[llvm] r264596 - [SimlifyCFG] Prevent passes from destroying canonical loop structure, especially for nested loops
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 10 09:40:17 PDT 2016
Great, thanks for catching that.
On Tue, Aug 9, 2016 at 11:13 PM, Michael Kuperstein <
michael.kuperstein at gmail.com> wrote:
> Looks like a dup of PR28541, there's already patch that fixes it under
> review (D22952).
>
> Michael
>
> On 9 August 2016 at 19:42, Hans Wennborg via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> This commit seems to have caused https://llvm.org/bugs/s
>> how_bug.cgi?id=28190
>>
>> Hyojin, can you please investigate?
>>
>> I also wonder if anyone reviewed this patch, and if some motivating test
>> case should have been added.
>>
>> Thanks,
>> Hans
>>
>> On Mon, Mar 28, 2016 at 9:41 PM, Hyojin Sung via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> My apologies. I fixed the patch, checked it compiles, and submitted a
>>> new commit.
>>>
>>> Regards,
>>> Hyojin
>>>
>>> [image: Inactive hide details for Reid Kleckner ---03/28/2016 02:19:24
>>> PM---I reverted this because it didn't compile. You referenced a]Reid
>>> Kleckner ---03/28/2016 02:19:24 PM---I reverted this because it didn't
>>> compile. You referenced a field of SimplifyCFGOpt from a static he
>>>
>>> From: Reid Kleckner <rnk at google.com>
>>> To: Hyojin Sung/Watson/IBM at IBMUS
>>> Cc: llvm-commits <llvm-commits at lists.llvm.org>
>>> Date: 03/28/2016 02:19 PM
>>> Subject: Re: [llvm] r264596 - [SimlifyCFG] Prevent passes from
>>> destroying canonical loop structure, especially for nested loops
>>> ------------------------------
>>>
>>>
>>>
>>> I reverted this because it didn't compile. You referenced a field of
>>> SimplifyCFGOpt from a static helper function.
>>>
>>> On Mon, Mar 28, 2016 at 10:22 AM, Hyojin Sung via llvm-commits <
>>> *llvm-commits at lists.llvm.org* <llvm-commits at lists.llvm.org>> wrote:
>>>
>>> Author: hsung
>>> Date: Mon Mar 28 12:22:25 2016
>>> New Revision: 264596
>>>
>>> URL: *http://llvm.org/viewvc/llvm-project?rev=264596&view=rev*
>>> <http://llvm.org/viewvc/llvm-project?rev=264596&view=rev>
>>> Log:
>>> [SimlifyCFG] Prevent passes from destroying canonical loop
>>> structure, especially for nested loops
>>>
>>> When eliminating or merging almost empty basic blocks, the existence
>>> of non-trivial PHI nodes
>>> is currently used to recognize potential loops of which the block is
>>> the header and keep the block.
>>> However, the current algorithm fails if the loops' exit condition is
>>> evaluated only with volatile
>>> values hence no PHI nodes in the header. Especially when such a loop
>>> is an outer loop of a nested
>>> loop, the loop is collapsed into a single loop which prevent later
>>> optimizations from being
>>> applied (e.g., transforming nested loops into simplified forms and
>>> loop vectorization).
>>>
>>> The patch augments the existing PHI node-based check by adding a
>>> pre-test if the BB actually
>>> belongs to a set of loop headers and not eliminating it if yes.
>>>
>>>
>>> Modified:
>>> llvm/trunk/include/llvm/Transforms/Utils/Local.h
>>> llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
>>> llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
>>> llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>>> llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll
>>> llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll
>>> llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMe
>>> rge.ll
>>> llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
>>>
>>> Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
>>> +++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Mon Mar 28
>>> 12:22:25 2016
>>> @@ -21,6 +21,7 @@
>>> #include "llvm/IR/GetElementPtrTypeIterator.h"
>>> #include "llvm/IR/IRBuilder.h"
>>> #include "llvm/IR/Operator.h"
>>> +#include "llvm/ADT/SmallPtrSet.h"
>>>
>>> namespace llvm {
>>>
>>> @@ -124,13 +125,16 @@ bool TryToSimplifyUncondBranchFromEmptyB
>>> /// values, but instcombine orders them so it usually won't matter.
