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[LCSSA] Provide option for caller to clean up unused PHIs.
formLCSSAForInstructions is used by SCEVExpander, which tracks all inserted instructions including LCSSA phis using asserting value handles. This means cleanup needs to happen in the caller. Extend formLCSSAForInstructions to take an optional pointer to a vector. If this argument is non-nullptr, instead of directly deleting the phis, add them to the vector, so the caller can process them. This should address various PPC buildbot failures, including http://lab.llvm.org:8011/builders/clang-ppc64be-linux-lnt/builds/40567
This commit is contained in:
Florian Hahn
parent
63334e0fdd
commit
a60d0184bb
@ -74,9 +74,14 @@ bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
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/// changes to CFG, preserved.
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///
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/// Returns true if any modifications are made.
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bool formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
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const DominatorTree &DT, const LoopInfo &LI,
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ScalarEvolution *SE, IRBuilderBase &Builder);
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///
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/// This function may introduce unused PHI nodes. If \p PHIsToRemove is not
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/// nullptr, those are added to it (before removing, the caller has to check if
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/// they still do not have any uses). Otherwise the PHIs are directly removed.
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bool formLCSSAForInstructions(
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SmallVectorImpl<Instruction *> &Worklist, const DominatorTree &DT,
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const LoopInfo &LI, ScalarEvolution *SE, IRBuilderBase &Builder,
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SmallVectorImpl<PHINode *> *PHIsToRemove = nullptr);
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/// Put loop into LCSSA form.
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///
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@ -78,10 +78,10 @@ static bool isExitBlock(BasicBlock *BB,
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/// rewrite the uses.
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bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
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const DominatorTree &DT, const LoopInfo &LI,
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ScalarEvolution *SE,
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IRBuilderBase &Builder) {
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ScalarEvolution *SE, IRBuilderBase &Builder,
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SmallVectorImpl<PHINode *> *PHIsToRemove) {
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SmallVector<Use *, 16> UsesToRewrite;
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SmallSetVector<PHINode *, 16> PHIsToRemove;
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SmallSetVector<PHINode *, 16> LocalPHIsToRemove;
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PredIteratorCache PredCache;
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bool Changed = false;
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@ -257,22 +257,28 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
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SmallVector<PHINode *, 2> NeedDbgValues;
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for (PHINode *PN : AddedPHIs)
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if (PN->use_empty())
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PHIsToRemove.insert(PN);
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LocalPHIsToRemove.insert(PN);
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else
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NeedDbgValues.push_back(PN);
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insertDebugValuesForPHIs(InstBB, NeedDbgValues);
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Changed = true;
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}
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// Remove PHI nodes that did not have any uses rewritten. We need to redo the
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// use_empty() check here, because even if the PHI node wasn't used when added
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// to PHIsToRemove, later added PHI nodes can be using it. This cleanup is
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// not guaranteed to handle trees/cycles of PHI nodes that only are used by
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// each other. Such situations has only been noticed when the input IR
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// contains unreachable code, and leaving some extra redundant PHI nodes in
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// such situations is considered a minor problem.
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for (PHINode *PN : PHIsToRemove)
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// Remove PHI nodes that did not have any uses rewritten or add them to
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// PHIsToRemove, so the caller can remove them after some additional cleanup.
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// We need to redo the use_empty() check here, because even if the PHI node
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// wasn't used when added to LocalPHIsToRemove, later added PHI nodes can be
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// using it. This cleanup is not guaranteed to handle trees/cycles of PHI
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// nodes that only are used by each other. Such situations has only been
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// noticed when the input IR contains unreachable code, and leaving some extra
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// redundant PHI nodes in such situations is considered a minor problem.
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if (PHIsToRemove) {
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PHIsToRemove->append(LocalPHIsToRemove.begin(), LocalPHIsToRemove.end());
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} else {
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for (PHINode *PN : LocalPHIsToRemove)
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if (PN->use_empty())
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PN->eraseFromParent();
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}
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return Changed;
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}
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@ -2537,7 +2537,16 @@ Value *SCEVExpander::fixupLCSSAFormFor(Instruction *User, unsigned OpIdx) {
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return OpV;
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ToUpdate.push_back(OpI);
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formLCSSAForInstructions(ToUpdate, SE.DT, SE.LI, &SE, Builder);
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SmallVector<PHINode *, 16> PHIsToRemove;
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formLCSSAForInstructions(ToUpdate, SE.DT, SE.LI, &SE, Builder, &PHIsToRemove);
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for (PHINode *PN : PHIsToRemove) {
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if (!PN->use_empty())
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continue;
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InsertedValues.erase(PN);
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InsertedPostIncValues.erase(PN);
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PN->eraseFromParent();
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}
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return User->getOperand(OpIdx);
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}
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101
test/CodeGen/PowerPC/hardware-loops-crash.ll
Normal file
101
test/CodeGen/PowerPC/hardware-loops-crash.ll
Normal file
@ -0,0 +1,101 @@
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -hardware-loops -S -verify-loop-lcssa | FileCheck %s
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target datalayout = "E-m:e-i64:64-n32:64"
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target triple = "ppc64-unknown-linux-elf"
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declare i1 @cond() readnone
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; Make sure we do not crash on the test.
