[llvm] r369191 - [CodeGen] Do the Simple Early Return in block-placement pass to optimize the blocks
Fedor Sergeev via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 27 15:35:20 PDT 2019
Please, find reproducer in the comment to the original review:
https://reviews.llvm.org/D63972#1647948
regards,
Fedor.
On 8/27/19 6:08 PM, Jinsong Ji wrote:
>
> @skatkov is also reporting crash in D63972#1646303
> Contacted @ZhangKang, and revert the commit on behalf of him in
> https://reviews.llvm.org/rL370069.
>
> Reproducer is appreciated. Thanks.
>
>
> Best,
>
> Jinsong Ji (纪金松), PhD.
>
> XL/LLVM on Power Compiler Development
> E-mail: jji at us.ibm.com
>
> Inactive hide details for "Mikael Holmén via llvm-commits"
> ---08/27/2019 01:20:47 AM---On Tue, 2019-08-27 at 01:01 +0300,
> Fedor"Mikael Holmén via llvm-commits" ---08/27/2019 01:20:47 AM---On
> Tue, 2019-08-27 at 01:01 +0300, Fedor Sergeev wrote: > Hmm... we are
> seeing problems with X86 bac
>
> From: "Mikael Holmén via llvm-commits" <llvm-commits at lists.llvm.org>
> To: "fedor.sergeev at azul.com" <fedor.sergeev at azul.com>,
> "shkzhang at cn.ibm.com" <shkzhang at cn.ibm.com>
> Cc: "llvm-commits at lists.llvm.org" <llvm-commits at lists.llvm.org>
> Date: 08/27/2019 01:20 AM
> Subject: [EXTERNAL] Re: [llvm] r369191 - [CodeGen] Do the Simple Early
> Return in block-placement pass to optimize the blocks
> Sent by: "llvm-commits" <llvm-commits-bounces at lists.llvm.org>
>
> ------------------------------------------------------------------------
>
>
>
> On Tue, 2019-08-27 at 01:01 +0300, Fedor Sergeev wrote:
> > Hmm... we are seeing problems with X86 backend (and our Java JIT
> > frontend) that we managed
> > to bisect down to this change.
> > I might be able to provide a clean reproducer tomorrow.
> >
> > Meanwhile, Mikael, was there a bug filed?
> > I dont see any followup commits related to this....
> >
>
> Hi,
>
> Turned out my problem was specific to my out-of-tree backend where we
> run MBP both before and after regalloc.
>
> When we ran it before RA (which isn't done in-tree anywhere as far as I
> know) it didn't update PHIs when it changed the CFG and then the
> verifier complained.
>
> /Mikael
>
> > regards,
> > Fedor.
> >
> >
> > On 8/23/19 4:36 PM, Mikael Holmén via llvm-commits wrote:
> > > Hi,
> > >
> > > We're seeing a problem with this commit for our out-of-tree
> > > backend.
> > >
> > > Before 'Early Branch Probability Basic Block Placement':
> > >
> > > bb.2.cond.end.thread:
> > > ; predecessors: %bb.1
> > > successors: %bb.5(0x80000000); %bb.5(100.00%)
> > >
> > > brr_uncond %bb.5
> > >
> > > [...]
> > >
> > > bb.5.land.lhs.true28:
> > > ; predecessors: %bb.2, %bb.3
> > > successors: %bb.6(0x30000000), %bb.7(0x50000000);
> > > %bb.6(37.50%),
> > > %bb.7(62.50%)
> > >
> > > %8:an32_rn_pairs = ...
> > > cmp ...
> > > brr_cond %bb.7
> > > brr_uncond %bb.6
> > >
> > > [...]
> > >
> > > bb.7.cond.end38:
> > > ; predecessors: %bb.5, %bb.4, %bb.6
> > > successors: %bb.8(0x00000001), %bb.9(0x7fffffff); %bb.8(0.00%),
> > > %bb.9(100.00%)
> > >
> > > %2:an32_0_7 = PHI %8:an32_rn_pairs, %bb.5, %11:an32_rn_pairs,
> > > %bb.4,
> > > %0:an32_rn_pairs, %bb.6
> > > cmps ...
> > > brr_cond %bb.9
> > > brr_uncond %bb.8
> > >
> > >
> > > and after:
> > >
> > > bb.2.cond.end.thread:
> > > ; predecessors: %bb.1, %bb.3
> > > successors: %bb.7(0x50000000), %bb.6(0x30000000);
> > > %bb.7(62.50%),
> > > %bb.6(37.50%)
> > >
> > > %8:an32_rn_pairs =...
> > > cmp ...
