[SSAUpdaterBulk] Add PHI simplification pass. #150936
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vpykhtin
changed the title
You can test this locally with the following command:git-clang-format --diff origin/main HEAD --extensions cpp,h -- llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
View the diff from clang-format here.diff --git a/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp b/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
index 716f5f213..adeb7c143 100644
--- a/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
+++ b/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
@@ -425,20 +425,21 @@ TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_OrderExisting) {
%u = add i32 %np0, %np1
ret void
}
- )", [](BasicBlock &BB, auto *ENDPN) {
- AssertingVH<PHINode> EP0 = getPhi(BB, 2);
- AssertingVH<PHINode> EP1 = getPhi(BB, 3);
- EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
- // Expected:
- // %ep0 = phi i32 [ 1, %entry ]
- // %ep1 = phi i32 [ 1, %entry ]
- // %u = add i32 %ep0, %ep0
- EXPECT_EQ(getNumPHIs(BB), 2);
- Instruction &Add = *BB.getFirstNonPHIIt();
- EXPECT_EQ(Add.getOperand(0), EP0);
- EXPECT_EQ(Add.getOperand(1), EP0);
- (void)EP1; // Avoid "unused" warning.
- });
+ )",
+ [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ]
+ // %ep1 = phi i32 [ 1, %entry ]
+ // %u = add i32 %ep0, %ep0
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP0);
+ (void)EP1; // Avoid "unused" warning.
+ });
}
TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_OrderNew) {
@@ -454,23 +455,24 @@ TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_OrderNew) {
%u = add i32 %np0, %np1
ret void
}
- )", [](BasicBlock &BB, auto *ENDPN) {
- AssertingVH<PHINode> NP0 = getPhi(BB, 0);
- AssertingVH<PHINode> EP0 = getPhi(BB, 2);
- AssertingVH<PHINode> EP1 = getPhi(BB, 3);
- EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
- // Expected:
- // %np0 = phi i32 [ 1, %entry ]
- // %ep0 = phi i32 [ 2, %entry ]
- // %ep1 = phi i32 [ 2, %entry ]
- // %u = add i32 %np0, %np0
- EXPECT_EQ(getNumPHIs(BB), 3);
- Instruction &Add = *BB.getFirstNonPHIIt();
- EXPECT_EQ(Add.getOperand(0), NP0);
- EXPECT_EQ(Add.getOperand(1), NP0);
- (void)EP0;
- (void)EP1; // Avoid "unused" warning.
- });
+ )",
+ [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> NP0 = getPhi(BB, 0);
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %np0 = phi i32 [ 1, %entry ]
+ // %ep0 = phi i32 [ 2, %entry ]
+ // %ep1 = phi i32 [ 2, %entry ]
+ // %u = add i32 %np0, %np0
+ EXPECT_EQ(getNumPHIs(BB), 3);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), NP0);
+ EXPECT_EQ(Add.getOperand(1), NP0);
+ (void)EP0;
+ (void)EP1; // Avoid "unused" warning.
