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[LoopSimplifyCFG] Use DTU.applyUpdates instead of insert/deleteEdge 

`insert/deleteEdge` methods in DTU can make updates incorrectly in some cases
(see https://bugs.llvm.org/show_bug.cgi?id=40528), and it is recommended to
use `applyUpdates` methods instead when it is needed to make a mass update in CFG.

Differential Revision: https://reviews.llvm.org/D57316
Reviewed By: kuhar

llvm-svn: 353502
This commit is contained in:
Max Kazantsev 2019-02-08 08:12:41 +00:00
parent 5b09834bc3
commit 6b63d3a277
2 changed files with 120 additions and 32 deletions
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33
llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
View File

@ -89,6 +89,8 @@ private:
DominatorTree &DT;
ScalarEvolution &SE;
MemorySSAUpdater *MSSAU;
DomTreeUpdater DTU;
SmallVector<DominatorTree::UpdateType, 16> DTUpdates;
// Whether or not the current loop has irreducible CFG.
bool HasIrreducibleCFG = false;
@ -319,14 +321,13 @@ private:
// Construct split preheader and the dummy switch to thread edges from it to
// dead exits.
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
BasicBlock *Preheader = L.getLoopPreheader();
BasicBlock *NewPreheader = Preheader->splitBasicBlock(
Preheader->getTerminator(),
Twine(Preheader->getName()).concat("-split"));
DTU.deleteEdge(Preheader, L.getHeader());
DTU.insertEdge(NewPreheader, L.getHeader());
DTU.insertEdge(Preheader, NewPreheader);
DTUpdates.push_back({DominatorTree::Delete, Preheader, L.getHeader()});
DTUpdates.push_back({DominatorTree::Insert, NewPreheader, L.getHeader()});
DTUpdates.push_back({DominatorTree::Insert, Preheader, NewPreheader});
IRBuilder<> Builder(Preheader->getTerminator());
SwitchInst *DummySwitch =
Builder.CreateSwitch(Builder.getInt32(0), NewPreheader);
@ -345,7 +346,7 @@ private:
}
assert(DummyIdx != 0 && "Too many dead exits!");
DummySwitch->addCase(Builder.getInt32(DummyIdx++), BB);
DTU.insertEdge(Preheader, BB);
DTUpdates.push_back({DominatorTree::Insert, Preheader, BB});
++NumLoopExitsDeleted;
}
@ -389,6 +390,9 @@ private:
while (FixLCSSALoop->getParentLoop() != StillReachable)
FixLCSSALoop = FixLCSSALoop->getParentLoop();
assert(FixLCSSALoop && "Should be a loop!");
// We need all DT updates to be done before forming LCSSA.
DTU.applyUpdates(DTUpdates);
DTUpdates.clear();
formLCSSARecursively(*FixLCSSALoop, DT, &LI, &SE);
}
}
@ -397,7 +401,6 @@ private:
/// Delete loop blocks that have become unreachable after folding. Make all
/// relevant updates to DT and LI.
void deleteDeadLoopBlocks() {
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
if (MSSAU) {
SmallPtrSet<BasicBlock *, 8> DeadLoopBlocksSet(DeadLoopBlocks.begin(),
DeadLoopBlocks.end());
@ -415,15 +418,18 @@ private:
LI.removeBlock(BB);
}
DeleteDeadBlocks(DeadLoopBlocks, &DTU);
DetatchDeadBlocks(DeadLoopBlocks, &DTUpdates);
DTU.applyUpdates(DTUpdates);
DTUpdates.clear();
for (auto *BB : DeadLoopBlocks)
BB->eraseFromParent();
NumLoopBlocksDeleted += DeadLoopBlocks.size();
}
/// Constant-fold terminators of blocks acculumated in FoldCandidates into the
/// unconditional branches.
void foldTerminators() {
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
for (BasicBlock *BB : FoldCandidates) {
assert(LI.getLoopFor(BB) == &L && "Should be a loop block!");
BasicBlock *TheOnlySucc = getOnlyLiveSuccessor(BB);
@ -465,7 +471,7 @@ private:
Term->eraseFromParent();
for (auto *DeadSucc : DeadSuccessors)
DTU.deleteEdge(BB, DeadSucc);
DTUpdates.push_back({DominatorTree::Delete, BB, DeadSucc});
++NumTerminatorsFolded;
}
@ -475,7 +481,8 @@ public:
ConstantTerminatorFoldingImpl(Loop &L, LoopInfo &LI, DominatorTree &DT,
ScalarEvolution &SE,
MemorySSAUpdater *MSSAU)
: L(L), LI(LI), DT(DT), SE(SE), MSSAU(MSSAU) {}
: L(L), LI(LI), DT(DT), SE(SE), MSSAU(MSSAU),
DTU(DT, DomTreeUpdater::UpdateStrategy::Eager) {}
bool run() {
assert(L.getLoopLatch() && "Should be single latch!");
@ -539,6 +546,10 @@ public:
<< " dead blocks in loop " << L.getHeader()->getName()
<< "\n");
deleteDeadLoopBlocks();
} else {
// If we didn't do updates inside deleteDeadLoopBlocks, do them here.
DTU.applyUpdates(DTUpdates);
DTUpdates.clear();
}
#ifndef NDEBUG

