[llvm] r306252 - Revert "[LoopSimplify] Factor the logic to form dedicated exits into a utility."
Daniel Jasper via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 25 23:07:16 PDT 2017
Sure thing. Sorry about that.
On Mon, Jun 26, 2017 at 12:33 AM, Chandler Carruth <chandlerc at gmail.com>
wrote:
> When reverting, please mention the revision being reverted rather than
> just the subject. That makes it *much* easier to find reverts.
>
> On Sun, Jun 25, 2017 at 10:58 AM Daniel Jasper via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: djasper
>> Date: Sun Jun 25 10:58:25 2017
>> New Revision: 306252
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=306252&view=rev
>> Log:
>> Revert "[LoopSimplify] Factor the logic to form dedicated exits into a
>> utility."
>>
>> This leads to a segfault. Chandler already has a test case and should be
>> able to recommit with a fix soon.
>>
>> Modified:
>> llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
>> llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp
>> llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-
>> TwoSwitches-Threshold.ll
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
>>
>> Modified: llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/
>> llvm/Transforms/Utils/LoopUtils.h?rev=306252&r1=
>> 306251&r2=306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h (original)
>> +++ llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h Sun Jun 25
>> 10:58:25 2017
>> @@ -362,14 +362,6 @@ private:
>> BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo
>> *LI,
>> bool PreserveLCSSA);
>>
>> -/// Ensure that all exit blocks of the loop are dedicated exits.
>> -///
>> -/// For any loop exit block with non-loop predecessors, we split the loop
>> -/// predecessors to use a dedicated loop exit block. We update the
>> dominator
>> -/// tree and loop info if provided, and will preserve LCSSA if requested.
>> -bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
>> - bool PreserveLCSSA);
>> -
>> /// Ensures LCSSA form for every instruction from the Worklist in the
>> scope of
>> /// innermost containing loop.
>> ///
>>
>> Modified: llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
>> Transforms/Utils/LoopSimplify.cpp?rev=306252&r1=306251&r2=
>> 306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp Sun Jun 25 10:58:25
>> 2017
>> @@ -72,6 +72,7 @@ using namespace llvm;
>>
>> #define DEBUG_TYPE "loop-simplify"
>>
>> +STATISTIC(NumInserted, "Number of pre-header or exit blocks inserted");
>> STATISTIC(NumNested , "Number of nested loops split out");
>>
>> // If the block isn't already, move the new block to right after some
>> 'outside
>> @@ -151,6 +152,37 @@ BasicBlock *llvm::InsertPreheaderForLoop
>> return PreheaderBB;
>> }
>>
>> +/// \brief Ensure that the loop preheader dominates all exit blocks.
>> +///
>> +/// This method is used to split exit blocks that have predecessors
>> outside of
>> +/// the loop.
>> +static BasicBlock *rewriteLoopExitBlock(Loop *L, BasicBlock *Exit,
>> + DominatorTree *DT, LoopInfo *LI,
>> + bool PreserveLCSSA) {
>> + SmallVector<BasicBlock*, 8> LoopBlocks;
>> + for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E;
>> ++I) {
>> + BasicBlock *P = *I;
>> + if (L->contains(P)) {
>> + // Don't do this if the loop is exited via an indirect branch.
>> + if (isa<IndirectBrInst>(P->getTerminator())) return nullptr;
>> +
>> + LoopBlocks.push_back(P);
>> + }
>> + }
>> +
>> + assert(!LoopBlocks.empty() && "No edges coming in from outside the
>> loop?");
>> + BasicBlock *NewExitBB = nullptr;
>> +
>> + NewExitBB = SplitBlockPredecessors(Exit, LoopBlocks, ".loopexit", DT,
>> LI,
>> + PreserveLCSSA);
>> + if (!NewExitBB)
>> + return nullptr;
>> +
>> + DEBUG(dbgs() << "LoopSimplify: Creating dedicated exit block "
>> + << NewExitBB->getName() << "\n");
>> + return NewExitBB;
>> +}
>> +
>> /// Add the specified block, and all of its predecessors, to the
>> specified set,
>> /// if it's not already in there. Stop predecessor traversal when we
>> reach
>> /// StopBlock.
>> @@ -314,7 +346,16 @@ static Loop *separateNestedLoop(Loop *L,
>>
>> // Split edges to exit blocks from the inner loop, if they emerged in
>> the
>> // process of separating the outer one.
>> - formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
>> + SmallVector<BasicBlock *, 8> ExitBlocks;
>> + L->getExitBlocks(ExitBlocks);
>> + SmallSetVector<BasicBlock *, 8> ExitBlockSet(ExitBlocks.begin(),
>> + ExitBlocks.end());
>> + for (BasicBlock *ExitBlock : ExitBlockSet) {
>> + if (any_of(predecessors(ExitBlock),
>> + [L](BasicBlock *BB) { return !L->contains(BB); })) {
>> + rewriteLoopExitBlock(L, ExitBlock, DT, LI, PreserveLCSSA);
>> + }
>> + }
>>
>> if (PreserveLCSSA) {
>> // Fix LCSSA form for L. Some values, which previously were only
>> used inside
>> @@ -522,16 +563,29 @@ ReprocessLoop:
>> BasicBlock *Preheader = L->getLoopPreheader();
>> if (!Preheader) {
>> Preheader = InsertPreheaderForLoop(L, DT, LI, PreserveLCSSA);
>> - if (Preheader)
>> + if (Preheader) {
>> + ++NumInserted;
>> Changed = true;
>> + }
>> }
>>
>> // Next, check to make sure that all exit nodes of the loop only have
>> // predecessors that are inside of the loop. This check guarantees
>> that the
>> // loop preheader/header will dominate the exit blocks. If the exit
>> block has
>> // predecessors from outside of the loop, split the edge now.
>> - if (formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA))
>> - Changed = true;
>> + SmallVector<BasicBlock*, 8> ExitBlocks;
>> + L->getExitBlocks(ExitBlocks);
>> +
>> + SmallSetVector<BasicBlock *, 8> ExitBlockSet(ExitBlocks.begin(),
>> + ExitBlocks.end());
>> + for (BasicBlock *ExitBlock : ExitBlockSet) {
>> + if (any_of(predecessors(ExitBlock),
>> + [L](BasicBlock *BB) { return !L->contains(BB); })) {
>> + rewriteLoopExitBlock(L, ExitBlock, DT, LI, PreserveLCSSA);
>> + ++NumInserted;
>> + Changed = true;
>> + }
>> + }
>>
>> // If the header has more than two predecessors at this point (from the
>> // preheader and from multiple backedges), we must adjust the loop.
>> @@ -560,8 +614,10 @@ ReprocessLoop:
>> // insert a new block that all backedges target, then make it jump
>> to the
>> // loop header.
>> LoopLatch = insertUniqueBackedgeBlock(L, Preheader, DT, LI);
>> - if (LoopLatch)
>> + if (LoopLatch) {
>> + ++NumInserted;
>> Changed = true;
>> + }
>> }
>>
>> const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
>> @@ -589,22 +645,7 @@ ReprocessLoop:
>> // loop-invariant instructions out of the way to open up more
>> // opportunities, and the disadvantage of having the responsibility
>> // to preserve dominator information.
>> - auto HasUniqueExitBlock = [&]() {
>> - BasicBlock *UniqueExit = nullptr;
>> - for (auto *ExitingBB : ExitingBlocks)
>> - for (auto *SuccBB : successors(ExitingBB)) {
>> - if (L->contains(SuccBB))
>> - continue;
>> -
>> - if (!UniqueExit)
>> - UniqueExit = SuccBB;
>> - else if (UniqueExit != SuccBB)
>> - return false;
>> - }
>> -
>> - return true;
>> - };
>> - if (HasUniqueExitBlock()) {
>> + if (ExitBlockSet.size() == 1) {
>> for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
>> BasicBlock *ExitingBlock = ExitingBlocks[i];
>> if (!ExitingBlock->getSinglePredecessor()) continue;
>>
>> Modified: llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
>> Transforms/Utils/LoopUtils.cpp?rev=306252&r1=306251&r2=306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp Sun Jun 25 10:58:25
>> 2017
>> @@ -29,7 +29,6 @@
>> #include "llvm/IR/ValueHandle.h"
>> #include "llvm/Pass.h"
>> #include "llvm/Support/Debug.h"
>> -#include "llvm/Transforms/Utils/BasicBlockUtils.h"
>>
>> using namespace llvm;
>> using namespace llvm::PatternMatch;
>> @@ -923,67 +922,6 @@ bool InductionDescriptor::isInductionPHI
>> return true;
>> }
>>
>> -bool llvm::formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo
>> *LI,
>> - bool PreserveLCSSA) {
>> - bool Changed = false;
>> -
>> - // We re-use a vector for the in-loop predecesosrs.
