SROA: Defer migrating the debug info for new allocas until after all partitions are created.

[aprantl]

Summary

SROA: Defer migrating the debug info for new allocas until after all partitions are created.
As discussed on #llvm today.

[chandlerc]

lib/Transforms/Scalar/SROA.cpp

3594

Rather than a member, how about a local here...

3608–3612

And change rewritePartition so that if it makes changes it returns the changed alloca. We can compare against &AI to handle the case that we got back the same alloca that went in, and we'll never get back the same alloca when we end up with more than one.

[chandlerc]

Is it possible to craft a test case for this? I'm thinking an alloca which needs rewriting but not splitting...

lib/Transforms/Scalar/SROA.cpp

3601

Just call the parameters the same name as the members. This does the right thing in the initializer list. I would probably use AI, Offset, and Size.

3604

I think you at least want a smallvector with 1 piece in it.

3612–3613

Any reason not to actually handle the null case for now? I think the code would be pretty clean:

if (AllocaInst *NewAI = rewritePartition(AI, AS, P)) {
  Changed = true;
  if (NewAI != &AI)
    Pieces.push_back(...);
}
++NumPartitions;

3627

I would say:

bool IsSplit = ...;

[aprantl]

• Addressed all of Chandler's comments.
• Added a testcase were the alloca is rewritten but not repartitioned.

[aprantl]

Tiny update: Don't add the dbg.declare to DeadInsts. It's redundant because it will get removed automatically when the alloca is removed. It's also a bad idea to remove the same instruction more than once.

[aprantl]

When compiling really large programs the pointer values in the DbgDeclares map may actually get recycled.

• clear the pointer map when entering a function
• remove values after the dbg.declare has been deleted

tested via an assertion.

[chandlerc]

Just want to say this LGTM in whatever form you decide to commit it.

I know there was a revert in between, so feel free to just commit the new version, or re-apply the old one and then commit this on top. Whatever works.

[aprantl]

This was r226598.

lib/Transforms/Scalar/SROA.cpp

class SROA : public FunctionPass {
   /// \brief A worklist of select instructions to speculate prior to promoting
   /// allocas.
   ///
   /// All of these select instructions have been checked for the safety of
   /// speculation and by being speculated will allow promoting allocas
   /// currently in the promotable queue.
   SetVector<SelectInst *, SmallVector<SelectInst *, 2>> SpeculatableSelects;
 
+  /// Debug intrinsics do not show up as regular uses in the
+  /// IR. This side-table holds the missing use edges.
+  DenseMap<AllocaInst *, DbgDeclareInst *> DbgDeclares;
+
 public:
   SROA(bool RequiresDomTree = true)
       : FunctionPass(ID), RequiresDomTree(RequiresDomTree), C(nullptr),
         DL(nullptr), DT(nullptr) {
     initializeSROAPass(*PassRegistry::getPassRegistry());
   }
   bool runOnFunction(Function &F) override;
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
   const char *getPassName() const override { return "SROA"; }
   static char ID;
 
 private:
   friend class PHIOrSelectSpeculator;
   friend class AllocaSliceRewriter;
 
-  bool rewritePartition(AllocaInst &AI, AllocaSlices &AS,
+  AllocaInst *rewritePartition(AllocaInst &AI, AllocaSlices &AS,
                                AllocaSlices::Partition &P);
   bool splitAlloca(AllocaInst &AI, AllocaSlices &AS);
   bool runOnAlloca(AllocaInst &AI);
   void clobberUse(Use &U);
   void deleteDeadInstructions(SmallPtrSetImpl<AllocaInst *> &DeletedAllocas);
   bool promoteAllocas(Function &F);
 };
 }
 

