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-rw-r--r--llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h5
-rw-r--r--llvm/lib/Transforms/Utils/SSAUpdaterBulk.cpp93
-rw-r--r--llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp220
3 files changed, 316 insertions, 2 deletions
diff --git a/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h b/llvm/include/llvm/Transforms/Utils/SSAUpdaterBulk.h
index 48e8c86..2db3f6d4 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 @@ public:
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 d7bf791..9e25b98 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 +222,94 @@ 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 841f44c..79631b4 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
generated by cgit v1.1 at 2025-09-27 07:30:08 +0000