[llvm-dev] [SelectionDAG] DbgValue nodes aren't transferred
Se Jong Oh via llvm-dev
llvm-dev at lists.llvm.org
Mon Apr 30 13:49:32 PDT 2018
Hi Jonas,
I have another case that DBG_VALUE is not produced. I would appreciate it if you could take a quick look at the testcase below.
test code:
llc -mtriple=aarch64 -stop-after=livedebugvalues -o - test.ll
; Function Attrs: nounwind ssp uwtable
define void @f() #0 !dbg !4 {
entry:
tail call void @h(i16 0) #2, !dbg !14
%call = tail call i16 (...) @g() #2, !dbg !15
tail call void @llvm.dbg.value(metadata i16 %call, metadata !8, metadata !16), !dbg !17
tail call void @h(i16 %call) #2, !dbg !18
ret void, !dbg !19
}
For the second call, the AArch64 ISel lowering produces a 32-bit CopyFromReg from w0.
t18: ch,glue = AArch64ISD::CALL t15, TargetGlobalAddress:i64<i16 (...)* @g> 0, RegisterMask:Untyped, test.c:5:11
t19: ch,glue = callseq_end t18, TargetConstant:i64<0>, TargetConstant:i64<0>, t18:1, test.c:5:11
t20: i32,ch,glue = CopyFromReg t19, Register:i32 $w0, t19:1, test.c:5:11
Then, TargetLowering::LowerCallTo adds a truncate node since the function return type is i16.
t21: i16 = truncate t20, test.c:5:11
When lowering the dbg.value intrinsic, a SDDbgValue node is attached to the truncate since it is the final result of the call.
Lowering the third call constructs any_extend(t21) for the 32-bit register type but optimizes out the truncate node by the following code, and it seems that the DbgValue node on the truncate is also lost.
SelectionDAG::getNode(...)
...
// (ext (trunx x)) -> x
if (OpOpcode == ISD::TRUNCATE) {
SDValue OpOp = Operand.getOperand(0);
if (OpOp.getValueType() == VT)
return OpOp;
}
I am wondering if we can just transfer the dbg node here or we can have a better solution.
The entire test file is here:
; ModuleID = 'test.ll'
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx"
; Function Attrs: nounwind ssp uwtable
define void @f() #0 !dbg !4 {
entry:
tail call void @h(i16 0) #2, !dbg !14
%call = tail call i16 (...) @g() #2, !dbg !15
tail call void @llvm.dbg.value(metadata i16 %call, metadata !8, metadata !16), !dbg !17
tail call void @h(i16 %call) #2, !dbg !18
ret void, !dbg !19
}
declare void @h(i16)
declare i16 @g(...)
; Function Attrs: nounwind readnone
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
attributes #0 = { nounwind ssp uwtable "no-frame-pointer-elim"="true" }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!10, !11, !12}
!llvm.ident = !{!13}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "test.c", directory: "/Volumes/Data/llvm")
!2 = !{}
!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !0, variables: !7)
!5 = !DISubroutineType(types: !6)
!6 = !{null}
!7 = !{!8}
!8 = !DILocalVariable(name: "a", scope: !4, file: !1, line: 5, type: !9)
!9 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
!10 = !{i32 2, !"Dwarf Version", i32 2}
!11 = !{i32 2, !"Debug Info Version", i32 3}
!12 = !{i32 1, !"PIC Level", i32 2}
!13 = !{!"clang version 3.9.0 "}
!14 = !DILocation(line: 4, column: 3, scope: !4)
!15 = !DILocation(line: 5, column: 11, scope: !4)
!16 = !DIExpression()
!17 = !DILocation(line: 5, column: 7, scope: !4)
!18 = !DILocation(line: 6, column: 3, scope: !4)
!19 = !DILocation(line: 7, column: 1, scope: !4)
Thanks,
Sejong
-----Original Message-----
From: jdevlieghere at apple.com <jdevlieghere at apple.com>
Sent: Thursday, March 15, 2018 8:43 AM
To: Se Jong Oh <sejooh at microsoft.com>
Cc: Vedant Kumar <vsk at apple.com>; llvm-dev at lists.llvm.org; Adrian Prantl <aprantl at apple.com>; pidgeot18 at gmail.com
Subject: Re: [llvm-dev] [SelectionDAG] DbgValue nodes aren't transferred
> On Mar 14, 2018, at 7:55 PM, Se Jong Oh <sejooh at microsoft.com> wrote:
>
> Hi Jonas,
>
> Thanks for taking a look! It makes linear-dbg-value.ll pass for my target by producing DEBUG_VALUEs correctly. I also tried a simple function with few operations and confirmed DEBUG_VALUEs which are not produced without trasferDbgValues in SetPromotedInteger.
