[llvm] r310014 - Teach GlobalSRA to update the debug info for split-up globals.

Adrian Prantl via llvm-commits llvm-commits at lists.llvm.org
Thu Aug 3 18:19:54 PDT 2017


Author: adrian
Date: Thu Aug  3 18:19:54 2017
New Revision: 310014

URL: http://llvm.org/viewvc/llvm-project?rev=310014&view=rev
Log:
Teach GlobalSRA to update the debug info for split-up globals.

This is similar to what we are doing in "regular" SROA and creates
DW_OP_LLVM_fragment operations to describe the resulting variables.

rdar://problem/33654891

Added:
    llvm/trunk/test/DebugInfo/Generic/global-sra-array.ll
    llvm/trunk/test/DebugInfo/Generic/global-sra-struct.ll
Modified:
    llvm/trunk/include/llvm/IR/DIBuilder.h
    llvm/trunk/lib/IR/DIBuilder.cpp
    llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp

Modified: llvm/trunk/include/llvm/IR/DIBuilder.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/DIBuilder.h?rev=310014&r1=310013&r2=310014&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/DIBuilder.h (original)
+++ llvm/trunk/include/llvm/IR/DIBuilder.h Thu Aug  3 18:19:54 2017
@@ -551,13 +551,17 @@ namespace llvm {
     DIExpression *createExpression(ArrayRef<uint64_t> Addr = None);
     DIExpression *createExpression(ArrayRef<int64_t> Addr);
 
-    /// Create a descriptor to describe one part
-    /// of aggregate variable that is fragmented across multiple Values.
+    /// Create a descriptor to describe one part of an aggregate variable that
+    /// is fragmented across multiple Values. The DW_OP_LLVM_fragment operation
+    /// will be appended to the elements of \c Expr. If \c Expr already contains
+    /// a \c DW_OP_LLVM_fragment \c OffsetInBits is interpreted as an offset
+    /// into the existing fragment.
     ///
     /// \param OffsetInBits Offset of the piece in bits.
     /// \param SizeInBits   Size of the piece in bits.
     DIExpression *createFragmentExpression(unsigned OffsetInBits,
-                                           unsigned SizeInBits);
+                                           unsigned SizeInBits,
+                                           const DIExpression *Expr = nullptr);
 
     /// Create an expression for a variable that does not have an address, but
     /// does have a constant value.

Modified: llvm/trunk/lib/IR/DIBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DIBuilder.cpp?rev=310014&r1=310013&r2=310014&view=diff
==============================================================================
--- llvm/trunk/lib/IR/DIBuilder.cpp (original)
+++ llvm/trunk/lib/IR/DIBuilder.cpp Thu Aug  3 18:19:54 2017
@@ -668,10 +668,31 @@ DIExpression *DIBuilder::createExpressio
   return createExpression(Addr);
 }
 
-DIExpression *DIBuilder::createFragmentExpression(unsigned OffsetInBytes,
-                                                  unsigned SizeInBytes) {
-  uint64_t Addr[] = {dwarf::DW_OP_LLVM_fragment, OffsetInBytes, SizeInBytes};
-  return DIExpression::get(VMContext, Addr);
+DIExpression *DIBuilder::createFragmentExpression(unsigned OffsetInBits,
+                                                  unsigned SizeInBits,
+                                                  const DIExpression *Expr) {
+  SmallVector<uint64_t, 8> Ops;
+  // Copy over the expression, but leave off any trailing DW_OP_LLVM_fragment.
+  if (Expr) {
+    for (auto Op : Expr->expr_ops()) {
+      if (Op.getOp() == dwarf::DW_OP_LLVM_fragment) {
+        // Make the new offset point into the existing fragment.
+        uint64_t FragmentOffsetInBits = Op.getArg(0);
+        uint64_t FragmentSizeInBits = Op.getArg(1);
+        assert((OffsetInBits + SizeInBits <= FragmentSizeInBits) &&
+               "new fragment outside of original fragment");
+        OffsetInBits += FragmentOffsetInBits;
+        break;
+      }
+      Ops.push_back(Op.getOp());
+      for (unsigned I = 0; I < Op.getNumArgs(); ++I)
+        Ops.push_back(Op.getArg(I));
+    }
+  }
+  Ops.push_back(dwarf::DW_OP_LLVM_fragment);
+  Ops.push_back(OffsetInBits);
+  Ops.push_back(SizeInBits);
+  return DIExpression::get(VMContext, Ops);
 }
 
 template <class... Ts>

Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=310014&r1=310013&r2=310014&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Thu Aug  3 18:19:54 2017
@@ -27,7 +27,9 @@
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/Instructions.h"
@@ -419,6 +421,23 @@ static bool GlobalUsersSafeToSRA(GlobalV
   return true;
 }
 
