[llvm] r224126 - Reapply "[MachineScheduler] Fix for PR21807: minor code difference building with/without -g."
Andrea Di Biagio
andrea.dibiagio at gmail.com
Fri Dec 12 10:30:34 PST 2014
On Fri, Dec 12, 2014 at 5:52 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Fri, Dec 12, 2014 at 7:09 AM, Andrea Di Biagio
> <Andrea_DiBiagio at sn.scee.net> wrote:
>>
>> Author: adibiagio
>> Date: Fri Dec 12 09:09:58 2014
>> New Revision: 224126
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=224126&view=rev
>> Log:
>> Reapply "[MachineScheduler] Fix for PR21807: minor code difference
>> building with/without -g."
>>
>> This reapplies r224118 with a fix for test
>> 'misched-code-difference-with-debug.ll'.
>> That test was failing on some buildbots because it was x86 specific but it
>> was
>> missing a target triple.
>> Added an explicit triple to test misched-code-difference-with-debug.ll.
>>
>> Added:
>> llvm/trunk/test/CodeGen/X86/misched-code-difference-with-debug.ll
>> Modified:
>> llvm/trunk/lib/CodeGen/MachineScheduler.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/MachineScheduler.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineScheduler.cpp?rev=224126&r1=224125&r2=224126&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/MachineScheduler.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/MachineScheduler.cpp Fri Dec 12 09:09:58 2014
>> @@ -430,9 +430,11 @@ void MachineSchedulerBase::scheduleRegio
>> // instruction stream until we find the nearest boundary.
>> unsigned NumRegionInstrs = 0;
>> MachineBasicBlock::iterator I = RegionEnd;
>> - for(;I != MBB->begin(); --I, --RemainingInstrs, ++NumRegionInstrs)
>> {
>> + for(;I != MBB->begin(); --I, --RemainingInstrs) {
>> if (isSchedBoundary(std::prev(I), MBB, MF, TII, IsPostRA))
>> break;
>> + if (!I->isDebugValue())
>> + ++NumRegionInstrs;
>> }
>> // Notify the scheduler of the region, even if we may skip
>> scheduling
>> // it. Perhaps it still needs to be bundled.
>>
>> Added: llvm/trunk/test/CodeGen/X86/misched-code-difference-with-debug.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/misched-code-difference-with-debug.ll?rev=224126&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/CodeGen/X86/misched-code-difference-with-debug.ll
>> (added)
>> +++ llvm/trunk/test/CodeGen/X86/misched-code-difference-with-debug.ll Fri
>> Dec 12 09:09:58 2014
>> @@ -0,0 +1,90 @@
>> +; RUN: llc < %s -march=x86-64 -mtriple=x86_64-unknown-unknown
>> -mcpu=generic | FileCheck %s
>> +; Both functions should produce the same code. The presence of debug
>> values
>> +; should not affect the scheduling strategy.
>> +; Generated from:
>> +; char argc;
>> +; class C {
>> +; public:
>> +; int test(char ,char ,char ,...);
>> +; };
>> +; void foo() {
>> +; C c;
>> +; char lc = argc;
>> +; c.test(0,argc,0,lc);
>> +; c.test(0,argc,0,lc);
>> +; }
>
>
> Is this a minimal reproduction? I'm slightly surprised at some of the quirks
> here, and it might be best to at least highlight the bits that make this
> interesting (I assume it's not important that this is a non-static member
> function, for example - it might just need an extra argument (add another
> char argument and make it a free function, removing the class C)). Does argc
> need to be copied like that, or could 'lc' just be another (possibly local)
> variable (maybe it needs to not be optimzed away, in which case a global
> might be the simplest)? Does 'argc' have to appear between two other zeros
> like that? etc...
>
> Anyawy, would be nice to ensure the test case is fully reduced - just
> checking.
Hi David,
As far as I understand, the only constraint is that the number of
instructions in a scheduling region (including dbg.values) has to be
above a certain threshold to trigger the change in behavior in the
scheduler.
I remember that Russ (the author of this test) tried to obtain a
minimal reproducible. However, I think you are right and this test can
probably be further simplified. I will ask him to have a look at see
if it can be further reduced.
Thanks,
Andrea
>
>>
>> +;
>> +; with
>> +; clang -O2 -c test.cpp -emit-llvm -S
>> +; clang -O2 -c test.cpp -emit-llvm -S -g
>> +;
>> +
>> +
>> +%class.C = type { i8 }
>> +
>> + at argc = global i8 0, align 1
>> +
>> +declare i32 @test_function(%class.C*, i8 signext, i8 signext, i8 signext,
>> ...)
