[llvm] r368339 - [MBP] Disable aggressive loop rotate in plain mode

Carrot Wei via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 16 16:09:31 PDT 2019 

Let's go through first 3 instructions of the MBB with more detail:

  DBG_VALUE $edi, $noreg, !"range", !DIExpression(), debug-location
!13632; ../../v8\src/torque/utils.h:0 @[
../../v8/src/torque/csa-generator.cc:94 @[
../../v8/src/torque/csa-generator.cc:76 ] ]
 line no:263
  DBG_VALUE $esi, 0, !"range", !DIExpression(DW_OP_LLVM_fragment, 0,
32), debug-location !13632; ../../v8\src/torque/utils.h:0 @[
../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/cs
a-generator.cc:76 ] ] line no:263 indirect
  renamable $eax = MOV32rm $esi, 1, $noreg, 0, $noreg :: (load 4 from %stack.54)

1 A VarLoc is created, ID is 1844, Var is for "range" without
fragment, Kind is RegisterKind, RegNo is edi

2 A VarLoc is created, ID is 1845, Var is for "range" with fragment,
Kind is RegisterKind, RegNo is esi

3 Function isRestoreInstruction treats this instruction as restore,
and the Loc of restored value is {esi, 0}. Function
transferSpillOrRestoreInst tries to find an existed VarLoc with the
same spilled location

 856     } else if (TKind == TransferKind::TransferRestore &&
 857                VarLocIDs[ID].Loc.SpillLocation == *Loc) {
 858       LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg,
TRI) << '('
 859                         << VarLocIDs[ID].Var.getVar()->getName() << ")\n");

In line 857 VarLocIDs[ID].Loc.SpillLocation is used directly without
first check if VarLocIDs[ID].Kind is SpillLocKind. This should be a
bug.
In this case, when compared with VarLocIDs[1845],
VarLocIDs[1845].Loc.RegNo is esi, the small register number occupies
the lower half, the upper half is 0, when treated as SpillLocation, it
is {esi, 0}, so matches the result of isRestoreInstruction, then
insertTransferDebugPair is called to update OpenRanges, and caused
inconsistent OpenRanges.Vars and OpenRanges.VarLocs.