+/// Copy over the debug info for a variable to its SRA replacements.
+static void transferSRADebugInfo(GlobalVariable *GV, GlobalVariable *NGV,
+                                 uint64_t FragmentOffsetInBits,
+                                 uint64_t FragmentSizeInBits) {
+  DIBuilder DIB(*GV->getParent(), /*AllowUnresolved*/ false);
+  SmallVector<DIGlobalVariableExpression *, 1> GVs;
+  GV->getDebugInfo(GVs);
+  for (auto *GVE : GVs) {
+    DIVariable *Var = GVE->getVariable();
+    DIExpression *Expr = GVE->getExpression();
+    DIExpression *NExpr = DIB.createFragmentExpression(
+        FragmentOffsetInBits, FragmentSizeInBits, Expr);
+    auto *NGVE = DIGlobalVariableExpression::get(GVE->getContext(), Var, NExpr);
+    NGV->addDebugInfo(NGVE);
+  }
+}
+
 
 /// Perform scalar replacement of aggregates on the specified global variable.
 /// This opens the door for other optimizations by exposing the behavior of the
@@ -443,6 +462,7 @@ static GlobalVariable *SRAGlobal(GlobalV
     StartAlignment = DL.getABITypeAlignment(GV->getType());
 
   if (StructType *STy = dyn_cast<StructType>(Ty)) {
+    uint64_t FragmentOffset = 0;
     NewGlobals.reserve(STy->getNumElements());
     const StructLayout &Layout = *DL.getStructLayout(STy);
     for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
@@ -465,15 +485,22 @@ static GlobalVariable *SRAGlobal(GlobalV
       unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
       if (NewAlign > DL.getABITypeAlignment(STy->getElementType(i)))
         NGV->setAlignment(NewAlign);
+
+      // Copy over the debug info for the variable.
+      FragmentOffset = alignTo(FragmentOffset, NewAlign);
+      uint64_t Size = DL.getTypeSizeInBits(NGV->getValueType());
+      transferSRADebugInfo(GV, NGV, FragmentOffset, Size);
+      FragmentOffset += Size;
     }
   } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
     unsigned NumElements = STy->getNumElements();
     if (NumElements > 16 && GV->hasNUsesOrMore(16))
       return nullptr; // It's not worth it.
     NewGlobals.reserve(NumElements);
-
-    uint64_t EltSize = DL.getTypeAllocSize(STy->getElementType());
-    unsigned EltAlign = DL.getABITypeAlignment(STy->getElementType());
+    auto ElTy = STy->getElementType();
+    uint64_t EltSize = DL.getTypeAllocSize(ElTy);
+    unsigned EltAlign = DL.getABITypeAlignment(ElTy);
+    uint64_t FragmentSizeInBits = DL.getTypeSizeInBits(ElTy);
     for (unsigned i = 0, e = NumElements; i != e; ++i) {
       Constant *In = Init->getAggregateElement(i);
       assert(In && "Couldn't get element of initializer?");
@@ -494,6 +521,8 @@ static GlobalVariable *SRAGlobal(GlobalV
       unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
       if (NewAlign > EltAlign)
         NGV->setAlignment(NewAlign);
+
+      transferSRADebugInfo(GV, NGV, FragmentSizeInBits * i, FragmentSizeInBits);
     }
   }
 