+ });
}
TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_NewRefExisting) {
@@ -486,19 +488,21 @@ TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_NewRefExisting) {
%u = add i32 %np0, %np1
br label %testbb
}
- )", [](BasicBlock &BB, auto *ENDPN) {
- AssertingVH<PHINode> EP0 = getPhi(BB, 2);
- AssertingVH<PHINode> EP1 = getPhi(BB, 3);
- EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
- // Expected:
- // %ep0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
- // %ep1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
- // %u = add i32 %ep0, %ep1
- EXPECT_EQ(getNumPHIs(BB), 2);
- Instruction &Add = *BB.getFirstNonPHIIt();
- EXPECT_EQ(Add.getOperand(0), EP0);
- EXPECT_EQ(Add.getOperand(1), EP1);
- });
+ )",
+ [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ], [ %ep0,
+ // %testbb ] %ep1 = phi i32 [ 1, %entry ],
+ // [ %ep1, %testbb ] %u = add i32 %ep0,
+ // %ep1
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP1);
+ });
}
TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_ExistingRefNew) {
@@ -514,17 +518,19 @@ TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_ExistingRefNew) {
%u = add i32 %np0, %np1
br label %testbb
}
- )", [](BasicBlock &BB, auto *ENDPN) {
- AssertingVH<PHINode> EP0 = getPhi(BB, 2);
- AssertingVH<PHINode> EP1 = getPhi(BB, 3);
- EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
- // Expected:
- // %ep0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
- // %ep1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
- // %u = add i32 %ep0, %ep1
- EXPECT_EQ(getNumPHIs(BB), 2);
- Instruction &Add = *BB.getFirstNonPHIIt();
- EXPECT_EQ(Add.getOperand(0), EP0);
- EXPECT_EQ(Add.getOperand(1), EP1);
- });
+ )",
+ [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ], [ %ep0,
+ // %testbb ] %ep1 = phi i32 [ 1, %entry ],
+ // [ %ep1, %testbb ] %u = add i32 %ep0,
+ // %ep1
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP1);
+ });
}
|
|
@llvm/pr-subscribers-llvm-transforms Author: Valery Pykhtin (vpykhtin) ChangesThis is a replacement PR for #132004 and PR llvm/llvm-project #135180. I had to recreate the PR because removed parent PR. As per discussion with @nikic, moved N2 version of EliminateNewDuplicatePHINodes into SSAUpdaterBulk class to keep things simple. Full diff: https://github.com/llvm/llvm-project/pull/150936.diff 3 Files Affected:
diff --git a/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h b/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h
index 48e8c86f7d873..2db3f6d45908f 100644
--- a/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h
+++ b/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h
@@ -13,7 +13,6 @@
#ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
#define LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
-#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/PredIteratorCache.h"
#include "llvm/Support/Compiler.h"
@@ -79,6 +78,10 @@ class SSAUpdaterBulk {
LLVM_ABI void
RewriteAllUses(DominatorTree *DT,
SmallVectorImpl<PHINode *> *InsertedPHIs = nullptr);
+
+ /// Rewrite all uses and simplify the inserted PHI nodes.
+ /// Use this method to preserve behavior when replacing SSAUpdater.
+ void RewriteAndOptimizeAllUses(DominatorTree &DT);
};
} // end namespace llvm
diff --git a/llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp b/llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp
index d7bf791a23edf..15783ccdf0a98 100644
--- a/llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp
+++ b/llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp
@@ -11,11 +11,11 @@
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/SSAUpdaterBulk.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/IteratedDominanceFrontier.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/Instructions.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/Value.h"
@@ -222,3 +222,95 @@ void SSAUpdaterBulk::RewriteAllUses(DominatorTree *DT,
}
}
}
+
+// Perform a single pass of simplification over the worklist of PHIs.
+static void simplifyPass(MutableArrayRef<PHINode *> Worklist,
+ const DataLayout &DL) {
+ for (PHINode *&PHI : Worklist) {
+ if (Value *Simplified = simplifyInstruction(PHI, DL)) {
+ PHI->replaceAllUsesWith(Simplified);
+ PHI->eraseFromParent();
+ PHI = nullptr; // Mark as removed.
+ }
+ }
+}
+
+#ifndef NDEBUG // Should this be under EXPENSIVE_CHECKS?
+// New PHI nodes should not reference one another but they may reference
+// themselves or existing PHI nodes, and existing PHI nodes may reference new
+// PHI nodes.