 /// This routine drives both of the rewriting goals of the SROA pass. It tries
 /// to rewrite uses of an alloca partition to be conducive for SSA value
 /// promotion. If the partition needs a new, more refined alloca, this will
 /// build that new alloca, preserving as much type information as possible, and
 /// rewrite the uses of the old alloca to point at the new one and have the
 /// appropriate new offsets. It also evaluates how successful the rewrite was
 /// at enabling promotion and if it was successful queues the alloca to be
 /// promoted.
-bool SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
+AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
                                    AllocaSlices::Partition &P) {
   // Try to compute a friendly type for this partition of the alloca. This
   // won't always succeed, in which case we fall back to a legal integer type
   // or an i8 array of an appropriate size.
   Type *SliceTy = nullptr;
   if (Type *CommonUseTy = findCommonType(P.begin(), P.end(), P.endOffset()))
     if (DL->getTypeAllocSize(CommonUseTy) >= P.size())
       SliceTy = CommonUseTy;
   if (!SliceTy)
AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
   // perform phi and select speculation.
   AllocaInst *NewAI;
   if (SliceTy == AI.getAllocatedType()) {
     assert(P.beginOffset() == 0 &&
            "Non-zero begin offset but same alloca type");
     NewAI = &AI;
     // FIXME: We should be able to bail at this point with "nothing changed".
     // FIXME: We might want to defer PHI speculation until after here.
+    // FIXME: return nullptr;
   } else {
     unsigned Alignment = AI.getAlignment();
     if (!Alignment) {
       // The minimum alignment which users can rely on when the explicit
       // alignment is omitted or zero is that required by the ABI for this
       // type.
       Alignment = DL->getABITypeAlignment(AI.getAllocatedType());
     }
if (Promotable) {
     if (NewAI != &AI)
       Worklist.insert(NewAI);
 
     // Drop any post-promotion work items if promotion didn't happen.
     while (PostPromotionWorklist.size() > PPWOldSize)
       PostPromotionWorklist.pop_back();
   }
 
-  return true;
+  return NewAI;
 }
 
 /// \brief Walks the slices of an alloca and form partitions based on them,
 /// rewriting each of their uses.
 bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
   if (AS.begin() == AS.end())
     return false;
 
   unsigned NumPartitions = 0;
   bool Changed = false;
 
+  /// \brief Describes the allocas introduced by rewritePartition
+  /// in order to migrate the debug info.
+  struct Piece {
+    AllocaInst *Alloca;
+    uint64_t Offset;
+    uint64_t Size;
+    Piece(AllocaInst *AI, uint64_t O, uint64_t S)
+      : Alloca(AI), Offset(O), Size(S) {}
+  };
+  SmallVector<Piece, 4> Pieces;
+
   // Rewrite each parttion.
   for (auto &P : AS.partitions()) {
-    Changed |= rewritePartition(AI, AS, P);
+    if (AllocaInst *NewAI = rewritePartition(AI, AS, P)) {
+      Changed = true;
+      if (NewAI != &AI)
+        Pieces.push_back(Piece(NewAI, P.beginOffset(), P.size()));
+    }
     ++NumPartitions;
   }
 
   NumAllocaPartitions += NumPartitions;
   MaxPartitionsPerAlloca =
       std::max<unsigned>(NumPartitions, MaxPartitionsPerAlloca);
 
+  // Migrate debug information from the old alloca to the new alloca(s)
+  // and the individial partitions.
+  if (DbgDeclareInst *DbgDecl = DbgDeclares.lookup(&AI)) {
+    DIVariable Var(DbgDecl->getVariable());
+    DIExpression Expr(DbgDecl->getExpression());
+    DIBuilder DIB(*AI.getParent()->getParent()->getParent(),
+                  /*AllowUnresolved*/ false);
+    bool IsSplit = Pieces.size() > 1;
+    for (auto Piece : Pieces) {
+      // Create a piece expression describing the new partition or reuse AI's
+      // expression if there is only one partition.
+      if (IsSplit)
+        Expr = DIB.createPieceExpression(Piece.Offset, Piece.Size);
+      Instruction *NewDDI = DIB.insertDeclare(Piece.Alloca, Var, Expr, &AI);
+      NewDDI->setDebugLoc(DbgDecl->getDebugLoc());
+      assert(!DbgDeclares.count(Piece.Alloca) && "alloca already described");
+      DbgDeclares.insert(std::make_pair(Piece.Alloca,
+                                        cast<DbgDeclareInst>(NewDDI)));
+    }
+  }
   return Changed;
 }
 
 /// \brief Clobber a use with undef, deleting the used value if it becomes dead.
 void SROA::clobberUse(Use &U) {
   Value *OldV = U;
   // Replace the use with an undef value.
   U = UndefValue::get(OldV->getType());
while (!DeadInsts.empty()) {
     for (Use &Operand : I->operands())
       if (Instruction *U = dyn_cast<Instruction>(Operand)) {
         // Zero out the operand and see if it becomes trivially dead.
         Operand = nullptr;
         if (isInstructionTriviallyDead(U))
           DeadInsts.insert(U);
       }
 