Debug information experts, is this the root cause?
thanks

On Fri, Aug 16, 2019 at 10:29 AM David Blaikie <dblaikie at gmail.com> wrote:
>
> +other debug info folks
>
> I'm not especially familiar with debug location handling and it's been going through a lot of work lately to improve quality especially with optimized debug info, so perhaps they have some more recent info/experience or can refer you to others that do
>
>
>
> On Thu, Aug 15, 2019, 4:00 PM Carrot Wei <carrot at google.com> wrote:
>>
>> On Thu, Aug 15, 2019 at 8:10 AM Xinliang David Li <xinliangli at gmail.com> wrote:
>> >
>> > So your patch just triggered the bug?  +David Blaikie.
>> >
>> It's very likely a debug information bug just triggered by the MBP
>> patch according to current finding. My understanding of the debug
>> information propagation should not depend on code layout, it depends
>> on data flow and control flow.
>>
>> Before ExtendRanges processing bb62, the MBB looks like
>>
>> bb.62 (%ir-block.187):
>> ; predecessors: %bb.61
>>   successors: %bb.63(0x80000000); %bb.63(100.00%)
>>   liveins: $edi, $edx
>>   renamable $eax = MOV32rm $esi, 1, $noreg, 0, $noreg :: (load 4 from %stack.54)
>>   MOV32mr $esi, 1, $noreg, 24, $noreg, killed renamable $edx :: (store
>> 4 into %stack.56)
>>   renamable $edx = MOV32rm $esi, 1, $noreg, 20, $noreg :: (load 4 from
>> %stack.55)
>>   renamable $eax = SHL32ri killed renamable $eax(tied-def 0), 2,
>> implicit-def dead $eflags, debug-location !13658;
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ..
>> /../v8/src/torque/csa-generator.cc:76 ] ]
>>   renamable $ebx = LEA32r killed renamable $eax, 2, renamable $eax, 0,
>> $noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/to
>> rque/csa-generator.cc:76 ] ]
>>   renamable $eax = LEA32r $noreg, 4, killed renamable $edi, 0, $noreg,
>> debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/csa
>> -generator.cc:76 ] ]
>>   renamable $eax = LEA32r killed renamable $eax, 2, renamable $eax, 0,
>> $noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/to
>> rque/csa-generator.cc:76 ] ]
>>   MOV32mr $esi, 1, $noreg, 0, $noreg, killed renamable $eax :: (store
>> 4 into %stack.54)
>>
>> Then it calls join to propagate the debug information from its
>> predecessors into bb62, bb62 has only 1 predecessor bb61
>>
>> bb.61 (%ir-block.177):
>> ; predecessors: %bb.60
>>   successors: %bb.62(0x40000000), %bb.69(0x40000000); %bb.62(50.00%),
>> %bb.69(50.00%)
>>   liveins: $eax, $ebx, $ecx, $edx
>>   DBG_VALUE $ecx, $noreg, !"range", !DIExpression(DW_OP_LLVM_fragment,
>> 0, 32), debug-location !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torq
>> ue/csa-generator.cc:76 ] ] line no:263
>>   DBG_VALUE $eax, $noreg, !"i", !DIExpression(), debug-location
>> !13633; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] lin
>> e no:266
>>   DBG_VALUE $eax, $noreg, !"range", !DIExpression(DW_OP_LLVM_fragment,
>> 32, 32), debug-location !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/tor
>> que/csa-generator.cc:76 ] ] line no:263
>>   DBG_VALUE $noreg, $noreg, !"this", !DIExpression(), debug-location
>> !13641; ../../v8\src/torque/utils.h:0 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v
>> 8/src/torque/csa-generator.cc:76 ] ] ] line no:0
>>   DBG_VALUE $noreg, $noreg, !"this", !DIExpression(), debug-location
>> !13643; ../../v8\src/torque/utils.h:0 @[
>> ../../v8\src/torque/utils.h:261 @[ ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/to
>> rque/csa-generator.cc:94 @[ ../../v8/src/torque/csa-generator.cc:76 ]
>> ] ] ] line no:0
>>   DBG_VALUE $noreg, $noreg, !"this", !DIExpression(), debug-location
>> !13645; ../../buildtools/third_party/libc++/trunk/include\vector:0 @[
>> ../../v8\src/torque/utils.h:224 @[ ../../v8\src/torque/u
>> tils.h:261 @[ ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ] line no:0
>>   MOV32mr $esi, 1, $noreg, 4, $noreg, killed renamable $eax :: (store
>> 4 into %stack.53)
>>   DBG_VALUE $esi, 0, !"range", !DIExpression(DW_OP_plus_uconst, 4,
>> DW_OP_LLVM_fragment, 32, 32), debug-location !13632;
>> ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>>  ../../v8/src/torque/csa-generator.cc:76 ] ] line no:263 indirect
>>   renamable $eax = MOV32rm renamable $ebx, 1, $noreg, 4, $noreg,
>> debug-location !13647 :: (load 4 from %ir.179);
>> ../../buildtools/third_party/libc++/trunk/include\vector:656 @[
>> ../../v8\src/torqu
>> e/utils.h:224 @[ ../../v8\src/torque/utils.h:261 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ]
>> renamable $edi = MOV32rm renamable $ebx, 1, $noreg, 0, $noreg,
>> debug-location !13647 :: (load 4 from %ir.181);
>> ../../buildtools/third_party/libc++/trunk/include\vector:656 @[
>> ../../v8\src/torqu
>> e/utils.h:224 @[ ../../v8\src/torque/utils.h:261 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ]
>>   MOV32mr $esi, 1, $noreg, 0, $noreg, killed renamable $ecx :: (store
>> 4 into %stack.54)
>>   DBG_VALUE $esi, 0, !"range", !DIExpression(DW_OP_LLVM_fragment, 0,
>> 32), debug-location !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/cs
>> a-generator.cc:76 ] ] line no:263 indirect
>>   $ecx = MOV32rr $eax, debug-location !13647;
>> ../../buildtools/third_party/libc++/trunk/include\vector:656 @[
>> ../../v8\src/torque/utils.h:224 @[ ../../v8\src/torque/utils.h:261 @[
>> ../../v8\src/to
>> rque/utils.h:266 @[ ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ]
>>   MOV32mr $esi, 1, $noreg, 20, $noreg, renamable $edi :: (store 4 into
>> %stack.55)
>>   renamable $ecx = SUB32rr killed renamable $ecx(tied-def 0), killed
>> renamable $edi, implicit-def dead $eflags, debug-location !13647;
>> ../../buildtools/third_party/libc++/trunk/include\vector:656
>>  @[ ../../v8\src/torque/utils.h:224 @[ ../../v8\src/torque/utils.h:261
>> @[ ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ]
>>  ] ] ]
>>   renamable $edi = MOV32rm $esi, 1, $noreg, 4, $noreg :: (load 4 from %stack.53)
>>   DBG_VALUE $edi, $noreg, !"range", !DIExpression(), debug-location
>> !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ]
>>  line no:263
>>   renamable $ecx = exact SAR32ri killed renamable $ecx(tied-def 0), 2,
>> implicit-def dead $eflags, debug-location !13647;
>> ../../buildtools/third_party/libc++/trunk/include\vector:656 @[
>> ../../v8\s
>> rc/torque/utils.h:224 @[ ../../v8\src/torque/utils.h:261 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ]
>>   renamable $ecx = IMUL32rri killed renamable $ecx, -1431655765,
>> implicit-def dead $eflags, debug-location !13647;
>> ../../buildtools/third_party/libc++/trunk/include\vector:656 @[
>> ../../v8\src/tor
>> que/utils.h:224 @[ ../../v8\src/torque/utils.h:261 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ] ] ] ]
>>   DBG_VALUE $noreg, $noreg, !"this", !DIExpression(), debug-location
>> !13655; ../../v8\src/torque/utils.h:0 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v
>> 8/src/torque/csa-generator.cc:76 ] ] ] line no:0
>>   DBG_VALUE $noreg, $noreg, !"other", !DIExpression(), debug-location
>> !13655; ../../v8\src/torque/utils.h:0 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../
>> v8/src/torque/csa-generator.cc:76 ] ] ] line no:169
>>   CMP32rr renamable $ecx, renamable $edi, implicit-def $eflags,
>> debug-location !13657; ../../v8\src/torque/utils.h:170 @[
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:9
>> 4 @[ ../../v8/src/torque/csa-generator.cc:76 ] ] ]
>>   JCC_1 %bb.69, 6, implicit $eflags, debug-location !13658;
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ]
>>
>> This MBB has 5 DBG_VALUE instructions contains information about
>> variable "range". Function join adds 2 DBG_VALUE instructions about
>> variable "range" to bb62
>>
>> bb.62 (%ir-block.187):
>> ; predecessors: %bb.61
>>   successors: %bb.63(0x80000000); %bb.63(100.00%)
>>   liveins: $edi, $edx
>>   DBG_VALUE $edi, $noreg, !"range", !DIExpression(), debug-location
>> !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[
>> ../../v8/src/torque/csa-generator.cc:76 ] ]
>>  line no:263
>>   DBG_VALUE $esi, 0, !"range", !DIExpression(DW_OP_LLVM_fragment, 0,
>> 32), debug-location !13632; ../../v8\src/torque/utils.h:0 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/cs