That’s great news! Do you plan on creating a patch for this upstream?
>
> Thanks,
> Sejong
>
> From: jdevlieghere at apple.com <jdevlieghere at apple.com>
> Sent: Wednesday, March 14, 2018 4:07 AM
> To: Se Jong Oh <sejooh at microsoft.com>
> Cc: Vedant Kumar <vsk at apple.com>; llvm-dev at lists.llvm.org; Adrian Prantl <aprantl at apple.com>; pidgeot18 at gmail.com
> Subject: Re: [llvm-dev] [SelectionDAG] DbgValue nodes aren't transferred
>
> Hi Sejong,
>
> Indeed, I think you are right and we should call transferDbgValues in SetPromotedInteger.
>
> I couldn’t immediately find a suitable in-tree test to verify this though. Can you check and let me know whether this works for your target?
>
> Thanks,
> Jonas
>
>
> On Mar 13, 2018, at 7:45 PM, Se Jong Oh <sejooh at microsoft.com> wrote:
>
> Thanks for help! I think that sign extension is not involved here. PromoteIntegerResult is called since i32 is not a legal type in my target and the legalizer promotes operations with i32 result type to i64 operations. I think that SetPromotedInteger seems to be a common place for all promotions like SetExpandedInteger.
>
> Jonas, I would appreciate it if you can guide me about whether my understanding is correct or not.
>
> Thanks,
> Sejong
>
>
>
> From: vsk at apple.com <vsk at apple.com>
> Sent: Friday, March 9, 2018 3:19 PM
> To: Se Jong Oh <sejooh at microsoft.com>
> Cc: llvm-dev at lists.llvm.org; Jonas Devlieghere <jdevlieghere at apple.com>; Adrian Prantl <aprantl at apple.com>; pidgeot18 at gmail.com
> Subject: Re: [llvm-dev] [SelectionDAG] DbgValue nodes aren't transferred
>
> + Adrian, Joshua
> + Jonas, since he contributed the transferDbgValues change in DAGTypeLegalizer::SetExpandedInteger
>
> On Mar 8, 2018, at 5:44 PM, Se Jong Oh via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>
> Hi,
>
> I have a problem that dbg_value nodes are not transferred when integer DAG nodes are promoted. For example, an i32 add node is promoted to a i64 add node by DAGTypeLegalizer::PromoteIntegerResult and its dbg_value node is not transferred to the new node.
>
> t9: i32 = add nsw t5, t8 à t31: i64 = add t30, t7 ; the dbg_value node is not transferred to the new i64 add node.
>
> For expansion, DAGTypeLegalizer::SetExpandedInteger calls transferDbgValues() but I couldn’t find any place to call trasnferDbgValues() for integer type promotion in DAGTypeLegalizer ::SetPromotedInteger and other places.
>
> Maybe the right place to do this is within the PromoteIntRes_ helper for sign extensions?
>
> best,
> vedant
>
>
>
> I am wondering If I miss anything or the legalization needs to call transferDbgValues() for this case.
>
> I found this problem because a recently added unittest, DebugInfo/X86/linear-dbg-value.ll fails for my project, and the x86 and aarch64 backends don’t have this problem since they don’t promote i32 add nodes.
>
> Thanks,
> Sejong
>
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