[llvm] r324319 - Revert "[MergeICmps] Enable the MergeICmps Pass by default."

Chandler Carruth via llvm-commits llvm-commits at lists.llvm.org
Tue Feb 6 00:48:56 PST 2018


Ok, last email I promise....

Just realized I was super negative all over this thread, and that isn't
really warranted. Thanks for actually watching the bots and reverting the
patch when something came up! Totally saved me a bunch of time tracking
down the crashes I saw with Clang building itself with PGO enabled that
would have taken probably a lot of time.  Great that we had already gotten
back to green here.

On Tue, Feb 6, 2018 at 12:47 AM Chandler Carruth <chandlerc at gmail.com>
wrote:

> Also, in the future, *please* mention the svn revision you are reverting,
> not just the git commitish. Also useful to follow up on the original commit
> saying it has been reverted. Lots of folks are bisecting failures, and they
> may find the original commit and have no idea that it has been reverted.
>
> On Tue, Feb 6, 2018 at 12:45 AM Chandler Carruth <chandlerc at gmail.com>
> wrote:
>
>> It also appears to break numerous other self-host builds when using PGO
>> of any kind. Just FYI.
>>
>> On Tue, Feb 6, 2018 at 12:41 AM Clement Courbet via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: courbet
>>> Date: Tue Feb  6 00:40:18 2018
>>> New Revision: 324319
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=324319&view=rev
>>> Log:
>>> Revert "[MergeICmps] Enable the MergeICmps Pass by default."
>>>
>>> Breaks clang-ppc64be-linux-multistage buildbot.
>>>
>>> This reverts commit 515bab711f308c2e8299c49dd8c84ea6a2e0b60e.
>>>
>>> Modified:
>>>     llvm/trunk/lib/CodeGen/TargetPassConfig.cpp
>>>     llvm/trunk/test/CodeGen/Generic/llc-start-stop.ll
>>>     llvm/trunk/test/CodeGen/PowerPC/memcmp-mergeexpand.ll
>>>     llvm/trunk/test/CodeGen/X86/memcmp-mergeexpand.ll
>>>
>>> Modified: llvm/trunk/lib/CodeGen/TargetPassConfig.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetPassConfig.cpp?rev=324319&r1=324318&r2=324319&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/CodeGen/TargetPassConfig.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/TargetPassConfig.cpp Tue Feb  6 00:40:18 2018
>>> @@ -94,9 +94,10 @@ static cl::opt<bool> EnableImplicitNullC
>>>      "enable-implicit-null-checks",
>>>      cl::desc("Fold null checks into faulting memory operations"),
>>>      cl::init(false), cl::Hidden);
>>> -static cl::opt<bool> DisableMergeICmps("disable-mergeicmps",
>>> -    cl::desc("Disable MergeICmps Pass"),
>>> -    cl::init(false), cl::Hidden);
>>> +static cl::opt<bool>
>>> +    EnableMergeICmps("enable-mergeicmps",
>>> +                     cl::desc("Merge ICmp chains into a single memcmp"),
>>> +                     cl::init(false), cl::Hidden);
>>>  static cl::opt<bool> PrintLSR("print-lsr-output", cl::Hidden,