Added: llvm/trunk/test/DebugInfo/Generic/global-sra-array.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/global-sra-array.ll?rev=310014&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/Generic/global-sra-array.ll (added)
+++ llvm/trunk/test/DebugInfo/Generic/global-sra-array.ll Thu Aug  3 18:19:54 2017
@@ -0,0 +1,129 @@
+; RUN: opt -S -globalopt < %s | FileCheck %s
+source_filename = "test.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.12.0"
+
+%struct.mystruct = type { i32, i64 }
+; Generated at -Os from:
+;
+; static struct { int a; char b; } array[2];
+; void __attribute__((nodebug)) foo(int in) { array[0].a = in; }
+; void __attribute__((nodebug)) bar(int in) { array[1].a = in; }
+; int main(int argc, char **argv)
+; {
+;   foo(argv[0][1]);
+;   bar(argv[0][1]);
+;   return array[0].a + array[1].a;
+; }
+
+%struct.anon = type { i32, i8 }
+
+; This array is first split into two struct, which are then split into their
+; elements, of which only .a survives.
+ at array = internal global [2 x %struct.anon] zeroinitializer, align 16, !dbg !0
+; CHECK: @array.0.0 = internal unnamed_addr global i32 0, align 16, !dbg ![[EL0:.*]]
+; CHECK: @array.1.0 = internal unnamed_addr global i32 0, align 8, !dbg ![[EL1:.*]]
+;
+; CHECK: ![[EL0]] = !DIGlobalVariableExpression(var: ![[VAR:.*]], expr: ![[EX1:.*]])
+; CHECK: ![[VAR]] = distinct !DIGlobalVariable(name: "array"
+; CHECK: ![[EX1]] = !DIExpression(DW_OP_LLVM_fragment, 0, 32)
+; CHECK: ![[EL1]] = !DIGlobalVariableExpression(var: ![[VAR]], expr: ![[EX2:.*]])
+; CHECK: ![[EX2]] = !DIExpression(DW_OP_LLVM_fragment, 64, 32)
+
+
+; Function Attrs: nounwind optsize ssp uwtable
+define void @foo(i32 %in) #0 {
+entry:
+  store i32 %in, i32* getelementptr inbounds ([2 x %struct.anon], [2 x %struct.anon]* @array, i64 0, i64 0, i32 0), align 16, !tbaa !20
+  ret void
+}
+
+; Function Attrs: nounwind optsize ssp uwtable
+define void @bar(i32 %in) #0 {
+entry:
+  store i32 %in, i32* getelementptr inbounds ([2 x %struct.anon], [2 x %struct.anon]* @array, i64 0, i64 1, i32 0), align 8, !tbaa !20
+  ret void
+}
+
+; Function Attrs: nounwind optsize ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) #0 !dbg !25 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %argc, metadata !31, metadata !33), !dbg !34
+  call void @llvm.dbg.value(metadata i8** %argv, metadata !32, metadata !33), !dbg !35
+  %0 = load i8*, i8** %argv, align 8, !dbg !36, !tbaa !37
+  %arrayidx1 = getelementptr inbounds i8, i8* %0, i64 1, !dbg !36
+  %1 = load i8, i8* %arrayidx1, align 1, !dbg !36, !tbaa !39
+  %conv = sext i8 %1 to i32, !dbg !36
+  call void @foo(i32 %conv) #2, !dbg !40
+  %2 = load i8*, i8** %argv, align 8, !dbg !41, !tbaa !37
+  %arrayidx3 = getelementptr inbounds i8, i8* %2, i64 1, !dbg !41
+  %3 = load i8, i8* %arrayidx3, align 1, !dbg !41, !tbaa !39
+  %conv4 = sext i8 %3 to i32, !dbg !41
+  call void @bar(i32 %conv4) #2, !dbg !42
+  %4 = load i32, i32* getelementptr inbounds ([2 x %struct.anon], [2 x %struct.anon]* @array, i64 0, i64 0, i32 0), align 16, !dbg !43, !tbaa !20
+  %5 = load i32, i32* getelementptr inbounds ([2 x %struct.anon], [2 x %struct.anon]* @array, i64 0, i64 1, i32 0), align 8, !dbg !44, !tbaa !20
+  %add = add nsw i32 %4, %5, !dbg !45
+  ret i32 %add, !dbg !46
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind optsize ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+attributes #2 = { optsize }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!15, !16, !17, !18}
+!llvm.ident = !{!19}
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "array", scope: !2, file: !3, line: 1, type: !6, isLocal: true, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 (trunk 309960) (llvm/trunk 309961)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "test.c", directory: "/")
+!4 = !{}
+!5 = !{!0}
+!6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 128, elements: !13)
+!7 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3, line: 1, size: 64, elements: !8)
+!8 = !{!9, !11}
+!9 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !7, file: !3, line: 1, baseType: !10, size: 32)
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !7, file: !3, line: 1, baseType: !12, size: 8, offset: 32)
+!12 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!13 = !{!14}
+!14 = !DISubrange(count: 2)
+!15 = !{i32 2, !"Dwarf Version", i32 4}
+!16 = !{i32 2, !"Debug Info Version", i32 3}
+!17 = !{i32 1, !"wchar_size", i32 4}
+!18 = !{i32 7, !"PIC Level", i32 2}
+!19 = !{!"clang version 6.0.0 (trunk 309960) (llvm/trunk 309961)"}
+!20 = !{!21, !22, i64 0}
+!21 = !{!"", !22, i64 0, !23, i64 4}
+!22 = !{!"int", !23, i64 0}
+!23 = !{!"omnipotent char", !24, i64 0}
+!24 = !{!"Simple C/C++ TBAA"}
+!25 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 4, type: !26, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !2, variables: !30)
+!26 = !DISubroutineType(types: !27)
+!27 = !{!10, !10, !28}
+!28 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !29, size: 64)
+!29 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 64)
+!30 = !{!31, !32}
+!31 = !DILocalVariable(name: "argc", arg: 1, scope: !25, file: !3, line: 4, type: !10)
+!32 = !DILocalVariable(name: "argv", arg: 2, scope: !25, file: !3, line: 4, type: !28)
+!33 = !DIExpression()
+!34 = !DILocation(line: 4, column: 14, scope: !25)
+!35 = !DILocation(line: 4, column: 27, scope: !25)
+!36 = !DILocation(line: 6, column: 7, scope: !25)
+!37 = !{!38, !38, i64 0}
+!38 = !{!"any pointer", !23, i64 0}
+!39 = !{!23, !23, i64 0}
+!40 = !DILocation(line: 6, column: 3, scope: !25)
+!41 = !DILocation(line: 7, column: 7, scope: !25)
+!42 = !DILocation(line: 7, column: 3, scope: !25)
+!43 = !DILocation(line: 8, column: 19, scope: !25)
+!44 = !DILocation(line: 8, column: 32, scope: !25)
+!45 = !DILocation(line: 8, column: 21, scope: !25)
+!46 = !DILocation(line: 8, column: 3, scope: !25)