>> +
>> +; CHECK-LABEL: test_without_debug
>> +; CHECK: movl [[A:%[a-z]+]], [[B:%[a-z]+]]
>> +; CHECK-NEXT: movl [[A]], [[C:%[a-z]+]]
>> +define void @test_without_debug() {
>> +entry:
>> + %c = alloca %class.C, align 1
>> + %0 = load i8* @argc, align 1
>> + %conv = sext i8 %0 to i32
>> + %call = call i32 (%class.C*, i8, i8, i8, ...)* @test_function(%class.C*
>> %c, i8 signext 0, i8 signext %0, i8 signext 0, i32 %conv)
>> + %1 = load i8* @argc, align 1
>> + %call2 = call i32 (%class.C*, i8, i8, i8, ...)*
>> @test_function(%class.C* %c, i8 signext 0, i8 signext %1, i8 signext 0, i32
>> %conv)
>> + ret void
>> +}
>> +
>> +; CHECK-LABEL: test_with_debug
>> +; CHECK: movl [[A]], [[B]]
>> +; CHECK-NEXT: movl [[A]], [[C]]
>> +define void @test_with_debug() {
>> +entry:
>> + %c = alloca %class.C, align 1
>> + %0 = load i8* @argc, align 1
>> + tail call void @llvm.dbg.value(metadata !{i8 %0}, i64 0, metadata !19,
>> metadata !29)
>> + %conv = sext i8 %0 to i32
>> + tail call void @llvm.dbg.value(metadata !{%class.C* %c}, i64 0,
>> metadata !18, metadata !29)
>> + %call = call i32 (%class.C*, i8, i8, i8, ...)* @test_function(%class.C*
>> %c, i8 signext 0, i8 signext %0, i8 signext 0, i32 %conv)
>> + %1 = load i8* @argc, align 1
>> + call void @llvm.dbg.value(metadata !{%class.C* %c}, i64 0, metadata
>> !18, metadata !29)
>> + %call2 = call i32 (%class.C*, i8, i8, i8, ...)*
>> @test_function(%class.C* %c, i8 signext 0, i8 signext %1, i8 signext 0, i32
>> %conv)
>> + ret void
>> +}
>> +
>> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
>> +
>> +!llvm.dbg.cu = !{!0}
>> +!llvm.module.flags = !{!22, !23}
>> +
>> +!0 = metadata !{metadata !"", metadata !1, metadata !2, metadata !3,
>> metadata !12, metadata !20, metadata !2} ; [ DW_TAG_compile_unit ]
>> [test.cpp] [DW_LANG_C_plus_plus]
>> +!1 = metadata !{metadata !"test.cpp", metadata !""}
>> +!2 = metadata !{}
>> +!3 = metadata !{metadata !4}
>> +!4 = metadata !{metadata !"0x2\00C\002\008\008\000\000\000", metadata !1,
>> null, null, metadata !5, null, null, metadata !"_ZTS1C"} ; [
>> DW_TAG_class_type ] [C] [line 2, size 8, align 8, offset 0] [def] [from ]
>> +!5 = metadata !{metadata !6}
>> +!6 = metadata !{metadata !"", metadata !1, metadata !"_ZTS1C", metadata
>> !7, null, null, null, null, null} ; [ DW_TAG_subprogram ] [line 4] [public]
>> [test]
>> +!7 = metadata !{metadata !"", null, null, null, metadata !8, null, null,
>> null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from
>> ]
>> +!8 = metadata !{metadata !9, metadata !10, metadata !11, metadata !11,
>> metadata !11, null}
>> +!9 = metadata !{metadata !"", null, null} ; [ DW_TAG_base_type ] [int]
>> [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
>> +!10 = metadata !{metadata !"", null, null, metadata !"_ZTS1C"} ; [
>> DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [artificial]
>> [from _ZTS1C]
>> +!11 = metadata !{metadata !"0x24\00char\000\008\008\000\000\006", null,
>> null} ; [ DW_TAG_base_type ] [char] [line 0, size 8, align 8, offset 0, enc
>> DW_ATE_signed_char]
>> +!12 = metadata !{metadata !13}
>> +!13 = metadata !{metadata
>> !"0x2e\00test_with_debug\00test_with_debug\00test_with_debug\006\000\001\000\000\00256\001\006",
>> metadata !1, metadata !14, metadata !15, null, void ()* @test_with_debug,
>> null, null, metadata !17} ; [ DW_TAG_subprogram ] [line 6] [def]
>> [test_with_debug]
>> +!14 = metadata !{metadata !"0x29", metadata !1}
>> +!15 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null,
>> null, metadata !16, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0,
>> size 0, align 0, offset 0] [from ]
>> +!16 = metadata !{null}
>> +!17 = metadata !{metadata !18, metadata !19}
>> +!18 = metadata !{metadata !"0x100\00c\007\000", metadata !13, metadata
>> !14, metadata !"_ZTS1C"} ; [ DW_TAG_auto_variable ] [c] [line 7]
>> +!19 = metadata !{metadata !"0x100\00lc\008\000", metadata !13, metadata
>> !14, metadata !11} ; [ DW_TAG_auto_variable ] [lc] [line 8]
>> +!20 = metadata !{metadata !21}
>> +!21 = metadata !{metadata !"0x34\00argc\00argc\00\001\000\001", null,
>> metadata !14, metadata !11, i8* @argc, null} ; [ DW_TAG_variable ] [argc]
>> [line 1] [def]
>> +!22 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
>> +!23 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
>> +!25 = metadata !{i32 8, i32 3, metadata !13, null}
>> +!29 = metadata !{metadata !"0x102"} ; [ DW_TAG_expression ]
>>
>>
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