>>> bool EliminateDuplicatePHINodes(BasicBlock *BB);
>>>
>>> -/// This function is used to do simplification of a CFG. For
>>> example, it
>>> -/// adjusts branches to branches to eliminate the extra hop, it
>>> eliminates
>>> -/// unreachable basic blocks, and does other "peephole"
>>> optimization of the CFG.
>>> -/// It returns true if a modification was made, possibly deleting
>>> the basic
>>> -/// block that was pointed to.
>>> +/// This function is used to do simplification of a CFG. For
>>> +/// example, it adjusts branches to branches to eliminate the extra
>>> hop, it
>>> +/// eliminates unreachable basic blocks, and does other "peephole"
>>> optimization
>>> +/// of the CFG. It returns true if a modification was made,
>>> possibly deleting
>>> +/// the basic block that was pointed to. LoopHeaders is an optional
>>> input
>>> +/// parameter, providing the set of loop header that SimplifyCFG
>>> should not
>>> +/// eliminate.
>>> bool SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
>>> - unsigned BonusInstThreshold, AssumptionCache *AC =
>>> nullptr);
>>> + unsigned BonusInstThreshold, AssumptionCache *AC =
>>> nullptr,
>>> + SmallPtrSetImpl<BasicBlock *> *LoopHeaders =
>>> nullptr);
>>>
>>> /// This function is used to flatten a CFG. For example, it uses
>>> parallel-and
>>> /// and parallel-or mode to collapse if-conditions and merge
>>> if-regions with
>>>
>>> Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Mon Mar 28
>>> 12:22:25 2016
>>> @@ -245,10 +245,13 @@ bool JumpThreading::runOnFunction(Functi
>>> // Can't thread an unconditional jump, but if the block is
>>> "almost
>>> // empty", we can replace uses of it with uses of the
>>> successor and make
>>> // this dead.
>>> + // We should not eliminate the loop header either, because
>>> eliminating
>>> + // a loop header might later prevent LoopSimplify from
>>> transforming nested
>>> + // loops into simplified form.
>>> if (BI && BI->isUnconditional() &&
>>> BB != &BB->getParent()->getEntryBlock() &&
>>> // If the terminator is the only non-phi instruction, try
>>> to nuke it.
>>> - BB->getFirstNonPHIOrDbg()->isTerminator()) {
>>> + BB->getFirstNonPHIOrDbg()->isTerminator() &&
>>> !LoopHeaders.count(BB)) {
>>> // Since TryToSimplifyUncondBranchFromEmptyBlock may delete
>>> the
>>> // block, we have to make sure it isn't in the LoopHeaders
>>> set. We
>>> // reinsert afterward if needed.
>>>
>>> Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp Mon Mar 28
>>> 12:22:25 2016
>>> @@ -28,6 +28,7 @@
>>> #include "llvm/Analysis/GlobalsModRef.h"
>>> #include "llvm/Analysis/AssumptionCache.h"
>>> #include "llvm/Analysis/TargetTransformInfo.h"
>>> +#include "llvm/Analysis/CFG.h"
>>> #include "llvm/IR/Attributes.h"
>>> #include "llvm/IR/CFG.h"
>>> #include "llvm/IR/Constants.h"
>>> @@ -130,13 +131,20 @@ static bool iterativelySimplifyCFG(Funct
>>> AssumptionCache *AC,
>>> unsigned BonusInstThreshold) {
>>> bool Changed = false;
>>> - bool LocalChange = true;
>>> + bool LocalChange = true;
>>> +
>>> + SmallVector<std::pair<const BasicBlock *, const BasicBlock *>,
>>> 32> Edges;
>>> + FindFunctionBackedges(F, Edges);
>>> + SmallPtrSet<BasicBlock *, 16> LoopHeaders;
>>> + for (unsigned i = 0, e = Edges.size(); i != e; ++i)
>>> + LoopHeaders.insert(const_cast<BasicBlock *>(Edges[i].second));
>>> +
>>> while (LocalChange) {
>>> LocalChange = false;
>>>
>>> // Loop over all of the basic blocks and remove them if they
>>> are unneeded.
