[DebugInfo] Avoid generating DW_TAG_GNU_call_site if no DW_TAG_GNU_call_site_parameter present

[alok]

Summary

There are conditions when DW_TAG_GNU_call_site is generated which has
no child of tag DW_TAG_GNU_call_site_parameter. This information does
not help and only contributes to incresed size of DWARF info.
Below is the test program.
```````````````````````````
subroutine fun (array)
  integer :: array (*)

  array(5:10) = 1311
  array(7) = 1
  array(100) = 100
  return
end subroutine

program vla
  interface
    subroutine fun (array)
      integer :: array (*)
    end subroutine
  end interface
  integer :: sub_arr(42)

  sub_arr(:) = 3
  call fun(sub_arr)
end program vla
```````````````````````````
which produces,
0x00000060:     DW_TAG_GNU_call_site
                  DW_AT_abstract_origin (0x00000088 "fun")
                  DW_AT_low_pc  (0x000000000000007a)

0x0000006d:     NULL
```````````````````````````

[djtodoro]

Actually, the call_site DIE is being used for printing artificial frames for tail calls...

[alok]

In D99709#2663302, @djtodoro wrote:

Actually, the call_site DIE is being used for printing artificial frames for tail calls...

Thanks for this info. I was not aware of it.

[djtodoro]

I think some LLDB tests would fail for sure...

[dblaikie]

In D99709#2663321, @djtodoro wrote:

I think some LLDB tests would fail for sure...

Is there LLVM test coverage for this? If not it'd be good to make sure some is added.

[djtodoro]

In D99709#2671762, @dblaikie wrote:

In D99709#2663321, @djtodoro wrote:

I think some LLDB tests would fail for sure...

Is there LLVM test coverage for this? If not it'd be good to make sure some is added.

There are (the premerge also shows it). By applying this patch we have:

Failed Tests:
LLVM :: CodeGen/X86/xray-custom-log.ll
LLVM :: DebugInfo/AArch64/unretained-declaration-subprogram.ll
LLVM :: DebugInfo/MIR/ARM/call-site-info-vmovd.mir
LLVM :: DebugInfo/MIR/ARM/call-site-info-vmovs.mir
LLVM :: DebugInfo/MIR/Hexagon/bundled-call-pr44001.mir
LLVM :: DebugInfo/MIR/X86/call-site-gnu-vs-dwarf5-attrs.mir
LLVM :: DebugInfo/MIR/X86/debug-call-site-param.mir
LLVM :: DebugInfo/X86/convert-loclist.ll
LLVM :: DebugInfo/X86/dbg-call-site-undef-params.ll
LLVM :: DebugInfo/X86/debug_addr.ll
LLVM :: DebugInfo/X86/dwarf-callsite-related-attrs.ll
LLVM :: DebugInfo/X86/fission-call-site.ll
LLVM :: DebugInfo/X86/lto-cross-cu-call-origin-ref.ll
LLVM :: DebugInfo/X86/ranges_always.ll
LLVM :: tools/llvm-dwarfdump/X86/stats-dbg-callsite-info.ll

[dblaikie]

In D99709#2673316, @djtodoro wrote:

In D99709#2671762, @dblaikie wrote:

In D99709#2663321, @djtodoro wrote:

I think some LLDB tests would fail for sure...

Is there LLVM test coverage for this? If not it'd be good to make sure some is added.

There are (the premerge also shows it). By applying this patch we have:

Failed Tests:
LLVM :: CodeGen/X86/xray-custom-log.ll
LLVM :: DebugInfo/AArch64/unretained-declaration-subprogram.ll
LLVM :: DebugInfo/MIR/ARM/call-site-info-vmovd.mir
LLVM :: DebugInfo/MIR/ARM/call-site-info-vmovs.mir
LLVM :: DebugInfo/MIR/Hexagon/bundled-call-pr44001.mir
LLVM :: DebugInfo/MIR/X86/call-site-gnu-vs-dwarf5-attrs.mir
LLVM :: DebugInfo/MIR/X86/debug-call-site-param.mir
LLVM :: DebugInfo/X86/convert-loclist.ll
LLVM :: DebugInfo/X86/dbg-call-site-undef-params.ll
LLVM :: DebugInfo/X86/debug_addr.ll
LLVM :: DebugInfo/X86/dwarf-callsite-related-attrs.ll
LLVM :: DebugInfo/X86/fission-call-site.ll
LLVM :: DebugInfo/X86/lto-cross-cu-call-origin-ref.ll
LLVM :: DebugInfo/X86/ranges_always.ll
LLVM :: tools/llvm-dwarfdump/X86/stats-dbg-callsite-info.ll

Ah, great!

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

for (const MachineInstr &MI : MBB.instrs()) {
 
       // For tail calls, it's necessary to record the address of the branch
       // instruction so that the debugger can show where the tail call occurred.
       const MCSymbol *CallAddr =
           IsTail ? getLabelBeforeInsn(TopLevelCallMI) : nullptr;
 
       assert((IsTail || PCAddr) && "Non-tail call without return PC");
 
+      ParamSet Params;
+      // Try to interpret values of call site parameters.