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define void @test() {
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; CHECK-LABEL: @test(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[WHILE_COND:%.*]]
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; CHECK: while.cond:
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; CHECK-NEXT: br label [[FOR_BODY:%.*]]
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; CHECK: for.body:
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; CHECK-NEXT: br label [[FOR_INC:%.*]]
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; CHECK: for.inc:
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; CHECK-NEXT: [[C_0:%.*]] = call i1 @cond()
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; CHECK-NEXT: br i1 [[C_0]], label [[WHILE_COND25:%.*]], label [[FOR_BODY]]
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; CHECK: while.cond25:
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; CHECK-NEXT: [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], [[LAND_RHS:%.*]] ], [ 0, [[FOR_INC]] ]
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; CHECK-NEXT: [[INDVARS_IV349:%.*]] = phi i64 [ [[INDVARS_IV_NEXT350:%.*]], [[LAND_RHS]] ], [ 50, [[FOR_INC]] ]
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; CHECK-NEXT: [[CMP26_NOT:%.*]] = icmp eq i64 [[INDVARS_IV349]], 0
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; CHECK-NEXT: br i1 [[CMP26_NOT]], label [[WHILE_END187:%.*]], label [[LAND_RHS]]
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; CHECK: land.rhs:
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; CHECK-NEXT: [[INDVARS_IV_NEXT350]] = add nsw i64 [[INDVARS_IV349]], -1
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; CHECK-NEXT: [[C_1:%.*]] = call i1 @cond()
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; CHECK-NEXT: [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
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; CHECK-NEXT: br i1 [[C_1]], label [[WHILE_COND25]], label [[WHILE_END:%.*]]
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; CHECK: while.end:
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; CHECK-NEXT: [[INDVAR_LCSSA1:%.*]] = phi i64 [ [[INDVAR]], [[LAND_RHS]] ]
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; CHECK-NEXT: [[C_2:%.*]] = call i1 @cond()
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; CHECK-NEXT: br i1 [[C_2]], label [[WHILE_END187]], label [[WHILE_COND35_PREHEADER:%.*]]
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; CHECK: while.cond35.preheader:
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; CHECK-NEXT: [[TMP0:%.*]] = mul nsw i64 [[INDVAR_LCSSA1]], -1
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; CHECK-NEXT: [[TMP1:%.*]] = add i64 [[TMP0]], 51
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; CHECK-NEXT: call void @llvm.set.loop.iterations.i64(i64 [[TMP1]])
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; CHECK-NEXT: br label [[WHILE_COND35:%.*]]
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; CHECK: while.cond35:
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; CHECK-NEXT: [[TMP2:%.*]] = call i1 @llvm.loop.decrement.i64(i64 1)
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; CHECK-NEXT: br i1 [[TMP2]], label [[LAND_RHS37:%.*]], label [[IF_END51:%.*]]
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; CHECK: land.rhs37:
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; CHECK-NEXT: br label [[WHILE_COND35]]
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; CHECK: if.end51:
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; CHECK-NEXT: br label [[WHILE_COND_BACKEDGE:%.*]]
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; CHECK: while.cond.backedge:
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; CHECK-NEXT: br label [[WHILE_COND]]
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; CHECK: while.end187:
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; CHECK-NEXT: ret void
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;
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entry:
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br label %while.cond
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while.cond: ; preds = %while.cond.backedge, %entry
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br label %for.body
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for.body: ; preds = %for.inc, %while.cond
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br label %for.inc
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for.inc: ; preds = %for.body
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%c.0 = call i1 @cond()
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br i1 %c.0, label %while.cond25, label %for.body
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while.cond25: ; preds = %land.rhs, %for.inc
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%indvars.iv349 = phi i64 [ %indvars.iv.next350, %land.rhs ], [ 50, %for.inc ]
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%cmp26.not = icmp eq i64 %indvars.iv349, 0
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br i1 %cmp26.not, label %while.end187, label %land.rhs
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land.rhs: ; preds = %while.cond25
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%indvars.iv.next350 = add nsw i64 %indvars.iv349, -1
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%c.1 = call i1 @cond()
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br i1 %c.1, label %while.cond25, label %while.end
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while.end: ; preds = %land.rhs
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%c.2 = call i1 @cond()
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br i1 %c.2, label %while.end187, label %while.cond35.preheader
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while.cond35.preheader: ; preds = %while.end
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%0 = and i64 %indvars.iv349, 4294967295
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br label %while.cond35
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while.cond35: ; preds = %land.rhs37, %while.cond35.preheader
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%indvars.iv351 = phi i64 [ %0, %while.cond35.preheader ], [ %indvars.iv.next352, %land.rhs37 ]
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%cmp36 = icmp sgt i64 %indvars.iv351, 0
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br i1 %cmp36, label %land.rhs37, label %if.end51
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land.rhs37: ; preds = %while.cond35
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%indvars.iv.next352 = add nsw i64 %indvars.iv351, -1
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br label %while.cond35
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if.end51: ; preds = %while.cond35
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br label %while.cond.backedge
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while.cond.backedge: ; preds = %if.end51
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br label %while.cond
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while.end187: ; preds = %while.end, %while.cond25
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ret void
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}
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