>> a-generator.cc:76 ] ] line no:263 indirect
>>   renamable $eax = MOV32rm $esi, 1, $noreg, 0, $noreg :: (load 4 from %stack.54)
>>   MOV32mr $esi, 1, $noreg, 24, $noreg, killed renamable $edx :: (store
>> 4 into %stack.56)
>>   renamable $edx = MOV32rm $esi, 1, $noreg, 20, $noreg :: (load 4 from
>> %stack.55)
>>   renamable $eax = SHL32ri killed renamable $eax(tied-def 0), 2,
>> implicit-def dead $eflags, debug-location !13658;
>> ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ..
>> /../v8/src/torque/csa-generator.cc:76 ] ]
>>   renamable $ebx = LEA32r killed renamable $eax, 2, renamable $eax, 0,
>> $noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/to
>> rque/csa-generator.cc:76 ] ]
>>   renamable $eax = LEA32r $noreg, 4, killed renamable $edi, 0, $noreg,
>> debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/csa
>> -generator.cc:76 ] ]
>>   renamable $eax = LEA32r killed renamable $eax, 2, renamable $eax, 0,
>> $noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/to
>> rque/csa-generator.cc:76 ] ]
>>   MOV32mr $esi, 1, $noreg, 0, $noreg, killed renamable $eax :: (store
>> 4 into %stack.54)
>>
>> Then ExtendRanges process instructions in bb62 one by one.
>>
>> 1 the first DBG_VALUE instruction, a DebugVariable about var "range"
>> without fragment information is added to OpenRanges.
>> 2 the second DBG_VALUE instruction, a DebugVariable about var "range"
>> with fragment information is added to OpenRanges.
>> 3 the first MOV32rm instruction, the DebugVariable associated with the
>> second DBG_VALUE instruction is deleted from OpenRanges, a new
>> DebugVariable about var "range" without fragment information is added
>> to OpenRanges, the new DebugVariable is the same as the one associated
>> with the first DBG_VALUE instruction, but with a new ID, the new ID is
>> added to OpenRanges.VarLocs, OpenRanges.Vars is a map, so no new
>> DebugVariable is added to OpenRanges.Vars, it is just updated to map
>> to the new ID. So now OpenRanges.VarLocs and OpenRanges.Vars have
>> different number of elements.
>>
>> Is there anything obviously wrong with these instructions and operations?
>>
>> thanks
>>
>> > David
>> >
>> > On Thu, Aug 15, 2019 at 12:02 AM Carrot Wei via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>> >>
>> >> When function LiveDebugValues::ExtendRanges works on following MBB
>> >>
>> >> bb.62 (%ir-block.187):
>> >> ; predecessors: %bb.61
>> >>   successors: %bb.63(0x80000000); %bb.63(100.00%)
>> >>   liveins: $edi, $edx
>> >>   DBG_VALUE $edi, $noreg, !"range", !DIExpression(), debug-location !136
>> >> 32; ../../v8\src/torque/utils.h:0 @[
>> >> ../../v8/src/torque/csa-generator.cc:94 @[
>> >> ../../v8/src/torque/csa-generator.cc:76 ] ] line no:263
>> >>   DBG_VALUE $esi, 0, !"range", !DIExpression(DW_OP_LLVM_fragment, 0, 32)
>> >> , debug-location !13632; ../../v8\src/torque/utils.h:0 @[ ../../v8/src/t
>> >> orque/csa-generator.cc:94 @[ ../../v8/src/torque/csa-generator.cc:76 ] ]
>> >>  line no:263 indirect
>> >>   renamable $eax = MOV32rm $esi, 1, $noreg, 0, $noreg :: (load 4 from %stack.54)
>> >>   MOV32mr $esi, 1, $noreg, 24, $noreg, killed renamable $edx :: (store 4
>> >>  into %stack.56)
>> >>   renamable $edx = MOV32rm $esi, 1, $noreg, 20, $noreg :: (load 4 from %
>> >> stack.55)
>> >>   renamable $eax = SHL32ri killed renamable $eax(tied-def 0), 2,
>> >> implicit-def dead $eflags, debug-location !13658;
>> >> ../../v8\src/torque/utils.h:2
>> >> 66 @[ ../../v8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/csa
>> >> -generator.cc:76 ] ]
>> >>   renamable $ebx = LEA32r killed renamable $eax, 2, renamable $eax, 0, $
>> >> noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[ ../../v
>> >> 8/src/torque/csa-generator.cc:94 @[ ../../v8/src/torque/csa-generator.cc:76 ] ]
>> >>   renamable $eax = LEA32r $noreg, 4, killed renamable $edi, 0, $noreg, d
>> >> ebug-location !13658; ../../v8\src/torque/utils.h:266 @[ ../../v8/src/to
>> >> rque/csa-generator.cc:94 @[ ../../v8/src/torque/csa-generator.cc:76 ] ]
>> >>   renamable $eax = LEA32r killed renamable $eax, 2, renamable $eax, 0, $