> > > brr_cond %bb.7
> > > brr_uncond %bb.6
> > >
> > > [...]
> > >
> > > bb.7.cond.end38:
> > > ; predecessors: %bb.4, %bb.6, %bb.2
> > > successors: %bb.8(0x00000001), %bb.9(0x7fffffff); %bb.8(0.00%),
> > > %bb.9(100.00%)
> > >
> > > %2:an32_0_7 = PHI %8:an32_rn_pairs, %bb.-1, %11:an32_rn_pairs,
> > > %bb.4,
> > > %0:an32_rn_pairs, %bb.6
> > > cmps ...
> > > brr_cond %bb.8
> > >
> > >
> > > So it looks like it's failed to update the PHI operand for %bb.5 in
> > > %2
> > > properly leaving it now with %bb.-1?
> > >
> > > Any idea?
> > >
> > > /Mikael
> > >
> > > On 2019-08-17 16:37, Kang Zhang via llvm-commits wrote:
> > > > Author: zhangkang
> > > > Date: Sat Aug 17 07:37:05 2019
> > > > New Revision: 369191
> > > >
> > > > URL:
> > > >
> https://protect2.fireeye.com/url?k=6f40a04c-3393b024-6f40e0d7-8691b328a8b8-90715b879d6c2a6b&q=1&u=http%3A%2F%2Fllvm.org%2Fviewvc%2Fllvm-project%3Frev%3D369191%26view%3Drev
> > > > Log:
> > > > [CodeGen] Do the Simple Early Return in block-placement pass to
> > > > optimize the blocks
> > > >
> > > > Summary:
> > > >
> > > > Fix a bug of preducessors.
> > > >
> > > > In `block-placement` pass, it will create some patterns for
> > > > unconditional we can do the simple early retrun.
> > > > But the `early-ret` pass is before `block-placement`, we don't
> > > > want to run it again.
> > > > This patch is to do the simple early return to optimize the
> > > > blocks at the last of `block-placement`.
> > > >
> > > > Reviewed By: efriedma
> > > >
> > > > Differential Revision:
> > > >
> https://protect2.fireeye.com/url?k=af91b373-f342a31b-af91f3e8-8691b328a8b8-a356f6b65b5e7513&q=1&u=https%3A%2F%2Freviews.llvm.org%2FD63972
> > > >
> > > > Modified:
> > > > llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
> > > > llvm/trunk/test/CodeGen/PowerPC/block-placement.mir
> > > >
> > > > Modified: llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
> > > > URL:
> > > >
> https://protect2.fireeye.com/url?k=44a01ed0-18730eb8-44a05e4b-8691b328a8b8-590610f76548b1fa&q=1&u=http%3A%2F%2Fllvm.org%2Fviewvc%2Fllvm-project%2Fllvm%2Ftrunk%2Flib%2FCodeGen%2FMachineBlockPlacement.cpp%3Frev%3D369191%26r1%3D369190%26r2%3D369191%26view%3Ddiff
> > > > =================================================================
> > > > =============
> > > > --- llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp (original)
> > > > +++ llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp Sat Aug 17
> > > > 07:37:05 2019
> > > > @@ -2711,6 +2711,7 @@ void MachineBlockPlacement::optimizeBran
> > > > // cannot because all branches may not be analyzable.
> > > > // E.g., the target may be able to remove an unconditional
> > > > branch to
> > > > // a fallthrough when it occurs after predicated
> > > > terminators.
> > > > + SmallVector<MachineBasicBlock*, 4> EmptyBB;
> > > > for (MachineBasicBlock *ChainBB : FunctionChain) {
> > > > Cond.clear();
> > > > MachineBasicBlock *TBB = nullptr, *FBB = nullptr; // For
> > > > AnalyzeBranch.
> > > > @@ -2730,9 +2731,45 @@ void MachineBlockPlacement::optimizeBran
> > > > TII->removeBranch(*ChainBB);
> > > > TII->insertBranch(*ChainBB, FBB, TBB, Cond, dl);
> > > > ChainBB->updateTerminator();
> > > > + } else if (Cond.empty() && TBB && ChainBB != TBB && !TBB-
> > > > >empty() &&
> > > > + !TBB->canFallThrough()) {
> > > > + // When ChainBB is unconditional branch to the TBB, and
> > > > TBB has no
> > > > + // fallthrough predecessor and fallthrough successor,
> > > > try to merge
> > > > + // ChainBB and TBB. This is legal under the one of
> > > > following conditions:
> > > > + // 1. ChainBB is empty except for an unconditional
> > > > branch.
> > > > + // 2. TBB has only one predecessor.