-    if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
+    if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
       DeletedAllocas.insert(AI);
+      if (DbgDeclareInst *DbgDecl = DbgDeclares.lookup(AI)) {
+        DbgDecl->eraseFromParent();
+        DbgDeclares.erase(AI);
+      }
+    }
 
     ++NumDeleted;
     I->eraseFromParent();
   }
 }
 
 static void enqueueUsersInWorklist(Instruction &I,
                                    SmallVectorImpl<Instruction *> &Worklist,
if (!DLP) {
     return false;
   }
   DL = &DLP->getDataLayout();
   DominatorTreeWrapperPass *DTWP =
       getAnalysisIfAvailable<DominatorTreeWrapperPass>();
   DT = DTWP ? &DTWP->getDomTree() : nullptr;
   AT = &getAnalysis<AssumptionTracker>();
 
+  DbgDeclares.clear();
   BasicBlock &EntryBB = F.getEntryBlock();
   for (BasicBlock::iterator I = EntryBB.begin(), E = std::prev(EntryBB.end());
-       I != E; ++I)
+       I != E; ++I) {
     if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
       Worklist.insert(AI);
+    else if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I))
+      if (auto AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress()))
+        DbgDeclares.insert(std::make_pair(AI, DDI));
+  }
 
   bool Changed = false;
   // A set of deleted alloca instruction pointers which should be removed from
   // the list of promotable allocas.
   SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
 
   do {
     while (!Worklist.empty()) {

test/DebugInfo/X86/array2.ll

 ; ModuleID = 'array.c'
 ;
 ; From (clang -g -c -O0):
 ;
 ; void f(int* p) {
 ;   p[0] = 42;
 ; }
 ;
 ; int main(int argc, char** argv) {
 ;   int array[4] = { 0, 1, 2, 3 };
 ;   f(array);
 ;   return array[0];
 ; }
 ;
 ; RUN: opt %s -O2 -S -o - | FileCheck %s
-; Test that we do not lower dbg.declares for arrays.
+; Test that we correctly lower dbg.declares for arrays.
 ;
 ; CHECK: define i32 @main
-; CHECK: call void @llvm.dbg.value
-; CHECK: call void @llvm.dbg.value
-; CHECK: call void @llvm.dbg.declare
+; CHECK: call void @llvm.dbg.value(metadata i32 42, i64 0, metadata ![[ARRAY:[0-9]+]], metadata ![[EXPR:[0-9]+]])
+; CHECK: ![[ARRAY]] = {{.*}}; [ DW_TAG_auto_variable ] [array] [line 6]
+; CHECK: ![[EXPR]] = {{.*}}; [ DW_TAG_expression ] [DW_OP_piece offset=0, size=4]
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.9.0"
 
 @main.array = private unnamed_addr constant [4 x i32] [i32 0, i32 1, i32 2, i32 3], align 16
 
 ; Function Attrs: nounwind ssp uwtable
 define void @f(i32* %p) #0 {
 entry:

test/DebugInfo/X86/sroasplit-1.ll

+; RUN: opt %s -sroa -verify -S -o - | FileCheck %s
+;
+; Test that we can partial emit debug info for aggregates repeatedly
+; split up by SROA.
+;
+;    // Compile with -O1
+;    typedef struct {
+;      int a;
+;      long int b;
+;    } Inner;
+;
+;    typedef struct {
+;      Inner inner[2];
+;    } Outer;
+;
+;    int foo(Outer outer) {
+;      Inner i1 = outer.inner[1];
+;      return i1.a;
+;    }
+;
+
+; Verify that SROA creates a variable piece when splitting i1.
+; CHECK: %[[I1:.*]] = alloca [12 x i8], align 4
+; CHECK: call void @llvm.dbg.declare(metadata [12 x i8]* %[[I1]], metadata ![[VAR:[0-9]+]], metadata ![[PIECE1:[0-9]+]])
+; CHECK: call void @llvm.dbg.value(metadata i32 %[[A:.*]], i64 0, metadata ![[VAR]], metadata ![[PIECE2:[0-9]+]])
+; CHECK: ret i32 %[[A]]
+; Read Var and Piece:
+; CHECK: ![[VAR]] = {{.*}} ; [ DW_TAG_auto_variable ] [i1] [line 11]
+; CHECK: ![[PIECE1]] = {{.*}} ; [ DW_TAG_expression ] [DW_OP_piece offset=4, size=12]
+; CHECK: ![[PIECE2]] = {{.*}} ; [ DW_TAG_expression ] [DW_OP_piece offset=0, size=4]
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+%struct.Outer = type { [2 x %struct.Inner] }
+%struct.Inner = type { i32, i64 }
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @foo(%struct.Outer* byval align 8 %outer) #0 {
+entry:
+  %i1 = alloca %struct.Inner, align 8
+  call void @llvm.dbg.declare(metadata %struct.Outer* %outer, metadata !25, metadata !2), !dbg !26
+  call void @llvm.dbg.declare(metadata %struct.Inner* %i1, metadata !27, metadata !2), !dbg !28
+  %inner = getelementptr inbounds %struct.Outer* %outer, i32 0, i32 0, !dbg !28
+  %arrayidx = getelementptr inbounds [2 x %struct.Inner]* %inner, i32 0, i64 1, !dbg !28
+  %0 = bitcast %struct.Inner* %i1 to i8*, !dbg !28
+  %1 = bitcast %struct.Inner* %arrayidx to i8*, !dbg !28
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %0, i8* %1, i64 16, i32 8, i1 false), !dbg !28
+  %a = getelementptr inbounds %struct.Inner* %i1, i32 0, i32 0, !dbg !29
+  %2 = load i32* %a, align 4, !dbg !29
+  ret i32 %2, !dbg !29
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) #2
+
+attributes #0 = { nounwind ssp uwtable }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!22, !23}
+!llvm.ident = !{!24}
+
+!0 = !{!"0x11\0012\00clang version 3.5.0 \000\00\000\00\001", !1, !2, !2, !3, !2, !2} ; [ DW_TAG_compile_unit ] [ DW_TAG_compile_unit ] [sroasplit-1.c] [DW_LANG_C99]
+!1 = !{!"sroasplit-1.c", !""}
+!2 = !{}
+!3 = !{!4}
+!4 = !{!"0x2e\00foo\00foo\00\0010\000\001\000\006\00256\000\0010", !1, !5, !6, null, i32 (%struct.Outer*)* @foo, null, null, !2} ; [ DW_TAG_subprogram ] [ DW_TAG_subprogram ] [line 10] [def] [foo]
+!5 = !{!"0x29", !1} ; [ DW_TAG_file_type ] [ DW_TAG_file_type ] [sroasplit-1.c]
+!6 = !{!"0x15\00\000\000\000\000\000\000", i32 0, null, null, !7, null, null, null} ; [ DW_TAG_subroutine_type ] [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = !{!8, !9}
+!8 = !{!"0x24\00int\000\0032\0032\000\000\005", null, null} ; [ DW_TAG_base_type ] [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = !{!"0x16\00Outer\008\000\000\000\000", !1, null, !10} ; [ DW_TAG_typedef ] [ DW_TAG_typedef ] [Outer] [line 8, size 0, align 0, offset 0] [from ]
+!10 = !{!"0x13\00\006\00256\0064\000\000\000", !1, null, null, !11, null, null, null} ; [ DW_TAG_structure_type ] [line 6, size 256, align 64, offset 0] [def] [from ]
+!11 = !{!12}
+!12 = !{!"0xd\00inner\007\00256\0064\000\000", !1, !10, !13} ; [ DW_TAG_member ] [inner] [line 7, size 256, align 64, offset 0] [from ]
+!13 = !{!"0x1\00\000\00256\0064\000\000", null, null, !14, !20, i32 0, null, null, null} ; [ DW_TAG_array_type ] [line 0, size 256, align 64, offset 0] [from Inner]
+!14 = !{!"0x16\00Inner\004\000\000\000\000", !1, null, !15} ; [ DW_TAG_typedef ] [ DW_TAG_typedef ] [Inner] [line 4, size 0, align 0, offset 0] [from ]
+!15 = !{!"0x13\00\001\00128\0064\000\000\000", !1, null, null, !16, null, null, null} ; [ DW_TAG_structure_type ] [line 1, size 128, align 64, offset 0] [def] [from ]
+!16 = !{!17, !18}
+!17 = !{!"0xd\00a\002\0032\0032\000\000", !1, !15, !8} ; [ DW_TAG_member ] [a] [line 2, size 32, align 32, offset 0] [from int]
+!18 = !{!"0xd\00b\003\0064\0064\0064\000", !1, !15, !19} ; [ DW_TAG_member ] [b] [line 3, size 64, align 64, offset 64] [from long int]
+!19 = !{!"0x24\00long int\000\0064\0064\000\000\005", null, null} ; [ DW_TAG_base_type ] [ DW_TAG_base_type ] [long int] [line 0, size 64, align 64, offset 0, enc DW_ATE_signed]
+!20 = !{!21}
+!21 = !{!"0x21\000\002"}        ; [ DW_TAG_subrange_type ] [0, 1]
+!22 = !{i32 2, !"Dwarf Version", i32 2}
+!23 = !{i32 1, !"Debug Info Version", i32 2}
+!24 = !{!"clang version 3.5.0 "}
+!25 = !{!"0x101\00outer\0016777226\000", !4, !5, !9} ; [ DW_TAG_arg_variable ] [ DW_TAG_arg_variable ] [outer] [line 10]
+!26 = !{i32 10, i32 0, !4, null}
+!27 = !{!"0x100\00i1\0011\000", !4, !5, !14} ; [ DW_TAG_auto_variable ] [ DW_TAG_auto_variable ] [i1] [line 11]
+!28 = !{i32 11, i32 0, !4, null}
+!29 = !{i32 12, i32 0, !4, null}