Added: llvm/trunk/test/DebugInfo/Generic/global-sra-struct.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/global-sra-struct.ll?rev=310014&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/Generic/global-sra-struct.ll (added)
+++ llvm/trunk/test/DebugInfo/Generic/global-sra-struct.ll Thu Aug  3 18:19:54 2017
@@ -0,0 +1,132 @@
+; RUN: opt -S -globalopt < %s | FileCheck %s
+source_filename = "test.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.12.0"
+
+%struct.mystruct = type { i32, i64 }
+; Generated at -Os from:
+;
+; static struct mystruct {
+;     int a;
+;     long long int b;
+; } static_struct;
+; void __attribute__((nodebug)) foo(int in) { static_struct.a = in; }
+; void __attribute__((nodebug)) bar(int in) { static_struct.b = in; }
+; int main(int argc, char **argv)
+; {
+;     foo(argv[0][1]);
+;     bar(argv[0][1]);
+;     return static_struct.a + static_struct.b;
+; }
+
+; CHECK: @static_struct.0 = internal unnamed_addr global i32 0, align 8, !dbg ![[EL0:.*]]
+; CHECK: @static_struct.1 = internal unnamed_addr global i64 0, align 8, !dbg ![[EL1:.*]]
+
+; CHECK: ![[EL0]] = !DIGlobalVariableExpression(var: ![[VAR:.*]], expr: ![[EX1:.*]])
+; CHECK: ![[VAR]] = distinct !DIGlobalVariable(name: "static_struct"
+; CHECK: ![[EX1]] = !DIExpression(DW_OP_LLVM_fragment, 0, 32)
+; CHECK: ![[EL1]] = !DIGlobalVariableExpression(var: ![[VAR]], expr: ![[EX2:.*]])
+; CHECK: ![[EX2]] = !DIExpression(DW_OP_LLVM_fragment, 32, 64)
+
+ at static_struct = internal global %struct.mystruct zeroinitializer, align 8, !dbg !0
+
+; Function Attrs: nounwind optsize ssp uwtable
+define void @foo(i32 %in) #0 {
+entry:
+  store i32 %in, i32* getelementptr inbounds (%struct.mystruct, %struct.mystruct* @static_struct, i32 0, i32 0), align 8, !tbaa !17
+  ret void
+}
+
+; Function Attrs: nounwind optsize ssp uwtable
+define void @bar(i32 %in) #0 {
+entry:
+  %conv = sext i32 %in to i64
+  store i64 %conv, i64* getelementptr inbounds (%struct.mystruct, %struct.mystruct* @static_struct, i32 0, i32 1), align 8, !tbaa !23
+  ret void
+}
+
+; Function Attrs: nounwind optsize ssp uwtable
+define i32 @main(i32 %argc, i8** %argv) #0 !dbg !24 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %argc, metadata !31, metadata !33), !dbg !34
+  call void @llvm.dbg.value(metadata i8** %argv, metadata !32, metadata !33), !dbg !35
+  %0 = load i8*, i8** %argv, align 8, !dbg !36, !tbaa !37
+  %arrayidx1 = getelementptr inbounds i8, i8* %0, i64 1, !dbg !36
+  %1 = load i8, i8* %arrayidx1, align 1, !dbg !36, !tbaa !39
+  %conv = sext i8 %1 to i32, !dbg !36
+  call void @foo(i32 %conv) #2, !dbg !40
+  %2 = load i8*, i8** %argv, align 8, !dbg !41, !tbaa !37
+  %arrayidx3 = getelementptr inbounds i8, i8* %2, i64 1, !dbg !41
+  %3 = load i8, i8* %arrayidx3, align 1, !dbg !41, !tbaa !39
+  %conv4 = sext i8 %3 to i32, !dbg !41
+  call void @bar(i32 %conv4) #2, !dbg !42
+  %4 = load i32, i32* getelementptr inbounds (%struct.mystruct, %struct.mystruct* @static_struct, i32 0, i32 0), align 8, !dbg !43, !tbaa !17
+  %conv5 = sext i32 %4 to i64, !dbg !44