>>> for (Function::iterator BBIt = F.begin(); BBIt != F.end(); ) {
>>> - if (SimplifyCFG(&*BBIt++, TTI, BonusInstThreshold, AC)) {
>>> + if (SimplifyCFG(&*BBIt++, TTI, BonusInstThreshold, AC,
>>> &LoopHeaders)) {
>>> LocalChange = true;
>>> ++NumSimpl;
>>> }
>>>
>>> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Mar 28
>>> 12:22:25 2016
>>> @@ -135,6 +135,7 @@ class SimplifyCFGOpt {
>>> const DataLayout &DL;
>>> unsigned BonusInstThreshold;
>>> AssumptionCache *AC;
>>> + SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
>>> Value *isValueEqualityComparison(TerminatorInst *TI);
>>> BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
>>> std::vector<ValueEqualityComparisonCase>
>>> &Cases);
>>> @@ -157,8 +158,10 @@ class SimplifyCFGOpt {
>>>
>>> public:
>>> SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout
>>> &DL,
>>> - unsigned BonusInstThreshold, AssumptionCache *AC)
>>> - : TTI(TTI), DL(DL), BonusInstThreshold(BonusInstThreshold),
>>> AC(AC) {}
>>> + unsigned BonusInstThreshold, AssumptionCache *AC,
>>> + SmallPtrSetImpl<BasicBlock *> *LoopHeaders)
>>> + : TTI(TTI), DL(DL), BonusInstThreshold(BonusInstThreshold),
>>> AC(AC),
>>> + LoopHeaders(LoopHeaders) {}
>>> bool run(BasicBlock *BB);
>>> };
>>> }
>>> @@ -3362,6 +3365,7 @@ bool SimplifyCFGOpt::SimplifySingleResum
>>>
>>> // The landingpad is now unreachable. Zap it.
>>> BB->eraseFromParent();
>>> + if (LoopHeaders) LoopHeaders->erase(BB);
>>> return true;
>>> }
>>>
>>> @@ -3480,6 +3484,7 @@ static bool removeEmptyCleanup(CleanupRe
>>>
>>> // The cleanup pad is now unreachable. Zap it.
>>> BB->eraseFromParent();
>>> + if (LoopHeaders) LoopHeaders->erase(BB);
>>> return true;
>>> }
>>>
>>> @@ -3560,9 +3565,11 @@ bool SimplifyCFGOpt::SimplifyReturn(Retu
>>> }
>>>
>>> // If we eliminated all predecessors of the block, delete the
>>> block now.
>>> - if (pred_empty(BB))
>>> + if (pred_empty(BB)) {
>>> // We know there are no successors, so just nuke the block.
>>> BB->eraseFromParent();
>>> + if (LoopHeaders) LoopHeaders->erase(BB);
>>> + }
>>>
>>> return true;
>>> }
>>> @@ -3719,6 +3726,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable
>>> BB != &BB->getParent()->getEntryBlock()) {
>>> // We know there are no successors, so just nuke the block.
>>> BB->eraseFromParent();
>>> + if (LoopHeaders) LoopHeaders->erase(BB);
>>> return true;
>>> }
>>>
>>> @@ -5062,8 +5070,14 @@ bool SimplifyCFGOpt::SimplifyUncondBranc
>>> return true;
>>>
>>> // If the Terminator is the only non-phi instruction, simplify
>>> the block.
>>> + // if LoopHeader is provided, check if the block is a loop header
>>> + // (This is for early invocations before loop simplify and
>>> vectorization
>>> + // to keep canonical loop forms for nested loops.
>>> + // These blocks can be eliminated when the pass is invoked later
>>> + // in the back-end.)
>>> BasicBlock::iterator I = BB->getFirstNonPHIOrDbg()->getIterator();
>>> if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock()
>>> &&
>>> + (!LoopHeaders || (LoopHeaders && !LoopHeaders->count(BB))) &&
>>> TryToSimplifyUncondBranchFromEmptyBlock(BB))
>>> return true;
>>>
>>> @@ -5343,7 +5357,8 @@ bool SimplifyCFGOpt::run(BasicBlock *BB)
>>> /// of the CFG. It returns true if a modification was made.