> > > > + MachineFunction::iterator I(TBB);
> > > > + if (((TBB == &*F->begin()) || !std::prev(I)-
> > > > >canFallThrough()) &&
> > > > + (TailDup.isSimpleBB(ChainBB) || (TBB->pred_size()
> > > > == 1))) {
> > > > + TII->removeBranch(*ChainBB);
> > > > + ChainBB->removeSuccessor(TBB);
> > > > +
> > > > + // Update the CFG.
> > > > + while (!TBB->pred_empty()) {
> > > > + MachineBasicBlock *Pred = *(TBB->pred_end() - 1);
> > > > + Pred->ReplaceUsesOfBlockWith(TBB, ChainBB);
> > > > + }
> > > > +
> > > > + while (!TBB->succ_empty()) {
> > > > + MachineBasicBlock *Succ = *(TBB->succ_end() - 1);
> > > > + ChainBB->addSuccessor(Succ, MBPI-
> > > > >getEdgeProbability(TBB, Succ));
> > > > + TBB->removeSuccessor(Succ);
> > > > + }
> > > > +
> > > > + // Move all the instructions of TBB to ChainBB.
> > > > + ChainBB->splice(ChainBB->end(), TBB, TBB->begin(),
> > > > TBB->end());
> > > > + EmptyBB.push_back(TBB);
> > > > + }
> > > > }
> > > > }
> > > > }
> > > > +
> > > > + for (auto BB: EmptyBB) {
> > > > + MLI->removeBlock(BB);
> > > > + FunctionChain.remove(BB);
> > > > + BlockToChain.erase(BB);
> > > > + F->erase(BB);
> > > > + }
> > > > }
> > > >
> > > > void MachineBlockPlacement::alignBlocks() {
> > > > @@ -3052,6 +3089,9 @@ bool MachineBlockPlacement::runOnMachine
> > > > }
> > > > }
> > > >
> > > > + // optimizeBranches() may change the blocks, but we haven't
> > > > updated the
> > > > + // post-dominator tree. Because the post-dominator tree won't
> > > > be used after
> > > > + // this function and this pass don't preserve the post-
> > > > dominator tree.
> > > > optimizeBranches();
> > > > alignBlocks();
> > > >
> > > >
> > > > Modified: llvm/trunk/test/CodeGen/PowerPC/block-placement.mir
> > > > URL:
> > > >
> https://protect2.fireeye.com/url?k=c2447a57-9e976a3f-c2443acc-8691b328a8b8-7cd3fcb165ec6683&q=1&u=http%3A%2F%2Fllvm.org%2Fviewvc%2Fllvm-project%2Fllvm%2Ftrunk%2Ftest%2FCodeGen%2FPowerPC%2Fblock-placement.mir%3Frev%3D369191%26r1%3D369190%26r2%3D369191%26view%3Ddiff
> > > > =================================================================
> > > > =============
> > > > --- llvm/trunk/test/CodeGen/PowerPC/block-placement.mir
> > > > (original)
> > > > +++ llvm/trunk/test/CodeGen/PowerPC/block-placement.mir Sat Aug
> > > > 17 07:37:05 2019
> > > > @@ -209,14 +209,10 @@ body: |
> > > > BLR8 implicit $lr8, implicit $rm, implicit killed $x3
> > > >
> > > > ; CHECK: bb.5.if.else.i:
> > > > - ; CHECK: successors: %bb.11(0x80000000)
> > > > - ; CHECK: B %bb.11
> > > > + ; CHECK-NEXT: renamable $x3 = LI8 1
> > > > + ; CHECK-NEXT: BLR8 implicit $lr8, implicit $rm, implicit
> > > > killed $x3
> > > >
> > > > ; CHECK: bb.8.while.body.i (align 4):
> > > > - ; CHECK: successors: %bb.11(0x04000000),
> > > > %bb.9(0x7c000000)
> > > > - ; CHECK: BCC 76, killed renamable $cr0, %bb.11
> > > > -
> > > > - ; CHECK: bb.11:
> > > > - ; CHECK: renamable $x3 = LI8 1
> > > > - ; CHECK-NEXT: BLR8 implicit $lr8, implicit $rm, implicit
> > > > killed $x3
> > > > + ; CHECK: successors: %bb.5(0x04000000),
> > > > %bb.9(0x7c000000)
> > > > + ; CHECK: BCC 76, killed renamable $cr0, %bb.5
> > > > ...
> > > >
> > > >
> > > > _______________________________________________
> > > > llvm-commits mailing list
> > > > llvm-commits at lists.llvm.org
> > > >
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