>> >> noreg, debug-location !13658; ../../v8\src/torque/utils.h:266 @[
>> >> ../../v8/src/torque/csa-generator.cc:94 @[
>> >> ../../v8/src/torque/csa-generator.cc
>> >> :76 ] ]
>> >>   MOV32mr $esi, 1, $noreg, 0, $noreg, killed renamable $eax :: (store 4
>> >> into %stack.54)
>> >>
>> >> The data structure OpenRanges got inconsistent internal state. Its
>> >> field OpenRanges.Vars and OpenRanges.VarLocs should have same number
>> >> of elements.
>> >>
>> >> Before handling the third instruction
>> >>
>> >> renamable $eax = MOV32rm $esi, 1, $noreg, 0, $noreg :: (load 4 from %stack.54)
>> >>
>> >> Both OpenRanges.Vars and OpenRanges.VarLocs have 2 elements. Then
>> >> function insertTransferDebugPair is called, it calls OpenRanges.erase
>> >> to delete 1 element from OpenRanges, then both OpenRanges.Vars and
>> >> OpenRanges.VarLocs have 1 element. Later OpenRanges.insert is called
>> >> for the new fragment, this function adds new element to
>> >> OpenRanges.Vars and OpenRanges.VarLocs at the same time, but the
>> >> SmallDenseMap OpenRanges.Vars already has the same key, so
>> >> OpenRanges.Vars just replaced the old value with new one, it still has
>> >> only 1 element, OpenRanges.VarLocs has 2 elements now. Later when
>> >> elements are removed from OpenRanges.Vars, OpenRanges.VarLocs still
>> >> contains 1 value, and caused the assertion failure in function
>> >> OpenRanges.empty.
>> >>
>> >> I'm not familiar with debug information, could anybody help to give me a hint?
>> >>
>> >> thanks a lot!
>> >>
>> >> On Tue, Aug 13, 2019 at 10:45 PM Carrot Wei <carrot at google.com> wrote:
>> >> >
>> >> > I didn't know llvm on linux can cross build windows binary.
>> >> > Now I can reproduce it.
>> >> >
>> >> > On Tue, Aug 13, 2019 at 12:21 AM Hans Wennborg <hans at chromium.org> wrote:
>> >> > >
>> >> > > Did you look at
>> >> > > https://bugs.chromium.org/p/chromium/issues/detail?id=992871#c3 ? It
>> >> > > shows how to reproduce using the tarball on Linux.
>> >> > >
>> >> > > On Mon, Aug 12, 2019 at 8:17 PM Carrot Wei <carrot at google.com> wrote:
>> >> > > >
>> >> > > > The MBP patch doesn't touch debug information, I suspect there is
>> >> > > > something unrelated was triggered.
>> >> > > > I tried your tarball, but found it is for windows, I don't have a
>> >> > > > windows machine :(. Do you have a linux reproduce? It's even better to
>> >> > > > have a compiler command line.
>> >> > > >
>> >> > > > On Mon, Aug 12, 2019 at 7:24 AM Hans Wennborg <hans at chromium.org> wrote:
>> >> > > > >
>> >> > > > > I've reverted this in r368579 since it causes asserts when building
>> >> > > > > Chromium. See https://bugs.chromium.org/p/chromium/issues/detail?id=992871
>> >> > > > > for details and reproducer.
>> >> > > > >
>> >> > > > > On Thu, Aug 8, 2019 at 10:24 PM Guozhi Wei via llvm-commits
>> >> > > > > <llvm-commits at lists.llvm.org> wrote:
>> >> > > > > >
>> >> > > > > > Author: carrot
>> >> > > > > > Date: Thu Aug  8 13:25:23 2019
>> >> > > > > > New Revision: 368339
>> >> > > > > >
>> >> > > > > > URL: http://llvm.org/viewvc/llvm-project?rev=368339&view=rev
>> >> > > > > > Log:
>> >> > > > > > [MBP] Disable aggressive loop rotate in plain mode
>> >> > > > > >
>> >> > > > > > Patch https://reviews.llvm.org/D43256 introduced more aggressive loop layout optimization which depends on profile information. If profile information is not available, the statically estimated profile information(generated by BranchProbabilityInfo.cpp) is used. If user program doesn't behave as BranchProbabilityInfo.cpp expected, the layout may be worse.
>> >> > > > > >
>> >> > > > > > To be conservative this patch restores the original layout algorithm in plain mode. But user can still try the aggressive layout optimization with -force-precise-rotation-cost=true.
>> >> > > > > >
>> >> > > > > > Differential Revision: https://reviews.llvm.org/D65673
>> >> _______________________________________________
>> >> llvm-commits mailing list
>> >> llvm-commits at lists.llvm.org
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