>>> ///
>>> bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo
>>> &TTI,
>>> - unsigned BonusInstThreshold, AssumptionCache
>>> *AC) {
>>> + unsigned BonusInstThreshold, AssumptionCache
>>> *AC,
>>> + SmallPtrSetImpl<BasicBlock *> *LoopHeaders) {
>>> return SimplifyCFGOpt(TTI, BB->getModule()->getDataLayout(),
>>> - BonusInstThreshold, AC).run(BB);
>>> + BonusInstThreshold, AC,
>>> LoopHeaders).run(BB);
>>> }
>>>
>>> Modified: llvm/trunk/test/Transforms/Loo
>>> pUnswitch/2015-06-17-Metadata.ll
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll
>>> (original)
>>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll
>>> Mon Mar 28 12:22:25 2016
>>> @@ -16,23 +16,23 @@ for.body:
>>> %cmp1 = icmp eq i32 %a, 12345
>>> br i1 %cmp1, label %if.then, label %if.else, !prof !0
>>> ; CHECK: %cmp1 = icmp eq i32 %a, 12345
>>> -; CHECK-NEXT: br i1 %cmp1, label %*if.then.us* <http://if.then.us/>,
>>> label %if.else, !prof !0
>>> +; CHECK-NEXT: br i1 %cmp1, label %*for.body.us*
>>> <http://for.body.us/>, label %for.body, !prof !0
>>> if.then: ; preds =
>>> %for.body
>>> -; CHECK: *if.then.us* <http://if.then.us/>:
>>> +; CHECK: *for.body.us* <http://for.body.us/>:
>>> ; CHECK: add nsw i32 %{{.*}}, 123
>>> ; CHECK: %*exitcond.us* <http://exitcond.us/> = icmp eq i32 %
>>> *inc.us* <http://inc.us/>, %b
>>> -; CHECK: br i1 %*exitcond.us* <http://exitcond.us/>, label
>>> %for.cond.cleanup, label %*if.then.us* <http://if.then.us/>
>>> +; CHECK: br i1 %*exitcond.us* <http://exitcond.us/>, label
>>> %for.cond.cleanup, label %*for.body.us* <http://for.body.us/>
>>> %add = add nsw i32 %add.i, 123
>>> br label %for.inc
>>>
>>> if.else: ; preds =
>>> %for.body
>>> %mul = mul nsw i32 %mul.i, %b
>>> br label %for.inc
>>> -; CHECK: if.else:
>>> +; CHECK: for.body:
>>> ; CHECK: %mul = mul nsw i32 %mul.i, %b
>>> ; CHECK: %inc = add nuw nsw i32 %inc.i, 1
>>> ; CHECK: %exitcond = icmp eq i32 %inc, %b
>>> -; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %if.else
>>> +; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %for.body
>>> for.inc: ; preds =
>>> %if.then, %if.else
>>> %mul.p = phi i32 [ %b, %if.then ], [ %mul, %if.else ]
>>> %add.p = phi i32 [ %add, %if.then ], [ %a, %if.else ]
>>>
>>> Modified: llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll
>>> (original)
>>> +++ llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll Mon Mar
>>> 28 12:22:25 2016
>>> @@ -16,10 +16,10 @@
>>> ; CHECK-NEXT: br i1 %a, label %entry.split, label %abort0.split
>>>
>>> ; CHECK: entry.split:
>>> -; CHECK-NEXT: br i1 %b, label %cond.end, label %abort1.split
>>> +; CHECK-NEXT: br i1 %b, label %for.body, label %abort1.split
>>>
>>> -; CHECK: cond.end:
>>> -; CHECK-NEXT: br label %cond.end
>>> +; CHECK: for.body:
>>> +; CHECK-NEXT: br label %for.body
>>>
>>> ; CHECK: abort0.split:
>>> ; CHECK-NEXT: call void @end0() [[NOR_NUW:#[0-9]+]]
>>>
>>> Modified: llvm/trunk/test/Transforms/Sim
>>> plifyCFG/2008-05-16-PHIBlockMerge.ll
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
>>> (original)
>>> +++ llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
>>> Mon Mar 28 12:22:25 2016
>>> @@ -1,6 +1,6 @@
>>> ; RUN: opt < %s -simplifycfg -S > %t
>>> ; RUN: not grep "^BB.tomerge" %t
>>> -; RUN: grep "^BB.nomerge" %t | count 2
>>> +; RUN: grep "^BB.nomerge" %t | count 4
>>>
>>> ; ModuleID = '<stdin>'
>>> declare i1 @foo()
>>> @@ -54,24 +54,24 @@ Exit: ; preds = %Succ