79
llvm/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
View File

@ -1,5 +1,4 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; XFAIL: *
; REQUIRES: asserts
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(simplify-cfg)' -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
@ -2582,6 +2581,84 @@ exit:
}
define void @test_crash_01() {
; CHECK-LABEL: @test_crash_01(
; CHECK-NEXT: bb:
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br i1 undef, label [[BB17:%.*]], label [[BB2:%.*]]
; CHECK: bb2:
; CHECK-NEXT: switch i32 0, label [[BB2_SPLIT:%.*]] [
; CHECK-NEXT: i32 1, label [[BB19:%.*]]
; CHECK-NEXT: ]
; CHECK: bb2-split:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb3:
; CHECK-NEXT: switch i32 undef, label [[BB16:%.*]] [
; CHECK-NEXT: i32 0, label [[BB15:%.*]]
; CHECK-NEXT: i32 1, label [[BB14:%.*]]
; CHECK-NEXT: i32 2, label [[BB13:%.*]]
; CHECK-NEXT: i32 3, label [[BB12:%.*]]
; CHECK-NEXT: i32 4, label [[BB11:%.*]]
; CHECK-NEXT: i32 5, label [[BB8:%.*]]
; CHECK-NEXT: i32 6, label [[BB10:%.*]]
; CHECK-NEXT: i32 7, label [[BB9:%.*]]
; CHECK-NEXT: i32 8, label [[BB7:%.*]]
; CHECK-NEXT: ]
; CHECK: bb7:
; CHECK-NEXT: unreachable
; CHECK: bb8:
; CHECK-NEXT: switch i32 undef, label [[BB28:%.*]] [
; CHECK-NEXT: i32 0, label [[BB27:%.*]]
; CHECK-NEXT: i32 1, label [[BB26:%.*]]
; CHECK-NEXT: i32 2, label [[BB23:%.*]]
; CHECK-NEXT: i32 3, label [[BB24:%.*]]
; CHECK-NEXT: i32 4, label [[BB25:%.*]]
; CHECK-NEXT: i32 5, label [[BB29:%.*]]
; CHECK-NEXT: i32 6, label [[BB22:%.*]]
; CHECK-NEXT: i32 7, label [[BB20:%.*]]
; CHECK-NEXT: i32 8, label [[BB21:%.*]]
; CHECK-NEXT: ]
; CHECK: bb9:
; CHECK-NEXT: unreachable
; CHECK: bb10:
; CHECK-NEXT: unreachable
; CHECK: bb11:
; CHECK-NEXT: br label [[BB8]]
; CHECK: bb12:
; CHECK-NEXT: unreachable
; CHECK: bb13:
; CHECK-NEXT: unreachable
; CHECK: bb14:
; CHECK-NEXT: unreachable
; CHECK: bb15:
; CHECK-NEXT: unreachable
; CHECK: bb16:
; CHECK-NEXT: unreachable
; CHECK: bb17:
; CHECK-NEXT: ret void
; CHECK: bb19:
; CHECK-NEXT: ret void
; CHECK: bb20:
; CHECK-NEXT: unreachable
; CHECK: bb21:
; CHECK-NEXT: unreachable
; CHECK: bb22:
; CHECK-NEXT: unreachable
; CHECK: bb23:
; CHECK-NEXT: unreachable
; CHECK: bb24:
; CHECK-NEXT: unreachable
; CHECK: bb25:
; CHECK-NEXT: unreachable
; CHECK: bb26:
; CHECK-NEXT: unreachable
; CHECK: bb27:
; CHECK-NEXT: unreachable
; CHECK: bb28:
; CHECK-NEXT: unreachable
; CHECK: bb29:
; CHECK-NEXT: br label [[BB3]]
;
bb:
br label %bb1