[llvm] r289468 - Recommit r288212: Emit 'no line' information for interesting 'orphan' instructions.
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 16 14:34:08 PST 2016
The use-case that this was derived from is the code that the swift compiler generates for top-level code (In Swift there is no explicit main() function). The user-written code (with line numbers) and the language runtime initialization (compiler-generated, line 0) both end up in the main() function. This is why it starts out with line 0 for the initialization, followed by the code the user wrote with actual line numbers.
-- adrian
> On Dec 16, 2016, at 2:29 PM, Robinson, Paul <paul.robinson at sony.com> wrote:
>
> Sure. I see that the very first debug location is explicitly setting line 0. Is that really what you want?
> --paulr
>
> From: aprantl at apple.com [mailto:aprantl at apple.com]
> Sent: Friday, December 16, 2016 2:00 PM
> To: Robinson, Paul
> Cc: llvm-commits; Saleem Abdulrasool
> Subject: Re: [llvm] r289468 - Recommit r288212: Emit 'no line' information for interesting 'orphan' instructions.
>
> Hi Paul,
>
> we were investigating a test suite regression in the Swift compiler (just in case you are curious: https://bugs.swift.org/browse/SR-3421) that I could bisect down to this commit.
>
> When compiling the attached IR (which I reduced manually from the full testcase) llc now runs into a situation where it never sets the prologue_end flag for the function main().
>
> $llc t.ll -o - | grep '\.loc'
> .loc 1 0 0
> .loc 1 14 13
>
> I assume that this is something we never want to happen. Would you mind taking a look?
>
> -- adrian
>
>
> > On Dec 12, 2016, at 12:49 PM, Paul Robinson via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> >
> > Author: probinson
> > Date: Mon Dec 12 14:49:11 2016
> > New Revision: 289468
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=289468&view=rev
> > Log:
> > Recommit r288212: Emit 'no line' information for interesting 'orphan' instructions.
> >
> > DWARF specifies that "line 0" really means "no appropriate source
> > location" in the line table. By default, use this for branch targets
> > and some other cases that have no specified source location, to
> > prevent inheriting unfortunate line numbers from physically preceding
> > instructions (which might be from completely unrelated source).
> >
> > Updated patch allows enabling or suppressing this behavior for all
> > unspecified source locations.
> >
> > Differential Revision: http://reviews.llvm.org/D24180
> >
> > Added:
> > llvm/trunk/test/DebugInfo/X86/dwarf-no-source-loc.ll
> > Modified:
> > llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
> > llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.h
> > llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> > llvm/trunk/test/CodeGen/X86/stack-protector.ll
> > llvm/trunk/test/CodeGen/X86/unknown-location.ll
> > llvm/trunk/test/DebugInfo/AArch64/line-header.ll
> > llvm/trunk/test/DebugInfo/MIR/X86/no-cfi-loc.mir
> > llvm/trunk/test/DebugInfo/X86/tail-merge.ll
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp Mon Dec 12 14:49:11 2016
> > @@ -200,8 +200,10 @@ void DebugHandlerBase::endInstruction()
> > assert(CurMI != nullptr);
> > // Don't create a new label after DBG_VALUE instructions.
> > // They don't generate code.
> > - if (!CurMI->isDebugValue())
> > + if (!CurMI->isDebugValue()) {
> > PrevLabel = nullptr;
> > + PrevInstBB = CurMI->getParent();
> > + }
> >
> > DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
> > LabelsAfterInsn.find(CurMI);
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.h
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.h?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.h (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DebugHandlerBase.h Mon Dec 12 14:49:11 2016
> > @@ -38,10 +38,12 @@ protected:
> > MachineModuleInfo *MMI;
> >
> > /// Previous instruction's location information. This is used to
> > - /// determine label location to indicate scope boundries in dwarf
> > - /// debug info.
> > + /// determine label location to indicate scope boundaries in debug info.