test/DebugInfo/X86/sroasplit-2.ll

+; RUN: opt %s -sroa -verify -S -o - | FileCheck %s
+;
+; Test that we can partial emit debug info for aggregates repeatedly
+; split up by SROA.
+;
+;    // Compile with -O1
+;    typedef struct {
+;      int a;
+;      int b;
+;    } Inner;
+;
+;    typedef struct {
+;      Inner inner[2];
+;    } Outer;
+;
+;    int foo(Outer outer) {
+;      Inner i1 = outer.inner[1];
+;      return i1.a;
+;    }
+;
+
+; Verify that SROA creates a variable piece when splitting i1.
+; CHECK:  call void @llvm.dbg.value(metadata i64 %outer.coerce0, i64 0, metadata ![[O:[0-9]+]], metadata ![[PIECE1:[0-9]+]]),
+; CHECK:  call void @llvm.dbg.value(metadata i64 %outer.coerce1, i64 0, metadata ![[O]], metadata ![[PIECE2:[0-9]+]]),
+; CHECK:  call void @llvm.dbg.value({{.*}}, i64 0, metadata ![[I1:[0-9]+]], metadata ![[PIECE3:[0-9]+]]),
+; CHECK-DAG: ![[O]] = {{.*}} [ DW_TAG_arg_variable ] [outer] [line 10]
+; CHECK-DAG: ![[PIECE1]] = {{.*}} [ DW_TAG_expression ] [DW_OP_piece offset=0, size=8]
+; CHECK-DAG: ![[PIECE2]] = {{.*}} [ DW_TAG_expression ] [DW_OP_piece offset=8, size=8]
+; CHECK-DAG: ![[I1]] = {{.*}} [ DW_TAG_auto_variable ] [i1] [line 11]
+; CHECK-DAG: ![[PIECE3]] = {{.*}} [ DW_TAG_expression ] [DW_OP_piece offset=0, size=4]
+
+; ModuleID = 'sroasplit-2.c'
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+%struct.Outer = type { [2 x %struct.Inner] }
+%struct.Inner = type { i32, i32 }
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @foo(i64 %outer.coerce0, i64 %outer.coerce1) #0 {
+  %outer = alloca %struct.Outer, align 8
+  %i1 = alloca %struct.Inner, align 4
+  %1 = bitcast %struct.Outer* %outer to { i64, i64 }*
+  %2 = getelementptr { i64, i64 }* %1, i32 0, i32 0
+  store i64 %outer.coerce0, i64* %2
+  %3 = getelementptr { i64, i64 }* %1, i32 0, i32 1
+  store i64 %outer.coerce1, i64* %3
+  call void @llvm.dbg.declare(metadata %struct.Outer* %outer, metadata !24, metadata !2), !dbg !25
+  call void @llvm.dbg.declare(metadata %struct.Inner* %i1, metadata !26, metadata !2), !dbg !27
+  %4 = getelementptr inbounds %struct.Outer* %outer, i32 0, i32 0, !dbg !27
+  %5 = getelementptr inbounds [2 x %struct.Inner]* %4, i32 0, i64 1, !dbg !27
+  %6 = bitcast %struct.Inner* %i1 to i8*, !dbg !27
+  %7 = bitcast %struct.Inner* %5 to i8*, !dbg !27
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %6, i8* %7, i64 8, i32 4, i1 false), !dbg !27
+  %8 = getelementptr inbounds %struct.Inner* %i1, i32 0, i32 0, !dbg !28
+  %9 = load i32* %8, align 4, !dbg !28
+  ret i32 %9, !dbg !28
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) #2
+