>> - SmallVector<BasicBlock *, 4> InLoopPredecessors;
>> -
>> - auto RewriteExit = [&](BasicBlock *BB) {
>> - // See if there are any non-loop predecessors of this exit block and
>> - // keep track of the in-loop predecessors.
>> - bool IsDedicatedExit = true;
>> - for (auto *PredBB : predecessors(BB))
>> - if (L->contains(PredBB)) {
>> - if (isa<IndirectBrInst>(PredBB->getTerminator()))
>> - // We cannot rewrite exiting edges from an indirectbr.
>> - return false;
>> -
>> - InLoopPredecessors.push_back(PredBB);
>> - } else {
>> - IsDedicatedExit = false;
>> - }
>> -
>> - // Nothing to do if this is already a dedicated exit.
>> - if (IsDedicatedExit) {
>> - InLoopPredecessors.clear();
>> - return false;
>> - }
>> -
>> - assert(!InLoopPredecessors.empty() && "Must have *some* loop
>> predecessor!");
>> - auto *NewExitBB = SplitBlockPredecessors(
>> - BB, InLoopPredecessors, ".loopexit", DT, LI, PreserveLCSSA);
>> -
>> - if (!NewExitBB)
>> - DEBUG(dbgs() << "WARNING: Can't create a dedicated exit block for
>> loop: "
>> - << *L << "\n");
>> - else
>> - DEBUG(dbgs() << "LoopSimplify: Creating dedicated exit block "
>> - << NewExitBB->getName() << "\n");
>> - InLoopPredecessors.clear();
>> - return true;
>> - };
>> -
>> - // Walk the exit blocks directly rather than building up a data
>> structure for
>> - // them, but only visit each one once.
>> - SmallPtrSet<BasicBlock *, 4> Visited;
>> - for (auto *BB : L->blocks())
>> - for (auto *SuccBB : successors(BB)) {
>> - // We're looking for exit blocks so skip in-loop successors.
>> - if (L->contains(SuccBB))
>> - continue;
>> -
>> - // Visit each exit block exactly once.
>> - if (!Visited.insert(SuccBB).second)
>> - continue;
>> -
>> - Changed |= RewriteExit(SuccBB);
>> - }
>> -
>> - return Changed;
>> -}
>> -
>> /// \brief Returns the instructions that use values defined in the loop.
>> SmallVector<Instruction *, 8> llvm::findDefsUsedOutsideOfLoop(Loop *L) {
>> SmallVector<Instruction *, 8> UsedOutside;
>>
>> Modified: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-
>> SimpleSwitch.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
>> Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll?rev=
>> 306252&r1=306251&r2=306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
>> (original)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
>> Sun Jun 25 10:58:25 2017
>> @@ -2,6 +2,7 @@
>> ; RUN: opt -loop-unswitch -disable-output -stats -info-output-file - <
>> %s | FileCheck --check-prefix=STATS %s
>> ; RUN: opt -S -loop-unswitch -verify-loop-info -verify-dom-info < %s |
>> FileCheck %s
>>
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> ; STATS: 2 loop-unswitch - Number of switches unswitched
>>
>> ; CHECK: %1 = icmp eq i32 %c, 1
>>
>> Modified: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-
>> TwoSwitches-Threshold.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
>> Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.
>> ll?rev=306252&r1=306251&r2=306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
>> (original)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
>> Sun Jun 25 10:58:25 2017
>> @@ -2,6 +2,7 @@
>> ; RUN: opt -loop-unswitch -loop-unswitch-threshold 13 -disable-output
>> -stats -info-output-file - < %s | FileCheck --check-prefix=STATS %s
>> ; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 13
>> -verify-loop-info -verify-dom-info < %s | FileCheck %s
>>
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> ; STATS: 1 loop-unswitch - Number of switches unswitched
>>
>> ; ModuleID = '../llvm/test/Transforms/LoopUnswitch/2011-11-18-
>> TwoSwitches.ll'
>>
>> Modified: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-
>> TwoSwitches.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
>> Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll?rev=
>> 306252&r1=306251&r2=306252&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
>> (original)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
>> Sun Jun 25 10:58:25 2017
>> @@ -2,6 +2,7 @@
>> ; RUN: opt -loop-unswitch -loop-unswitch-threshold 1000 -disable-output
>> -stats -info-output-file - < %s | FileCheck --check-prefix=STATS %s
>> ; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 1000
>> -verify-loop-info -verify-dom-info < %s | FileCheck %s
>>
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> ; STATS: 3 loop-unswitch - Number of switches unswitched
>>
>> ; CHECK: %1 = icmp eq i32 %c, 1
>>
>>
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>
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