> > + /// We track the previous instruction's source location (if not line 0),
> > + /// whether it was a label, and its parent BB.
> > DebugLoc PrevInstLoc;
> > MCSymbol *PrevLabel = nullptr;
> > + const MachineBasicBlock *PrevInstBB = nullptr;
> >
> > /// This location indicates end of function prologue and beginning of
> > /// function body.
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Mon Dec 12 14:49:11 2016
> > @@ -62,11 +62,6 @@ static cl::opt<bool>
> > DisableDebugInfoPrinting("disable-debug-info-print", cl::Hidden,
> > cl::desc("Disable debug info printing"));
> >
> > -static cl::opt<bool> UnknownLocations(
> > - "use-unknown-locations", cl::Hidden,
> > - cl::desc("Make an absence of debug location information explicit."),
> > - cl::init(false));
> > -
> > static cl::opt<bool>
> > GenerateGnuPubSections("generate-gnu-dwarf-pub-sections", cl::Hidden,
> > cl::desc("Generate GNU-style pubnames and pubtypes"),
> > @@ -81,6 +76,13 @@ namespace {
> > enum DefaultOnOff { Default, Enable, Disable };
> > }
> >
> > +static cl::opt<DefaultOnOff> UnknownLocations(
> > + "use-unknown-locations", cl::Hidden,
> > + cl::desc("Make an absence of debug location information explicit."),
> > + cl::values(clEnumVal(Default, "At top of block or after label"),
> > + clEnumVal(Enable, "In all cases"), clEnumVal(Disable, "Never")),
> > + cl::init(Default));
> > +
> > static cl::opt<DefaultOnOff>
> > DwarfAccelTables("dwarf-accel-tables", cl::Hidden,
> > cl::desc("Output prototype dwarf accelerator tables."),
> > @@ -1010,31 +1012,73 @@ void DwarfDebug::beginInstruction(const
> > if (MI->isDebugValue() || MI->isCFIInstruction())
> > return;
> > const DebugLoc &DL = MI->getDebugLoc();
> > - if (DL == PrevInstLoc)
> > + // When we emit a line-0 record, we don't update PrevInstLoc; so look at
> > + // the last line number actually emitted, to see if it was line 0.
> > + unsigned LastAsmLine =
> > + Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();
> > +
> > + if (DL == PrevInstLoc) {
> > + // If we have an ongoing unspecified location, nothing to do here.
> > + if (!DL)
> > + return;
> > + // We have an explicit location, same as the previous location.
> > + // But we might be coming back to it after a line 0 record.
> > + if (LastAsmLine == 0 && DL.getLine() != 0) {
> > + // Reinstate the source location but not marked as a statement.
> > + const MDNode *Scope = DL.getScope();
> > + recordSourceLine(DL.getLine(), DL.getCol(), Scope, /*Flags=*/0);
> > + }
> > return;
> > + }
> >
> > if (!DL) {
> > // We have an unspecified location, which might want to be line 0.
> > - if (UnknownLocations) {
> > - PrevInstLoc = DL;
> > - recordSourceLine(0, 0, nullptr, 0);
> > + // If we have already emitted a line-0 record, don't repeat it.
> > + if (LastAsmLine == 0)
> > + return;
> > + // If user said Don't Do That, don't do that.
> > + if (UnknownLocations == Disable)
> > + return;
> > + // See if we have a reason to emit a line-0 record now.
> > + // Reasons to emit a line-0 record include:
> > + // - User asked for it (UnknownLocations).
> > + // - Instruction has a label, so it's referenced from somewhere else,
> > + // possibly debug information; we want it to have a source location.
> > + // - Instruction is at the top of a block; we don't want to inherit the
> > + // location from the physically previous (maybe unrelated) block.
> > + if (UnknownLocations == Enable || PrevLabel ||
> > + (PrevInstBB && PrevInstBB != MI->getParent())) {
> > + // Preserve the file number, if we can, to save space in the line table.