+static bool
+PHIAreRefEachOther(const iterator_range<BasicBlock::phi_iterator> &NewPHIs) {
+ SmallPtrSet<PHINode *, 8> NewPHISet;
+ for (PHINode &PN : NewPHIs)
+ NewPHISet.insert(&PN);
+ for (PHINode &PHI : NewPHIs) {
+ for (Value *V : PHI.incoming_values()) {
+ PHINode *IncPHI = dyn_cast<PHINode>(V);
+ if (IncPHI && IncPHI != &PHI && NewPHISet.contains(IncPHI))
+ return true;
+ }
+ }
+ return false;
+}
+#endif
+
+bool
+EliminateNewDuplicatePHINodes(BasicBlock *BB,
+ BasicBlock::phi_iterator FirstExistingPN) {
+
+ auto NewPHIs = make_range(BB->phis().begin(), FirstExistingPN);
+ assert(!PHIAreRefEachOther(NewPHIs));
+
+ auto ReplaceIfIdentical = [](PHINode &PHI, PHINode &ReplPHI) {
+ if (!PHI.isIdenticalToWhenDefined(&ReplPHI))
+ return false;
+ PHI.replaceAllUsesWith(&ReplPHI);
+ PHI.eraseFromParent();
+ return true;
+ };
+
+ // Deduplicate new PHIs first to reduce the number of comparisons on the
+ // following new -> existing pass.
+ bool Changed = false;
+ for (auto I = BB->phis().begin(); I != FirstExistingPN; ++I) {
+ for (auto J = std::next(I); J != FirstExistingPN;) {
+ Changed |= ReplaceIfIdentical(*J++, *I);
+ }
+ }
+
+ // Iterate over existing PHIs and replace identical new PHIs.
+ for (PHINode &ExistingPHI : make_range(FirstExistingPN, BB->phis().end())) {
+ auto I = BB->phis().begin();
+ assert(I != FirstExistingPN); // Should be at least one new PHI.
+ do {
+ Changed |= ReplaceIfIdentical(*I++, ExistingPHI);
+ } while (I != FirstExistingPN);
+ if (BB->phis().begin() == FirstExistingPN)
+ return Changed;
+ }
+ return Changed;
+}
+
+static void deduplicatePass(ArrayRef<PHINode *> Worklist) {
+ SmallDenseMap<BasicBlock *, unsigned> BBs;
+ for (PHINode *PHI : Worklist) {
+ if (PHI)
+ ++BBs[PHI->getParent()];
+ }
+
+ for (auto [BB, NumNewPHIs] : BBs) {
+ auto FirstExistingPN = std::next(BB->phis().begin(), NumNewPHIs);
+ EliminateNewDuplicatePHINodes(BB, FirstExistingPN);
+ }
+}
+
+void SSAUpdaterBulk::RewriteAndOptimizeAllUses(DominatorTree &DT) {
+ SmallVector<PHINode *, 4> PHIs;
+ RewriteAllUses(&DT, &PHIs);
+ if (PHIs.empty())
+ return;
+
+ simplifyPass(PHIs, PHIs.front()->getParent()->getDataLayout());
+ deduplicatePass(PHIs);
+}
diff --git a/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp b/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
index 841f44cf6bfed..db96593c1ee5b 100644
--- a/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
+++ b/llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp
@@ -308,3 +308,223 @@ TEST(SSAUpdaterBulk, TwoBBLoop) {
EXPECT_EQ(Phi->getIncomingValueForBlock(Entry), ConstantInt::get(I32Ty, 0));
EXPECT_EQ(Phi->getIncomingValueForBlock(Loop), I);
}
+
+TEST(SSAUpdaterBulk, SimplifyPHIs) {
+ const char *IR = R"(
+ define void @main(i32 %val, i1 %cond) {
+ entry:
+ br i1 %cond, label %left, label %right
+ left:
+ %add = add i32 %val, 1
+ br label %exit
+ right:
+ %sub = sub i32 %val, 1
+ br label %exit
+ exit:
+ %phi = phi i32 [ %sub, %right ], [ %add, %left ]
+ %cmp = icmp slt i32 0, 42
+ ret void
+ }
+ )";
+
+ llvm::LLVMContext Context;
+ llvm::SMDiagnostic Err;
+ std::unique_ptr<llvm::Module> M = llvm::parseAssemblyString(IR, Err, Context);
+ ASSERT_NE(M, nullptr) << "Failed to parse IR: " << Err.getMessage();
+
+ Function *F = M->getFunction("main");
+ auto *Entry = &F->getEntryBlock();
+ auto *Left = Entry->getTerminator()->getSuccessor(0);
+ auto *Right = Entry->getTerminator()->getSuccessor(1);
+ auto *Exit = Left->getSingleSuccessor();
+ auto *Val = &*F->arg_begin();
+ auto *Phi = &Exit->front();
+ auto *Cmp = &*std::next(Exit->begin());
+ auto *Add = &Left->front();
+ auto *Sub = &Right->front();
+
+ SSAUpdaterBulk Updater;
+ Type *I32Ty = Type::getInt32Ty(Context);
+
+ // Use %val directly instead of creating a phi.