>>> ret void
>>> }
>>>
>>> -; This function can be merged
>>> +; This function can't be merged (for keeping canonical loop
>>> structures)
>>> define void @c() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %BB.nomerge
>>>
>>> -BB.tomerge: ; preds = %Common, %entry
>>> +BB.nomerge: ; preds = %Common, %entry
>>> br label %Succ
>>>
>>> Succ: ; preds = %Common, %BB.tomerge, %Pre-Exit
>>> ; This phi has identical values for Common and (through BB)
>>> Common,
>>> ; blocks can't be merged
>>> - %b = phi i32 [ 1, %BB.tomerge ], [ 1, %Common ], [ 2,
>>> %Pre-Exit ]
>>> + %b = phi i32 [ 1, %BB.nomerge ], [ 1, %Common ], [ 2,
>>> %Pre-Exit ]
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Common, label %Pre-Exit
>>>
>>> Common: ; preds = %Succ
>>> %cond = call i1 @foo( ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Succ
>>> + br i1 %cond, label %BB.nomerge, label %Succ
>>>
>>> Pre-Exit: ; preds = %Succ
>>> ; This adds a backedge, so the %b phi node gets a third
>>> branch and is
>>> @@ -83,25 +83,25 @@ Exit: ; preds = %Pre-Exit
>>> ret void
>>> }
>>>
>>> -; This function can be merged
>>> +; This function can't be merged (for keeping canonical loop
>>> structures)
>>> define void @d() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %BB.nomerge
>>>
>>> -BB.tomerge: ; preds = %Common, %entry
>>> +BB.nomerge: ; preds = %Common, %entry
>>> ; This phi has a matching value (0) with below phi (0), so
>>> blocks
>>> ; can be merged.
>>> %a = phi i32 [ 1, %entry ], [ 0, %Common ] ;
>>> <i32> [#uses=1]
>>> br label %Succ
>>>
>>> Succ: ; preds = %Common, %BB.tomerge
>>> - %b = phi i32 [ %a, %BB.tomerge ], [ 0, %Common ]
>>> ; <i32> [#uses=0]
>>> + %b = phi i32 [ %a, %BB.nomerge ], [ 0, %Common ]
>>> ; <i32> [#uses=0]
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Common, label %Exit
>>>
>>> Common: ; preds = %Succ
>>> %cond = call i1 @foo( ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Succ
>>> + br i1 %cond, label %BB.nomerge, label %Succ
>>>
>>> Exit: ; preds = %Succ
>>> ret void
>>> @@ -110,21 +110,21 @@ Exit: ; preds = %Succ
>>> ; This function can be merged
>>> define void @e() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %Succ
>>>
>>> -BB.tomerge: ; preds = %Use, %entry
>>> +Succ: ; preds = %Use, %entry
>>> ; This phi is used somewhere else than Succ, but this
>>> should not prevent
>>> ; merging this block
>>> %a = phi i32 [ 1, %entry ], [ 0, %Use ] ; <i32>
>>> [#uses=1]
>>> - br label %Succ
>>> + br label %BB.tomerge
>>>
>>> -Succ: ; preds = %BB.tomerge
>>> +BB.tomerge: ; preds = %BB.tomerge
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Use, label %Exit
>>>
>>> Use: ; preds = %Succ
>>> %cond = call i1 @bar( i32 %a ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Exit
>>> + br i1 %cond, label %Succ, label %Exit
>>>
>>> Exit: ; preds = %Use, %Succ
>>> ret void
>>>
>>> Modified: llvm/trunk/test/Transforms/Sim
>>> plifyCFG/EqualPHIEdgeBlockMerge.ll
>>> URL:
>>> *http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll?rev=264596&r1=264595&r2=264596&view=diff*
>>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll?rev=264596&r1=264595&r2=264596&view=diff>
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
>>> (original)
>>> +++ llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
>>> Mon Mar 28 12:22:25 2016
>>> @@ -5,7 +5,7 @@
>>> ; RUN: not grep X: %t
>>> ; RUN: not grep 'switch i32[^U]+%U' %t