> > + // Do not update PrevInstLoc, it remembers the last non-0 line.
> > + // FIXME: Also preserve the column number, to save more space?
> > + const MDNode *Scope = PrevInstLoc ? PrevInstLoc.getScope() : nullptr;
> > + recordSourceLine(0, 0, Scope, 0);
> > }
> > return;
> > }
> >
> > - // We have a new, explicit location.
> > + // We have an explicit location, different from the previous location.
> > + // Don't repeat a line-0 record, but otherwise emit the new location.
> > + // (The new location might be an explicit line 0, which we do emit.)
> > + if (DL.getLine() == 0 && LastAsmLine == 0)
> > + return;
> > unsigned Flags = 0;
> > - PrevInstLoc = DL;
> > if (DL == PrologEndLoc) {
> > Flags |= DWARF2_FLAG_PROLOGUE_END | DWARF2_FLAG_IS_STMT;
> > PrologEndLoc = DebugLoc();
> > }
> > - if (DL.getLine() !=
> > - Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine())
> > + // If the line changed, we call that a new statement; unless we went to
> > + // line 0 and came back, in which case it is not a new statement.
> > + unsigned OldLine = PrevInstLoc ? PrevInstLoc.getLine() : LastAsmLine;
> > + if (DL.getLine() && DL.getLine() != OldLine)
> > Flags |= DWARF2_FLAG_IS_STMT;
> >
> > const MDNode *Scope = DL.getScope();
> > recordSourceLine(DL.getLine(), DL.getCol(), Scope, Flags);
> > +
> > + // If we're not at line 0, remember this location.
> > + if (DL.getLine())
> > + PrevInstLoc = DL;
> > }
> >
> > static DebugLoc findPrologueEndLoc(const MachineFunction *MF) {
> >
> > Modified: llvm/trunk/test/CodeGen/X86/stack-protector.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/stack-protector.ll?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/stack-protector.ll (original)
> > +++ llvm/trunk/test/CodeGen/X86/stack-protector.ll Mon Dec 12 14:49:11 2016
> > @@ -3888,23 +3888,27 @@ entry:
> > define void @test32() #1 !dbg !7 {
> > entry:
> > ; LINUX-I386-LABEL: test32:
> > -; LINUX-I386: .loc 1 0 0 prologue_end
> > +; LINUX-I386: .loc 1 4 2 prologue_end
> > +; LINUX-I386: .loc 1 0 0
> > ; LINUX-I386-NEXT: calll __stack_chk_fail
> >
> > ; LINUX-X64-LABEL: test32:
> > -; LINUX-X64: .loc 1 0 0 prologue_end
> > +; LINUX-X64: .loc 1 4 2 prologue_end
> > +; LINUX-X64: .loc 1 0 0
> > ; LINUX-X64-NEXT: callq __stack_chk_fail
> >
> > ; LINUX-KERNEL-X64-LABEL: test32:
> > -; LINUX-KERNEL-X64: .loc 1 0 0 prologue_end
> > +; LINUX-KERNEL-X64: .loc 1 4 2 prologue_end
> > +; LINUX-KERNEL-X64: .loc 1 0 0
> > ; LINUX-KERNEL-X64-NEXT: callq __stack_chk_fail
> >
> > ; OPENBSD-AMD64-LABEL: test32:
> > -; OPENBSD-AMD64: .loc 1 0 0 prologue_end
> > +; OPENBSD-AMD64: .loc 1 4 2 prologue_end
> > +; OPENBSD-AMD64: .loc 1 0 0
> > ; OPENBSD-AMD64-NEXT: movl
> > ; OPENBSD-AMD64-NEXT: callq __stack_smash_handler
> > %0 = alloca [5 x i8], align 1
> > - ret void
> > + ret void, !dbg !9
> > }
> >
> > declare double @testi_aux()
> > @@ -3940,3 +3944,4 @@ attributes #5 = { ssp "stack-protector-b
> > !6 = distinct !DISubprogram(name: "__stack_chk_fail", scope: !1, type: !8, unit: !0)
