[llvm] a5c8ec4 - [CGDebugInfo] Emit subprograms for decls when AT_tail_call is understood

Thu Nov 7 01:32:32 PST 2019

In Chromium it broke the build in a few configurations, so I've
reverted in 5b9a072c39c.

See https://bugs.chromium.org/p/chromium/issues/detail?id=1022296#c1
for reproducer.

On Thu, Nov 7, 2019 at 3:05 AM Eric Christopher via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
> As a heads up we're starting to see a problem around this commit with
> backtraces for inline functions with msan where the line number has
> gone away (replaced with 0).
>
> Dave is looking at it, but I thought I'd send a message as early as I could.
>
> -eric
>
> On Mon, Nov 4, 2019 at 3:14 PM Vedant Kumar via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
> >
> >
> > Author: Vedant Kumar
> > Date: 2019-11-04T15:14:24-08:00
> > New Revision: a5c8ec4baa2c00d8dbca36ffd236a40f9e0c07ed
> >
> > URL: https://github.com/llvm/llvm-project/commit/a5c8ec4baa2c00d8dbca36ffd236a40f9e0c07ed
> > DIFF: https://github.com/llvm/llvm-project/commit/a5c8ec4baa2c00d8dbca36ffd236a40f9e0c07ed.diff
> >
> > LOG: [CGDebugInfo] Emit subprograms for decls when AT_tail_call is understood
> >
> > Currently, clang emits subprograms for declared functions when the
> > target debugger or DWARF standard is known to support entry values
> > (DW_OP_entry_value & the GNU equivalent).
> >
> > Treat DW_AT_tail_call the same way to allow debuggers to follow cross-TU
> > tail calls.
> >
> > Pre-patch debug session with a cross-TU tail call:
> >
> > ```
> >   * frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
> >     frame #1: 0x0000000100000f99 main`main at a.c:8:10 [opt]
> > ```
> >
> > Post-patch (note that the tail-calling frame, "helper", is visible):
> >
> > ```
> >   * frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
> >     frame #1: 0x0000000100000f80 main`helper [opt] [artificial]
> >     frame #2: 0x0000000100000f99 main`main at a.c:8:10 [opt]
> > ```
> >
> > rdar://46577651
> >
> > Differential Revision: https://reviews.llvm.org/D69743
> >
> > Added:
> >
> >
> > Modified:
> >     clang/lib/CodeGen/CGDebugInfo.cpp
> >     clang/test/CodeGen/debug-info-extern-call.c
> >     clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
> >     llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
> >
> > Removed:
> >
> >
> >
> > ################################################################################
> > diff  --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
> > index e0bb3fda7acf..c0c8fd3c8f16 100644
> > --- a/clang/lib/CodeGen/CGDebugInfo.cpp
> > +++ b/clang/lib/CodeGen/CGDebugInfo.cpp
> > @@ -3748,9 +3748,7 @@ void CGDebugInfo::EmitFunctionDecl(GlobalDecl GD, SourceLocation Loc,
> >  void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
> >                                            QualType CalleeType,
> >                                            const FunctionDecl *CalleeDecl) {
> > -  auto &CGOpts = CGM.getCodeGenOpts();
> > -  if (!CGOpts.EnableDebugEntryValues || !CGM.getLangOpts().Optimize ||
> > -      !CallOrInvoke)
> > +  if (!CallOrInvoke || getCallSiteRelatedAttrs() == llvm::DINode::FlagZero)
> >      return;
> >
> >    auto *Func = CallOrInvoke->getCalledFunction();
> > @@ -4824,10 +4822,10 @@ llvm::DINode::DIFlags CGDebugInfo::getCallSiteRelatedAttrs() const {
> >    bool SupportsDWARFv4Ext =
> >        CGM.getCodeGenOpts().DwarfVersion == 4 &&
> >        (CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::LLDB ||
> > -       (CGM.getCodeGenOpts().EnableDebugEntryValues &&
> > -       CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::GDB));
> > +       CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::GDB);
> >
> > -  if (!SupportsDWARFv4Ext && CGM.getCodeGenOpts().DwarfVersion < 5)