+ unsigned ValVar = Updater.AddVariable("Val", I32Ty);
+ Updater.AddAvailableValue(ValVar, Left, Val);
+ Updater.AddAvailableValue(ValVar, Right, Val);
+ Updater.AddUse(ValVar, &Cmp->getOperandUse(0));
+
+ // Use existing %phi for %add and %sub values.
+ unsigned AddSubVar = Updater.AddVariable("AddSub", I32Ty);
+ Updater.AddAvailableValue(AddSubVar, Left, Add);
+ Updater.AddAvailableValue(AddSubVar, Right, Sub);
+ Updater.AddUse(AddSubVar, &Cmp->getOperandUse(1));
+
+ auto ExitSizeBefore = Exit->size();
+ DominatorTree DT(*F);
+ Updater.RewriteAndOptimizeAllUses(DT);
+
+ // Output for Exit->dump():
+ // exit: ; preds = %right, %left
+ // %phi = phi i32 [ %sub, %right ], [ %add, %left ]
+ // %cmp = icmp slt i32 %val, %phi
+ // ret void
+
+ ASSERT_EQ(Exit->size(), ExitSizeBefore);
+ ASSERT_EQ(&Exit->front(), Phi);
+ EXPECT_EQ(Val, Cmp->getOperand(0));
+ EXPECT_EQ(Phi, Cmp->getOperand(1));
+}
+
+bool EliminateNewDuplicatePHINodes(BasicBlock *BB,
+ BasicBlock::phi_iterator FirstExistingPN);
+
+// Helper to run both versions on the same input.
+static void RunEliminateNewDuplicatePHINode(
+ const char *AsmText,
+ std::function<void(BasicBlock &,
+ bool(BasicBlock *BB, BasicBlock::phi_iterator))>
+ Check) {
+ LLVMContext C;
+
+ SMDiagnostic Err;
+ std::unique_ptr<Module> M = parseAssemblyString(AsmText, Err, C);
+ if (!M) {
+ Err.print("UtilsTests", errs());
+ return;
+ }
+
+ Function *F = M->getFunction("main");
+ auto BBIt = std::find_if(F->begin(), F->end(), [](const BasicBlock &Block) {
+ return Block.getName() == "testbb";
+ });
+ ASSERT_NE(BBIt, F->end());
+ Check(*BBIt, EliminateNewDuplicatePHINodes);
+}
+
+static BasicBlock::phi_iterator getPhiIt(BasicBlock &BB, unsigned Idx) {
+ return std::next(BB.phis().begin(), Idx);
+}
+
+static PHINode *getPhi(BasicBlock &BB, unsigned Idx) {
+ return &*getPhiIt(BB, Idx);
+}
+
+static int getNumPHIs(BasicBlock &BB) {
+ return std::distance(BB.phis().begin(), BB.phis().end());
+}
+
+TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_OrderExisting) {
+ RunEliminateNewDuplicatePHINode(R"(
+ define void @main() {
+ entry:
+ br label %testbb
+ testbb:
+ %np0 = phi i32 [ 1, %entry ]
+ %np1 = phi i32 [ 1, %entry ]
+ %ep0 = phi i32 [ 1, %entry ]
+ %ep1 = phi i32 [ 1, %entry ]
+ %u = add i32 %np0, %np1
+ ret void
+ }
+ )", [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ]
+ // %ep1 = phi i32 [ 1, %entry ]
+ // %u = add i32 %ep0, %ep0
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP0);
+ (void)EP1; // Avoid "unused" warning.