> > !7 = distinct !DISubprogram(name: "test32", scope: !1, type: !8, unit: !0)
> > !8 = !DISubroutineType(types: !2)
> > +!9 = !DILocation(line: 4, column: 2, scope: !7)
> >
> > Modified: llvm/trunk/test/CodeGen/X86/unknown-location.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/unknown-location.ll?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/test/CodeGen/X86/unknown-location.ll (original)
> > +++ llvm/trunk/test/CodeGen/X86/unknown-location.ll Mon Dec 12 14:49:11 2016
> > @@ -1,4 +1,4 @@
> > -; RUN: llc < %s -asm-verbose=false -mtriple=x86_64-apple-darwin10 -use-unknown-locations | FileCheck %s
> > +; RUN: llc < %s -asm-verbose=false -mtriple=x86_64-apple-darwin10 -use-unknown-locations=Enable | FileCheck %s
> >
> > ; The divide instruction does not have a debug location. CodeGen should
> > ; represent this in the debug information. This is done by setting line
> >
> > Modified: llvm/trunk/test/DebugInfo/AArch64/line-header.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/AArch64/line-header.ll?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/test/DebugInfo/AArch64/line-header.ll (original)
> > +++ llvm/trunk/test/DebugInfo/AArch64/line-header.ll Mon Dec 12 14:49:11 2016
> > @@ -3,4 +3,4 @@
> >
> > ; check line table length is correctly calculated for both big and little endian
> > CHECK-LABEL: .debug_line contents:
> > -CHECK: total_length: 0x0000003c
> > +CHECK: total_length: 0x0000003e
> >
> > Modified: llvm/trunk/test/DebugInfo/MIR/X86/no-cfi-loc.mir
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/MIR/X86/no-cfi-loc.mir?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/test/DebugInfo/MIR/X86/no-cfi-loc.mir (original)
> > +++ llvm/trunk/test/DebugInfo/MIR/X86/no-cfi-loc.mir Mon Dec 12 14:49:11 2016
> > @@ -1,6 +1,6 @@
> > # Verify that a CFI instruction with no debug location
> > # does not result in a line-0 location in the assembler.
> > -# RUN: %llc_dwarf -start-after=prologepilog -march=x86-64 -use-unknown-locations %s -o - | FileCheck %s
> > +# RUN: %llc_dwarf -start-after=prologepilog -march=x86-64 -use-unknown-locations=Enable %s -o - | FileCheck %s
> > #
> > # CHECK-NOT: .loc 1 0
> > # CHECK: .cfi_def_cfa_offset
> >
> > Added: llvm/trunk/test/DebugInfo/X86/dwarf-no-source-loc.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/dwarf-no-source-loc.ll?rev=289468&view=auto
> > ==============================================================================
> > --- llvm/trunk/test/DebugInfo/X86/dwarf-no-source-loc.ll (added)
> > +++ llvm/trunk/test/DebugInfo/X86/dwarf-no-source-loc.ll Mon Dec 12 14:49:11 2016
> > @@ -0,0 +1,77 @@
> > +; Verify "no source location" directives appear in appropriate places,
> > +; but don't appear when we explicitly suppress them.
> > +; RUN: llc < %s -o - | FileCheck %s
> > +; RUN: llc < %s -o - -use-unknown-locations=Disable | FileCheck %s --check-prefix=DISABLE
> > +
> > +; Generated from this .cpp targeting linux using -g
> > +; and then removed function attributes as clutter.