+      if (!emitDebugEntryValues())
+        continue;
+
+      collectCallSiteParameters(&MI, Params);
+
+      if (Params.size() == 0)
+        continue;
+
       LLVM_DEBUG(dbgs() << "CallSiteEntry: " << MF.getName() << " -> "
                         << (CalleeDecl ? CalleeDecl->getName()
                                        : StringRef(MF.getSubtarget()
                                                        .getRegisterInfo()
                                                        ->getName(CallReg)))
                         << (IsTail ? " [IsTail]" : "") << "\n");
 
       DIE &CallSiteDIE = CU.constructCallSiteEntryDIE(
           ScopeDIE, CalleeDIE, IsTail, PCAddr, CallAddr, CallReg);
 
-      // Optionally emit call-site-param debug info.
-      if (emitDebugEntryValues()) {
-        ParamSet Params;
-        // Try to interpret values of call site parameters.
-        collectCallSiteParameters(&MI, Params);
-        CU.constructCallSiteParmEntryDIEs(CallSiteDIE, Params);
-      }
-    }
-  }
-}
 
 void DwarfDebug::addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const {
   if (!U.hasDwarfPubSections())
     return;
 
   U.addFlag(D, dwarf::DW_AT_GNU_pubnames);
 }
 

llvm/test/DebugInfo/X86/dwarf-empty_callsite.ll

+;; Check DW_TAG_GNU_call_site without DW_TAG_GNU_call_site_parameter is not created.
+; REQUIRES: x86_64-linux
+
+; RUN: llc -emit-call-site-info -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s
+
+; CHECK-NOT: DW_TAG_GNU_call_site
+
+;; The IR is generated from below source program
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;subroutine fun (array)
+;;  integer :: array (*)
+;;
+;;  array(5:10) = 1311
+;;  array(7) = 1
+;;  array(100) = 100
+;;  return
+;;end subroutine
+;;
+;;program vla
+;;  interface
+;;    subroutine fun (array)
+;;      integer :: array (*)
+;;    end subroutine
+;;  end interface
+;;  integer :: sub_arr(42)
+;;
+;;  sub_arr(:) = 3
+;;  call fun(sub_arr)
+;;end program vla
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+; ModuleID = '/tmp/empty_callsite.ll'
+source_filename = "/tmp/empty_callsite.ll"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.BSS2 = type <{ [168 x i8] }>
+
+@.BSS2 = internal global %struct.BSS2 zeroinitializer, align 32, !dbg !0
+@.C330_MAIN_ = internal constant i32 0
+
+; Function Attrs: nofree norecurse nounwind writeonly
+define void @fun_(i64* noalias nocapture %array) local_unnamed_addr !dbg !15 {
+L.entry:
+  call void @llvm.dbg.declare(metadata i64* %array, metadata !21, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i64 5, metadata !23, metadata !DIExpression()), !dbg !22
+  %0 = bitcast i64* %array to i8*
+  %1 = getelementptr i8, i8* %0, i64 -4
+  %2 = bitcast i8* %1 to i32*
+  br label %L.LB1_362
+
+L.LB1_362:                                        ; preds = %L.LB1_362, %L.entry
+  %"i$a_360.0" = phi i64 [ 5, %L.entry ], [ %4, %L.LB1_362 ], !dbg !25
+  call void @llvm.dbg.value(metadata i64 %"i$a_360.0", metadata !23, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i64 %"i$a_360.0", metadata !26, metadata !DIExpression()), !dbg !22
+  %3 = getelementptr i32, i32* %2, i64 %"i$a_360.0", !dbg !25
+  store i32 1311, i32* %3, align 4, !dbg !25
+  call void @llvm.dbg.value(metadata i64 %"i$a_360.0", metadata !27, metadata !DIExpression()), !dbg !22
+  %4 = add nuw nsw i64 %"i$a_360.0", 1, !dbg !25
+  call void @llvm.dbg.value(metadata i64 %4, metadata !23, metadata !DIExpression()), !dbg !22
+  %exitcond.not = icmp eq i64 %4, 11, !dbg !25
+  br i1 %exitcond.not, label %L.LB1_387, label %L.LB1_362, !dbg !25
+
+L.LB1_387:                                        ; preds = %L.LB1_362
+  %5 = getelementptr i64, i64* %array, i64 3, !dbg !28
+  %6 = bitcast i64* %5 to i32*, !dbg !28
+  store i32 1, i32* %6, align 4, !dbg !28
+  %7 = getelementptr i8, i8* %0, i64 396, !dbg !29
+  %8 = bitcast i8* %7 to i32*, !dbg !29
+  store i32 100, i32* %8, align 4, !dbg !29
+  ret void, !dbg !30
+}
+
+define void @MAIN_() local_unnamed_addr !dbg !2 {
+L.entry:
+  call void (i8*, ...) bitcast (void (...)* @fort_init to void (i8*, ...)*)(i8* bitcast (i32* @.C330_MAIN_ to i8*))