+ });
+}
+
+TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_OrderNew) {
+ RunEliminateNewDuplicatePHINode(R"(
+ define void @main() {
+ entry:
+ br label %testbb
+ testbb:
+ %np0 = phi i32 [ 1, %entry ]
+ %np1 = phi i32 [ 1, %entry ]
+ %ep0 = phi i32 [ 2, %entry ]
+ %ep1 = phi i32 [ 2, %entry ]
+ %u = add i32 %np0, %np1
+ ret void
+ }
+ )", [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> NP0 = getPhi(BB, 0);
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %np0 = phi i32 [ 1, %entry ]
+ // %ep0 = phi i32 [ 2, %entry ]
+ // %ep1 = phi i32 [ 2, %entry ]
+ // %u = add i32 %np0, %np0
+ EXPECT_EQ(getNumPHIs(BB), 3);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), NP0);
+ EXPECT_EQ(Add.getOperand(1), NP0);
+ (void)EP0;
+ (void)EP1; // Avoid "unused" warning.
+ });
+}
+
+TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_NewRefExisting) {
+ RunEliminateNewDuplicatePHINode(R"(
+ define void @main() {
+ entry:
+ br label %testbb
+ testbb:
+ %np0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
+ %np1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
+ %ep0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
+ %ep1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
+ %u = add i32 %np0, %np1
+ br label %testbb
+ }
+ )", [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
+ // %ep1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
+ // %u = add i32 %ep0, %ep1
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP1);
+ });
+}
+
+TEST(SSAUpdaterBulk, EliminateNewDuplicatePHINodes_ExistingRefNew) {
+ RunEliminateNewDuplicatePHINode(R"(
+ define void @main() {
+ entry:
+ br label %testbb
+ testbb:
+ %np0 = phi i32 [ 1, %entry ], [ %np0, %testbb ]
+ %np1 = phi i32 [ 1, %entry ], [ %np1, %testbb ]
+ %ep0 = phi i32 [ 1, %entry ], [ %np0, %testbb ]
+ %ep1 = phi i32 [ 1, %entry ], [ %np1, %testbb ]
+ %u = add i32 %np0, %np1
+ br label %testbb
+ }
+ )", [](BasicBlock &BB, auto *ENDPN) {
+ AssertingVH<PHINode> EP0 = getPhi(BB, 2);
+ AssertingVH<PHINode> EP1 = getPhi(BB, 3);
+ EXPECT_TRUE(ENDPN(&BB, getPhiIt(BB, 2)));
+ // Expected:
+ // %ep0 = phi i32 [ 1, %entry ], [ %ep0, %testbb ]
+ // %ep1 = phi i32 [ 1, %entry ], [ %ep1, %testbb ]
+ // %u = add i32 %ep0, %ep1
+ EXPECT_EQ(getNumPHIs(BB), 2);
+ Instruction &Add = *BB.getFirstNonPHIIt();
+ EXPECT_EQ(Add.getOperand(0), EP0);
+ EXPECT_EQ(Add.getOperand(1), EP1);
+ });
+}
\ No newline at end of file
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This optimization is performed as a separate pass over newly inserted PHI nodes to simplify and deduplicate them. By processing PHIs separately, we avoid the complexity of tracking reference bookkeeping needed to update BBValueInfo structures during insertion.
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This is a replacement PR for #132004 and PR llvm/llvm-project #135180. I had to recreate the PR because removed parent PR.
As per discussion with @nikic, moved N2 version of EliminateNewDuplicatePHINodes into SSAUpdaterBulk class to keep things simple.