> > +;
> > +; void bar(int *);
> > +; void baz(int *);
> > +; # 5 "no-source-loc.cpp"
> > +; void foo(int x) {
> > +; int z;
> > +; if (x)
> > +; # 20 "include.h"
> > +; bar(&z);
> > +; # 10 "no-source-loc.cpp"
> > +; baz(&z);
> > +; }
> > +
> > +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> > +target triple = "x86_64-unknown-linux-gnu"
> > +
> > +; Function Attrs: uwtable
> > +define void @_Z3fooi(i32 %x) !dbg !6 {
> > +entry:
> > + %x.addr = alloca i32, align 4
> > + %z = alloca i32, align 4
> > + store i32 %x, i32* %x.addr, align 4
> > + %0 = load i32, i32* %x.addr, align 4, !dbg !8
> > + %tobool = icmp ne i32 %0, 0, !dbg !8
> > + br i1 %tobool, label %if.then, label %if.end, !dbg !8
> > +
> > +if.then: ; preds = %entry
> > + call void @_Z3barPi(i32* %z), !dbg !9
> > + br label %if.end, !dbg !9
> > +
> > +if.end: ; preds = %if.then, %entry
> > + call void @_Z3bazPi(i32* %z), !dbg !12
> > + ret void, !dbg !14
> > +}
> > +
> > +; CHECK: .loc 1 7 7
> > +; CHECK-NOT: .loc
> > +; CHECK: .loc 1 0 0 is_stmt 0
> > +; CHECK-NOT: .loc
> > +; CHECK: .loc 2 20 5 is_stmt 1
> > +; CHECK: .LBB0_2:
> > +; CHECK-NEXT: .loc 2 0 0 is_stmt 0
> > +; CHECK-NOT: .loc
> > +; CHECK: .loc 1 10 3 is_stmt 1
> > +;
> > +; DISABLE-NOT: .loc 1 0
> > +
> > +declare void @_Z3barPi(i32*)
> > +
> > +declare void @_Z3bazPi(i32*)
> > +
> > +!llvm.dbg.cu = !{!0}
> > +!llvm.module.flags = !{!3, !4}
> > +!llvm.ident = !{!5}
> > +
> > +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 4.0.0 (trunk 278782)", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
> > +!1 = !DIFile(filename: "no-source-loc.cpp", directory: "/tests")
> > +!2 = !{}
> > +!3 = !{i32 2, !"Dwarf Version", i32 4}
> > +!4 = !{i32 2, !"Debug Info Version", i32 3}
> > +!5 = !{!"clang version 4.0.0 (trunk 278782)"}
> > +!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 5, type: !7, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
> > +!7 = !DISubroutineType(types: !2)
> > +!8 = !DILocation(line: 7, column: 7, scope: !6)
> > +!9 = !DILocation(line: 20, column: 5, scope: !10)
> > +!10 = !DILexicalBlockFile(scope: !6, file: !11, discriminator: 0)
> > +!11 = !DIFile(filename: "include.h", directory: "/tests")
> > +!12 = !DILocation(line: 10, column: 3, scope: !13)
> > +!13 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 0)
> > +!14 = !DILocation(line: 11, column: 1, scope: !13)
> >
> > Modified: llvm/trunk/test/DebugInfo/X86/tail-merge.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/tail-merge.ll?rev=289468&r1=289467&r2=289468&view=diff
> > ==============================================================================
> > --- llvm/trunk/test/DebugInfo/X86/tail-merge.ll (original)
> > +++ llvm/trunk/test/DebugInfo/X86/tail-merge.ll Mon Dec 12 14:49:11 2016
> > @@ -1,4 +1,4 @@
> > -; RUN: llc %s -mtriple=x86_64-unknown-unknown -use-unknown-locations=true -o - | FileCheck %s
> > +; RUN: llc %s -mtriple=x86_64-unknown-unknown -use-unknown-locations=Enable -o - | FileCheck %s
> >
> > ; Generated with "clang -gline-tables-only -c -emit-llvm -o - | opt -sroa -S"
> > ; from source:
> >
> >
> > _______________________________________________
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> > llvm-commits at lists.llvm.org
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