[PATCH] D20432: [DAGCombiner] Keep debug information when folding (sext (truncate x)) -> (sextinreg x)

David Blaikie via llvm-commits llvm-commits at lists.llvm.org
Thu May 19 08:08:14 PDT 2016


Generally the test case should just test the optimization - no need to go
all the way through codegen, etc.

what's the current behavior if both instructions have a location?

& why is this in an else if block? Why should it not happen if the ifs
above it are true?

On Thu, May 19, 2016 at 6:57 AM, Marianne Mailhot-Sarrasin via llvm-commits
<llvm-commits at lists.llvm.org> wrote:

> mamai created this revision.
> mamai added a reviewer: probinson.
> mamai added a subscriber: llvm-commits.
> mamai set the repository for this revision to rL LLVM.
>
> In the case that there is a debug value on the truncate instruction and
> none on the sign extend, transfer it from truncate to sign extend so it
> does not get lost. Also adding a test case showing the debug information in
> IR will result in a debug value at code generation.
>
> Repository:
>   rL LLVM
>
> http://reviews.llvm.org/D20432
>
> Files:
>   lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>   test/DebugInfo/ARM/dagcombine-truncate.ll
>
> Index: test/DebugInfo/ARM/dagcombine-truncate.ll
> ===================================================================
> --- /dev/null
> +++ test/DebugInfo/ARM/dagcombine-truncate.ll
> @@ -0,0 +1,44 @@
> +; RUN: llc < %s | FileCheck %s
> +
> +;CHECK: #DEBUG_VALUE: main:bigger
> +
> +; Function Attrs: noinline nounwind
> +define i32 @main() !dbg !4 {
> +entry:
> +  %call = call i32 bitcast (i32 (...)* @max to i32 (i32, i32)*)(i32 1,
> i32 2), !dbg !14
> +  %conv = trunc i32 %call to i8, !dbg !16
> +  call void @llvm.dbg.value(metadata i8 %conv, i64 0, metadata !9,
> metadata !17), !dbg !18
> +  %conv1 = sext i8 %conv to i32, !dbg !19
> +  ret i32 %conv1, !dbg !20
> +}
> +
> +declare i32 @max(...)
> +
> +; Function Attrs: nounwind readnone
> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
> +
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!11, !12}
> +!llvm.ident = !{!13}
> +
> +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer:
> "clang version 3.9.0 (trunk) (http://llvm.org/git/llvm.git
> a0a8cb640e6caead7ea28b9f04a410bc86209e4f)", isOptimized: true,
> runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
> +!1 = !DIFile(filename: "main.c", directory: "/private/tmp")
> +!2 = !{}
> +!3 = !{!4}
> +!4 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 10,
> type: !5, isLocal: false, isDefinition: true, scopeLine: 10, isOptimized:
> true, variables: !8, unit: !0)
> +!5 = !DISubroutineType(types: !6)
> +!6 = !{!7}
> +!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding:
> DW_ATE_signed)
> +!8 = !{!9}
> +!9 = !DILocalVariable(name: "bigger", scope: !4, file: !1, line: 11,
> type: !10)
> +!10 = !DIBasicType(name: "char", size: 8, align: 8, encoding:
> DW_ATE_signed_char)
> +!11 = !{i32 2, !"Dwarf Version", i32 4}
> +!12 = !{i32 2, !"Debug Info Version", i32 3}
> +!13 = !{!"clang version 3.9.0 (trunk) (http://llvm.org/git/llvm.git
> a0a8cb640e6caead7ea28b9f04a410bc86209e4f)"}
> +!14 = !DILocation(line: 11, column: 16, scope: !15)
> +!15 = !DILexicalBlockFile(scope: !4, file: !1, discriminator: 1)
> +!16 = !DILocation(line: 11, column: 16, scope: !4)
> +!17 = !DIExpression()
> +!18 = !DILocation(line: 11, column: 7, scope: !4)
> +!19 = !DILocation(line: 12, column: 9, scope: !4)
> +!20 = !DILocation(line: 12, column: 2, scope: !4)
> Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> ===================================================================
> --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> +++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> @@ -6077,6 +6077,12 @@
>          Op = DAG.getNode(ISD::ANY_EXTEND, SDLoc(N0), VT, Op);
>        else if (OpBits > DestBits)
>          Op = DAG.getNode(ISD::TRUNCATE, SDLoc(N0), VT, Op);
> +      else if (N0->getHasDebugValue() && !N->getHasDebugValue()) {
> +        // Instead of loosing the truncate debug information, pass it to
> N.
> +        N->setDebugLoc(N0->getDebugLoc());
> +        N->setIROrder(N0->getIROrder());
> +        DAG.TransferDbgValues(N0, SDValue(N, 0));
> +      }
>        return DAG.getNode(ISD::SIGN_EXTEND_INREG, SDLoc(N), VT, Op,
>                           DAG.getValueType(N0.getValueType()));
>      }
>
>
>
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