> > +  if (!SupportsDWARFv4Ext && CGM.getCodeGenOpts().DwarfVersion < 5 &&
> > +      !CGM.getCodeGenOpts().EnableDebugEntryValues)
> >      return llvm::DINode::FlagZero;
> >
> >    return llvm::DINode::FlagAllCallsDescribed;
> >
> > diff  --git a/clang/test/CodeGen/debug-info-extern-call.c b/clang/test/CodeGen/debug-info-extern-call.c
> > index e35669b78f93..7f58fe59a635 100644
> > --- a/clang/test/CodeGen/debug-info-extern-call.c
> > +++ b/clang/test/CodeGen/debug-info-extern-call.c
> > @@ -1,8 +1,21 @@
> > -// RUN: %clang -Xclang -femit-debug-entry-values -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - | FileCheck %s -check-prefix=CHECK-EXT
> > -// CHECK-EXT: !DISubprogram(name: "fn1"
> > +// When entry values are emitted, expect a subprogram for extern decls so that
> > +// the dwarf generator can describe call site parameters at extern call sites.
> > +//
> > +// RUN: %clang -Xclang -femit-debug-entry-values -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - | FileCheck %s -check-prefix=ENTRY-VAL
> > +// ENTRY-VAL: !DISubprogram(name: "fn1"
> >
> > -// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -S -emit-llvm %s -o - | FileCheck %s
> > -// CHECK-NOT: !DISubprogram(name: "fn1"
> > +// Similarly, when the debugger tuning is gdb, expect a subprogram for extern
> > +// decls so that the dwarf generator can describe information needed for tail
> > +// call frame reconstrution.
> > +//
> > +// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -ggdb -S -emit-llvm %s -o - | FileCheck %s -check-prefix=GDB
> > +// GDB: !DISubprogram(name: "fn1"
> > +//
> > +// Do not emit a subprogram for extern decls when entry values are disabled and
> > +// the tuning is not set to gdb.
> > +//
> > +// RUN: %clang -g -O2 -target x86_64-none-linux-gnu -gsce -S -emit-llvm %s -o - | FileCheck %s -check-prefix=SCE
> > +// SCE-NOT: !DISubprogram(name: "fn1"
> >
> >  extern int fn1(int a, int b);
> >
> >
> > diff  --git a/clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp b/clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
> > index 1cb2b6c609f3..667c2469b55e 100644
> > --- a/clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
> > +++ b/clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
> > @@ -56,6 +56,7 @@
> >
> >  // NO-ATTR-NOT: FlagAllCallsDescribed
> >
> > +// HAS-ATTR-DAG: DISubprogram(name: "declaration1", {{.*}}, flags: DIFlagPrototyped
> >  // HAS-ATTR-DAG: DISubprogram(name: "declaration2", {{.*}}, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition
> >  // HAS-ATTR-DAG: DISubprogram(name: "struct1", {{.*}}, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
> >  // HAS-ATTR-DAG: DISubprogram(name: "struct1", {{.*}}, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition
> >
> > diff  --git a/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll b/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
> > index c37ce1eb7fbe..33e06faba57b 100644
> > --- a/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
> > +++ b/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll
> > @@ -25,6 +25,14 @@
> >
> >  @sink = global i32 0, align 4, !dbg !0
> >
> > +define void @__has_no_subprogram() {
> > +entry:
> > +  %0 = load volatile i32, i32* @sink, align 4
> > +  %inc = add nsw i32 %0, 1
> > +  store volatile i32 %inc, i32* @sink, align 4
> > +  ret void
> > +}
> > +
> >  ; ASM: DW_TAG_subprogram
> >  ; ASM:   DW_AT_call_all_calls
> >  ; OBJ: [[bat_sp:.*]]: DW_TAG_subprogram
> > @@ -70,6 +78,7 @@ entry:
> >  ; OBJ:     DW_AT_call_tail_call
> >  define void @_Z3foov() !dbg !25 {
> >  entry:
> > +  tail call void @__has_no_subprogram()
> >    tail call void @_Z3barv(), !dbg !26
> >    tail call void @_Z3batv(), !dbg !27
> >    tail call void @_Z3barv(), !dbg !26
> >
> >
> >
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