+  %5 = load i64, i64* getelementptr inbounds (%struct.mystruct, %struct.mystruct* @static_struct, i32 0, i32 1), align 8, !dbg !45, !tbaa !23
+  %add = add nsw i64 %conv5, %5, !dbg !46
+  %conv6 = trunc i64 %add to i32, !dbg !44
+  ret i32 %conv6, !dbg !47
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind optsize ssp uwtable }
+attributes #1 = { nounwind readnone speculatable }
+attributes #2 = { optsize }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!12, !13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "static_struct", scope: !2, file: !3, line: 4, type: !6, isLocal: true, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 (trunk 309852) (llvm/trunk 309850)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "test.c", directory: "/")
+!4 = !{}
+!5 = !{!0}
+!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "mystruct", file: !3, line: 1, size: 128, elements: !7)
+!7 = !{!8, !10}
+!8 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !6, file: !3, line: 2, baseType: !9, size: 32)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !6, file: !3, line: 3, baseType: !11, size: 64, offset: 64)
+!11 = !DIBasicType(name: "long long int", size: 64, encoding: DW_ATE_signed)
+!12 = !{i32 2, !"Dwarf Version", i32 4}
+!13 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{i32 1, !"wchar_size", i32 4}
+!15 = !{i32 7, !"PIC Level", i32 2}
+!16 = !{!"clang version 6.0.0 (trunk 309852) (llvm/trunk 309850)"}
+!17 = !{!18, !19, i64 0}
+!18 = !{!"mystruct", !19, i64 0, !22, i64 8}
+!19 = !{!"int", !20, i64 0}
+!20 = !{!"omnipotent char", !21, i64 0}
+!21 = !{!"Simple C/C++ TBAA"}
+!22 = !{!"long long", !20, i64 0}
+!23 = !{!18, !22, i64 8}
+!24 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 7, type: !25, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: true, unit: !2, variables: !30)
+!25 = !DISubroutineType(types: !26)
+!26 = !{!9, !9, !27}
+!27 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !28, size: 64)
+!28 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !29, size: 64)
+!29 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!30 = !{!31, !32}
+!31 = !DILocalVariable(name: "argc", arg: 1, scope: !24, file: !3, line: 7, type: !9)
+!32 = !DILocalVariable(name: "argv", arg: 2, scope: !24, file: !3, line: 7, type: !27)
+!33 = !DIExpression()
+!34 = !DILocation(line: 7, column: 14, scope: !24)
+!35 = !DILocation(line: 7, column: 27, scope: !24)
+!36 = !DILocation(line: 9, column: 9, scope: !24)
+!37 = !{!38, !38, i64 0}
+!38 = !{!"any pointer", !20, i64 0}
+!39 = !{!20, !20, i64 0}
+!40 = !DILocation(line: 9, column: 5, scope: !24)
+!41 = !DILocation(line: 10, column: 9, scope: !24)
+!42 = !DILocation(line: 10, column: 5, scope: !24)
+!43 = !DILocation(line: 11, column: 26, scope: !24)
+!44 = !DILocation(line: 11, column: 12, scope: !24)
+!45 = !DILocation(line: 11, column: 44, scope: !24)
+!46 = !DILocation(line: 11, column: 28, scope: !24)
+!47 = !DILocation(line: 11, column: 5, scope: !24)




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