>>>      cl::desc("Print LLVM IR produced by the loop-reduce pass"));
>>>  static cl::opt<bool> PrintISelInput("print-isel-input", cl::Hidden,
>>> @@ -595,7 +596,7 @@ void TargetPassConfig::addIRPasses() {
>>>      // loads and compares. ExpandMemCmpPass then tries to expand those
>>> calls
>>>      // into optimally-sized loads and compares. The transforms are
>>> enabled by a
>>>      // target lowering hook.
>>> -    if (!DisableMergeICmps)
>>> +    if (EnableMergeICmps)
>>>        addPass(createMergeICmpsPass());
>>>      addPass(createExpandMemCmpPass());
>>>    }
>>>
>>> Modified: llvm/trunk/test/CodeGen/Generic/llc-start-stop.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Generic/llc-start-stop.ll?rev=324319&r1=324318&r2=324319&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/CodeGen/Generic/llc-start-stop.ll (original)
>>> +++ llvm/trunk/test/CodeGen/Generic/llc-start-stop.ll Tue Feb  6
>>> 00:40:18 2018
>>> @@ -13,15 +13,15 @@
>>>  ; STOP-BEFORE-NOT: Loop Strength Reduction
>>>
>>>  ; RUN: llc < %s -debug-pass=Structure -start-after=loop-reduce -o
>>> /dev/null 2>&1 | FileCheck %s -check-prefix=START-AFTER
>>> -; START-AFTER: -machine-branch-prob -mergeicmps
>>> +; START-AFTER: -machine-branch-prob -expandmemcmp
>>>  ; START-AFTER: FunctionPass Manager
>>> -; START-AFTER-NEXT: Merge contiguous icmps into a memcmp
>>> +; START-AFTER-NEXT: Expand memcmp() to load/stores
>>>
>>>  ; RUN: llc < %s -debug-pass=Structure -start-before=loop-reduce -o
>>> /dev/null 2>&1 | FileCheck %s -check-prefix=START-BEFORE
>>>  ; START-BEFORE: -machine-branch-prob -domtree
>>>  ; START-BEFORE: FunctionPass Manager
>>>  ; START-BEFORE: Loop Strength Reduction
>>> -; START-BEFORE-NEXT: Merge contiguous icmps into a memcmp
>>> +; START-BEFORE-NEXT: Expand memcmp() to load/stores
>>>
>>>  ; RUN: not llc < %s -start-before=nonexistent -o /dev/null 2>&1 |
>>> FileCheck %s -check-prefix=NONEXISTENT-START-BEFORE
>>>  ; RUN: not llc < %s -stop-before=nonexistent -o /dev/null 2>&1 |
>>> FileCheck %s -check-prefix=NONEXISTENT-STOP-BEFORE
>>>
>>> Modified: llvm/trunk/test/CodeGen/PowerPC/memcmp-mergeexpand.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/memcmp-mergeexpand.ll?rev=324319&r1=324318&r2=324319&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/CodeGen/PowerPC/memcmp-mergeexpand.ll (original)
>>> +++ llvm/trunk/test/CodeGen/PowerPC/memcmp-mergeexpand.ll Tue Feb  6
>>> 00:40:18 2018
>>> @@ -7,12 +7,22 @@
>>>
>>>  define zeroext i1 @opeq1(
>>>  ; PPC64LE-LABEL: opeq1:
>>> -; PPC64LE:       # %bb.0: # %opeq1.exit
>>> -; PPC64LE-NEXT:    ld 3, 0(3)
>>> -; PPC64LE-NEXT:    ld 4, 0(4)
>>> -; PPC64LE-NEXT:    xor 3, 3, 4
>>> -; PPC64LE-NEXT:    cntlzd 3, 3
>>> -; PPC64LE-NEXT:    rldicl 3, 3, 58, 63
>>> +; PPC64LE:       # %bb.0: # %entry
>>> +; PPC64LE-NEXT:    lwz 5, 0(3)
>>> +; PPC64LE-NEXT:    lwz 6, 0(4)
