInt32(42), Entry);
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AssertingVH<PHINode> P3 = B.CreatePHI(Type::getInt32Ty(C), 2);
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P3->addIncoming(B.getInt32(42), Entry);
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P3->addIncoming(B.getInt32(23), BB);
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PHINode *P4 = B.CreatePHI(Type::getInt32Ty(C), 2);
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P4->addIncoming(B.getInt32(42), Entry);
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P4->addIncoming(B.getInt32(23), BB);
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P1->addIncoming(P3, BB);
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P2->addIncoming(P4, BB);
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BranchInst::Create(BB, BB);
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// Verify that we can eliminate PHIs that become duplicates after chaning PHIs
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// downstream.
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EXPECT_TRUE(EliminateDuplicatePHINodes(BB));
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EXPECT_EQ(3U, BB->size());
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}
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