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llvm-project/llvm/test/Transforms/BDCE/pr26587.ll

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[BDCE/DebugInfo] Preserve llvm.dbg.value's argument. BDCE has two phases: 1. It asks SimplifyDemandedBits if all the bits of an instruction are dead, and if so, replaces all its uses with the constant zero. 2. Then, it asks SimplifyDemandedBits again if the instruction is really dead (no side effects etc..) and if so, eliminates it. Now, in 1) if all the bits of an instruction are dead, we may end up replacing a dbg use: %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !8, metadata !16), !dbg !17 -> %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !8, metadata !16), !dbg !17 but not eliminating the call because it may have arbitrary side effects. In other words, we lose some debug informations. This patch fixes the problem making sure that BDCE does nothing with the instruction if it has side effects and no non-dbg uses. Differential Revision: https://reviews.llvm.org/D27471 llvm-svn: 288851
2016-12-07 05:52:47 +08:00
; Test that BDCE doesn't destroy llvm.dbg.value's argument.
; RUN: opt -bdce %s -S | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; CHECK: define void @f()
; CHECK-NEXT: entry:
; CHECK-NEXT: tail call void (...) @h()
; CHECK-NEXT: %[[CALL:.*]] = tail call i32 (...) @g()
; CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 %[[CALL:.*]]
define void @f() !dbg !6 {
entry:
tail call void (...) @h(), !dbg !9
%call = tail call i32 (...) @g(), !dbg !10
Remove the obsolete offset parameter from @llvm.dbg.value There is no situation where this rarely-used argument cannot be substituted with a DIExpression and removing it allows us to simplify the DWARF backend. Note that this patch does not yet remove any of the newly dead code. rdar://problem/33580047 Differential Revision: https://reviews.llvm.org/D35951 llvm-svn: 309426
2017-07-29 04:21:02 +08:00
tail call void @llvm.dbg.value(metadata i32 %call, metadata !11, metadata !13), !dbg !14
[BDCE/DebugInfo] Preserve llvm.dbg.value's argument. BDCE has two phases: 1. It asks SimplifyDemandedBits if all the bits of an instruction are dead, and if so, replaces all its uses with the constant zero. 2. Then, it asks SimplifyDemandedBits again if the instruction is really dead (no side effects etc..) and if so, eliminates it. Now, in 1) if all the bits of an instruction are dead, we may end up replacing a dbg use: %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !8, metadata !16), !dbg !17 -> %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !8, metadata !16), !dbg !17 but not eliminating the call because it may have arbitrary side effects. In other words, we lose some debug informations. This patch fixes the problem making sure that BDCE does nothing with the instruction if it has side effects and no non-dbg uses. Differential Revision: https://reviews.llvm.org/D27471 llvm-svn: 288851
2016-12-07 05:52:47 +08:00
tail call void (...) @h(), !dbg !15
ret void, !dbg !16
}
declare void @h(...)
declare i32 @g(...)
Remove the obsolete offset parameter from @llvm.dbg.value There is no situation where this rarely-used argument cannot be substituted with a DIExpression and removing it allows us to simplify the DWARF backend. Note that this patch does not yet remove any of the newly dead code. rdar://problem/33580047 Differential Revision: https://reviews.llvm.org/D35951 llvm-svn: 309426
2017-07-29 04:21:02 +08:00
declare void @llvm.dbg.value(metadata, metadata, metadata)
[BDCE/DebugInfo] Preserve llvm.dbg.value's argument. BDCE has two phases: 1. It asks SimplifyDemandedBits if all the bits of an instruction are dead, and if so, replaces all its uses with the constant zero. 2. Then, it asks SimplifyDemandedBits again if the instruction is really dead (no side effects etc..) and if so, eliminates it. Now, in 1) if all the bits of an instruction are dead, we may end up replacing a dbg use: %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !8, metadata !16), !dbg !17 -> %call = tail call i32 (...) @g() #4, !dbg !15 tail call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !8, metadata !16), !dbg !17 but not eliminating the call because it may have arbitrary side effects. In other words, we lose some debug informations. This patch fixes the problem making sure that BDCE does nothing with the instruction if it has side effects and no non-dbg uses. Differential Revision: https://reviews.llvm.org/D27471 llvm-svn: 288851
2016-12-07 05:52:47 +08:00
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4}
!llvm.ident = !{!5}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "patatino.c", directory: "/home/davide/work/llvm/build-clang/bin")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{!"clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)"}
!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !7, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: false, unit: !0, variables: !2)
!7 = !DISubroutineType(types: !8)
!8 = !{null}
!9 = !DILocation(line: 4, column: 3, scope: !6)
!10 = !DILocation(line: 5, column: 11, scope: !6)
!11 = !DILocalVariable(name: "a", scope: !6, file: !1, line: 5, type: !12)
!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!13 = !DIExpression()
!14 = !DILocation(line: 5, column: 7, scope: !6)
!15 = !DILocation(line: 6, column: 3, scope: !6)
!16 = !DILocation(line: 7, column: 1, scope: !6)