>>> +; PPC64LE-NEXT:    cmplw 5, 6
>>> +; PPC64LE-NEXT:    bne 0, .LBB0_2
>>> +; PPC64LE-NEXT:  # %bb.1: # %land.rhs.i
>>> +; PPC64LE-NEXT:    lwz 3, 4(3)
>>> +; PPC64LE-NEXT:    lwz 4, 4(4)
>>> +; PPC64LE-NEXT:    cmpw 3, 4
>>> +; PPC64LE-NEXT:    b .LBB0_3
>>> +; PPC64LE-NEXT:  .LBB0_2:
>>> +; PPC64LE-NEXT:    crxor 2, 2, 2
>>> +; PPC64LE-NEXT:  .LBB0_3: # %opeq1.exit
>>> +; PPC64LE-NEXT:    li 3, 0
>>> +; PPC64LE-NEXT:    li 4, 1
>>> +; PPC64LE-NEXT:    isel 3, 4, 3, 2
>>>  ; PPC64LE-NEXT:    blr
>>>    %"struct.std::pair"* nocapture readonly dereferenceable(8) %a,
>>>    %"struct.std::pair"* nocapture readonly dereferenceable(8) %b)
>>> local_unnamed_addr #0 {
>>>
>>> Modified: llvm/trunk/test/CodeGen/X86/memcmp-mergeexpand.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/memcmp-mergeexpand.ll?rev=324319&r1=324318&r2=324319&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/CodeGen/X86/memcmp-mergeexpand.ll (original)
>>> +++ llvm/trunk/test/CodeGen/X86/memcmp-mergeexpand.ll Tue Feb  6
>>> 00:40:18 2018
>>> @@ -8,22 +8,37 @@
>>>
>>>  define zeroext i1 @opeq1(
>>>  ; X86-LABEL: opeq1:
>>> -; X86:       # %bb.0: # %opeq1.exit
>>> +; X86:       # %bb.0: # %entry
>>>  ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
>>>  ; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
>>>  ; X86-NEXT:    movl (%ecx), %edx
>>> +; X86-NEXT:    cmpl (%eax), %edx
>>> +; X86-NEXT:    jne .LBB0_1
>>> +; X86-NEXT:  # %bb.2: # %land.rhs.i
>>>  ; X86-NEXT:    movl 4(%ecx), %ecx
>>> -; X86-NEXT:    xorl (%eax), %edx
>>> -; X86-NEXT:    xorl 4(%eax), %ecx
>>> -; X86-NEXT:    orl %edx, %ecx
>>> +; X86-NEXT:    cmpl 4(%eax), %ecx
>>>  ; X86-NEXT:    sete %al
>>> +; X86-NEXT:    # kill: def $al killed $al killed $eax
>>> +; X86-NEXT:    retl
>>> +; X86-NEXT:  .LBB0_1:
>>> +; X86-NEXT:    xorl %eax, %eax
>>> +; X86-NEXT:    # kill: def $al killed $al killed $eax
>>>  ; X86-NEXT:    retl
>>>  ;
>>>  ; X64-LABEL: opeq1:
>>> -; X64:       # %bb.0: # %opeq1.exit
>>> -; X64-NEXT:    movq (%rdi), %rax
>>> -; X64-NEXT:    cmpq (%rsi), %rax
>>> +; X64:       # %bb.0: # %entry
>>> +; X64-NEXT:    movl (%rdi), %eax
>>> +; X64-NEXT:    cmpl (%rsi), %eax
>>> +; X64-NEXT:    jne .LBB0_1
>>> +; X64-NEXT:  # %bb.2: # %land.rhs.i
>>> +; X64-NEXT:    movl 4(%rdi), %eax
>>> +; X64-NEXT:    cmpl 4(%rsi), %eax
>>>  ; X64-NEXT:    sete %al
>>> +; X64-NEXT:    # kill: def $al killed $al killed $eax
>>> +; X64-NEXT:    retq
>>> +; X64-NEXT:  .LBB0_1:
>>> +; X64-NEXT:    xorl %eax, %eax
>>> +; X64-NEXT:    # kill: def $al killed $al killed $eax
>>>  ; X64-NEXT:    retq
>>>    %"struct.std::pair"* nocapture readonly dereferenceable(8) %a,
>>>    %"struct.std::pair"* nocapture readonly dereferenceable(8) %b)
>>> local_unnamed_addr #0 {
>>>
>>>
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>>
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