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

Hans Wennborg via llvm-commits llvm-commits at lists.llvm.org
Thu Nov 7 03:38:31 PST 2019


creduced repro:

$ cat /tmp/b.ii
extern "C" int memcmp(void *, void *, long);
struct a {
  int b;
  int c;
  int d;
};
struct e {
  int f;
};
bool operator==(e g, e &h) { return memcmp(&g, &h, sizeof(e)); }
bool operator==(a &g, a &h) { return g.b == h.b && g.c == h.c && g.d == h.d; }
$ bin/clang.bad -cc1 -triple aarch64-unknown-linux-android21 -emit-obj
-fdebug-info-for-profiling -dwarf-column-info
-debug-info-kind=line-tables-only -dwarf-version=4
-debugger-tuning=gdb -Oz -std=c++14 /tmp/b.ii
inlinable function call in a function with debug info must have a !dbg location
  %memcmp = call i32 @memcmp(i8* %cstr, i8* %cstr10, i64 12)
fatal error: error in backend: Broken module found, compilation aborted!

On Thu, Nov 7, 2019 at 10:32 AM Hans Wennborg <hans at chromium.org> wrote:
>
> 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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