+  call void @llvm.dbg.value(metadata i64 1, metadata !31, metadata !DIExpression()), !dbg !32
+  br label %L.LB2_359
+
+L.LB2_359:                                        ; preds = %L.LB2_359, %L.entry
+  %"i$a_356.0" = phi i64 [ 1, %L.entry ], [ %1, %L.LB2_359 ], !dbg !33
+  call void @llvm.dbg.value(metadata i64 %"i$a_356.0", metadata !31, metadata !DIExpression()), !dbg !32
+  call void @llvm.dbg.value(metadata i64 %"i$a_356.0", metadata !34, metadata !DIExpression()), !dbg !32
+  %0 = getelementptr i32, i32* bitcast (i8* getelementptr (i8, i8* getelementptr inbounds (%struct.BSS2, %struct.BSS2* @.BSS2, i64 0, i32 0, i64 0), i64 -4) to i32*), i64 %"i$a_356.0", !dbg !33
+  store i32 3, i32* %0, align 4, !dbg !33
+  call void @llvm.dbg.value(metadata i64 %"i$a_356.0", metadata !35, metadata !DIExpression()), !dbg !32
+  %1 = add nuw nsw i64 %"i$a_356.0", 1, !dbg !33
+  call void @llvm.dbg.value(metadata i64 %1, metadata !31, metadata !DIExpression()), !dbg !32
+  %exitcond.not = icmp eq i64 %1, 43, !dbg !33
+  br i1 %exitcond.not, label %L.LB2_376, label %L.LB2_359, !dbg !33
+
+L.LB2_376:                                        ; preds = %L.LB2_359
+  call void @fun_(i64* bitcast (%struct.BSS2* @.BSS2 to i64*)), !dbg !36
+  ret void, !dbg !37
+}
+
+declare void @fort_init(...) local_unnamed_addr
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.module.flags = !{!13, !14}
+!llvm.dbg.cu = !{!4}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "sub_arr", linkageName: ".BSS2", scope: !2, file: !3, line: 16, type: !9, isLocal: true, isDefinition: true)
+!2 = distinct !DISubprogram(name: "vla", scope: !4, file: !3, line: 10, type: !7, scopeLine: 10, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized | DISPFlagMainSubprogram, unit: !4)
+!3 = !DIFile(filename: "empty_callsite.f90", directory: "/home/alok/openllvm/llvm-project_2/build.shared.d")
+!4 = distinct !DICompileUnit(language: DW_LANG_Fortran90, file: !3, producer: " F90 Flang - 1.5 2017-05-01", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !5, globals: !6, imports: !5, nameTableKind: None)
+!5 = !{}
+!6 = !{!0}
+!7 = !DISubroutineType(cc: DW_CC_program, types: !8)
+!8 = !{null}
+!9 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 1344, align: 32, elements: !11)
+!10 = !DIBasicType(name: "integer", size: 32, align: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DISubrange(lowerBound: 1, upperBound: 42)
+!13 = !{i32 2, !"Dwarf Version", i32 4}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = distinct !DISubprogram(name: "fun", scope: !4, file: !3, line: 1, type: !16, scopeLine: 1, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !4)
+!16 = !DISubroutineType(types: !17)
+!17 = !{null, !18}
+!18 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, align: 32, elements: !19)
+!19 = !{!20}
+!20 = !DISubrange(lowerBound: 1)
+!21 = !DILocalVariable(name: "array", arg: 1, scope: !15, file: !3, line: 1, type: !18)
+!22 = !DILocation(line: 0, scope: !15)
+!23 = distinct !DILocalVariable(scope: !15, file: !3, line: 4, type: !24, flags: DIFlagArtificial)
+!24 = !DIBasicType(name: "integer*8", size: 64, align: 64, encoding: DW_ATE_signed)
+!25 = !DILocation(line: 4, column: 1, scope: !15)
+!26 = distinct !DILocalVariable(scope: !15, file: !3, line: 4, type: !24, flags: DIFlagArtificial)
+!27 = distinct !DILocalVariable(scope: !15, file: !3, line: 4, type: !24, flags: DIFlagArtificial)
+!28 = !DILocation(line: 5, column: 1, scope: !15)
+!29 = !DILocation(line: 6, column: 1, scope: !15)
+!30 = !DILocation(line: 8, column: 1, scope: !15)
+!31 = distinct !DILocalVariable(scope: !2, file: !3, line: 18, type: !24, flags: DIFlagArtificial)
+!32 = !DILocation(line: 0, scope: !2)
+!33 = !DILocation(line: 18, column: 1, scope: !2)
+!34 = distinct !DILocalVariable(scope: !2, file: !3, line: 18, type: !24, flags: DIFlagArtificial)
+!35 = distinct !DILocalVariable(scope: !2, file: !3, line: 18, type: !24, flags: DIFlagArtificial)
+!36 = !DILocation(line: 19, column: 1, scope: !2)
+!37 = !DILocation(line: 20, column: 1, scope: !2)