>>> ; RUN: not grep "^BB.tomerge" %t
>>> -; RUN: grep "^BB.nomerge" %t | count 2
>>> +; RUN: grep "^BB.nomerge" %t | count 4
>>> ;
>>>
>>> ; ModuleID = '<stdin>'
>>> @@ -179,24 +179,24 @@ Exit: ; preds = %Succ
>>> ret void
>>> }
>>>
>>> -; This function can be merged
>>> +; This function can't be merged (for keeping canonical loop
>>> structures)
>>> define void @c() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %BB.nomerge
>>>
>>> -BB.tomerge: ; preds = %Common, %entry
>>> +BB.nomerge: ; preds = %Common, %entry
>>> br label %Succ
>>>
>>> Succ: ; preds = %Common, %BB.tomerge, %Pre-Exit
>>> ; This phi has identical values for Common and (through BB)
>>> Common,
>>> ; blocks can't be merged
>>> - %b = phi i32 [ 1, %BB.tomerge ], [ 1, %Common ], [ 2,
>>> %Pre-Exit ]
>>> + %b = phi i32 [ 1, %BB.nomerge ], [ 1, %Common ], [ 2,
>>> %Pre-Exit ]
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Common, label %Pre-Exit
>>>
>>> Common: ; preds = %Succ
>>> %cond = call i1 @foo( ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Succ
>>> + br i1 %cond, label %BB.nomerge, label %Succ
>>>
>>> Pre-Exit: ; preds = %Succ
>>> ; This adds a backedge, so the %b phi node gets a third
>>> branch and is
>>> @@ -208,25 +208,25 @@ Exit: ; preds = %Pre-Exit
>>> ret void
>>> }
>>>
>>> -; This function can be merged
>>> +; This function can't be merged (for keeping canonical loop
>>> structures)
>>> define void @d() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %BB.nomerge
>>>
>>> -BB.tomerge: ; preds = %Common, %entry
>>> +BB.nomerge: ; preds = %Common, %entry
>>> ; This phi has a matching value (0) with below phi (0), so
>>> blocks
>>> ; can be merged.
>>> %a = phi i32 [ 1, %entry ], [ 0, %Common ] ;
>>> <i32> [#uses=1]
>>> br label %Succ
>>>
>>> Succ: ; preds = %Common, %BB.tomerge
>>> - %b = phi i32 [ %a, %BB.tomerge ], [ 0, %Common ]
>>> ; <i32> [#uses=0]
>>> + %b = phi i32 [ %a, %BB.nomerge ], [ 0, %Common ]
>>> ; <i32> [#uses=0]
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Common, label %Exit
>>>
>>> Common: ; preds = %Succ
>>> %cond = call i1 @foo( ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Succ
>>> + br i1 %cond, label %BB.nomerge, label %Succ
>>>
>>> Exit: ; preds = %Succ
>>> ret void
>>> @@ -235,21 +235,21 @@ Exit: ; preds = %Succ
>>> ; This function can be merged
>>> define void @e() {
>>> entry:
>>> - br label %BB.tomerge
>>> + br label %Succ
>>>
>>> -BB.tomerge: ; preds = %Use, %entry
>>> +Succ: ; preds = %Use, %entry
>>> ; This phi is used somewhere else than Succ, but this
>>> should not prevent
>>> ; merging this block
>>> %a = phi i32 [ 1, %entry ], [ 0, %Use ] ; <i32>
>>> [#uses=1]
>>> - br label %Succ
>>> + br label %BB.tomerge
>>>
>>> -Succ: ; preds = %BB.tomerge
>>> +BB.tomerge: ; preds = %Succ
>>> %conde = call i1 @foo( ) ; <i1> [#uses=1]
>>> br i1 %conde, label %Use, label %Exit
>>>
>>> Use: ; preds = %Succ
>>> %cond = call i1 @bar( i32 %a ) ; <i1> [#uses=1]
>>> - br i1 %cond, label %BB.tomerge, label %Exit
>>> + br i1 %cond, label %Succ, label %Exit
>>>
>>> Exit: ; preds = %Use, %Succ
>>> ret void
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> *llvm-commits at lists.llvm.org* <llvm-commits at lists.llvm.org>
>>> *http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits*
>>> <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>>
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