+attributes #0 = { nounwind ssp uwtable "no-frame-pointer-elim"="true" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!21, !22}
+!llvm.ident = !{!23}
+
+!0 = !{!"0x11\0012\00clang version 3.5.0 \000\00\000\00\001", !1, !2, !2, !3, !2, !2} ; [ DW_TAG_compile_unit ] [ DW_TAG_compile_unit ] [sroasplit-2.c] [DW_LANG_C99]
+!1 = !{!"sroasplit-2.c", !""}
+!2 = !{}
+!3 = !{!4}
+!4 = !{!"0x2e\00foo\00foo\00\0010\000\001\000\006\00256\000\0010", !1, !5, !6, null, i32 (i64, i64)* @foo, null, null, !2} ; [ DW_TAG_subprogram ] [ DW_TAG_subprogram ] [line 10] [def] [foo]
+!5 = !{!"0x29", !1} ; [ DW_TAG_file_type ] [ DW_TAG_file_type ] [sroasplit-2.c]
+!6 = !{!"0x15\00\000\000\000\000\000\000", i32 0, null, null, !7, null, null, null} ; [ DW_TAG_subroutine_type ] [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = !{!8, !9}
+!8 = !{!"0x24\00int\000\0032\0032\000\000\005", null, null} ; [ DW_TAG_base_type ] [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = !{!"0x16\00Outer\008\000\000\000\000", !1, null, !10} ; [ DW_TAG_typedef ] [ DW_TAG_typedef ] [Outer] [line 8, size 0, align 0, offset 0] [from ]
+!10 = !{!"0x13\00\006\00128\0032\000\000\000", !1, null, null, !11, null, null, null} ; [ DW_TAG_structure_type ] [line 6, size 128, align 32, offset 0] [def] [from ]
+!11 = !{!12}
+!12 = !{!"0xd\00inner\007\00128\0032\000\000", !1, !10, !13} ; [ DW_TAG_member ] [inner] [line 7, size 128, align 32, offset 0] [from ]
+!13 = !{!"0x1\00\000\00128\0032\000\000", null, null, !14, !19, i32 0, null, null, null} ; [ DW_TAG_array_type ] [line 0, size 128, align 32, offset 0] [from Inner]
+!14 = !{!"0x16\00Inner\004\000\000\000\000", !1, null, !15} ; [ DW_TAG_typedef ] [ DW_TAG_typedef ] [Inner] [line 4, size 0, align 0, offset 0] [from ]
+!15 = !{!"0x13\00\001\0064\0032\000\000\000", !1, null, null, !16, null, null, null} ; [ DW_TAG_structure_type ] [line 1, size 64, align 32, offset 0] [def] [from ]
+!16 = !{!17, !18}
+!17 = !{!"0xd\00a\002\0032\0032\000\000", !1, !15, !8} ; [ DW_TAG_member ] [a] [line 2, size 32, align 32, offset 0] [from int]
+!18 = !{!"0xd\00b\003\0032\0032\0032\000", !1, !15, !8} ; [ DW_TAG_member ] [b] [line 3, size 32, align 32, offset 32] [from int]
+!19 = !{!20}
+!20 = !{!"0x21\000\002"}        ; [ DW_TAG_subrange_type ] [0, 1]
+!21 = !{i32 2, !"Dwarf Version", i32 2}
+!22 = !{i32 1, !"Debug Info Version", i32 2}
+!23 = !{!"clang version 3.5.0 "}
+!24 = !{!"0x101\00outer\0016777226\000", !4, !5, !9} ; [ DW_TAG_arg_variable ] [ DW_TAG_arg_variable ] [outer] [line 10]
+!25 = !{i32 10, i32 0, !4, null}
+!26 = !{!"0x100\00i1\0011\000", !4, !5, !14} ; [ DW_TAG_auto_variable ] [ DW_TAG_auto_variable ] [i1] [line 11]
+!27 = !{i32 11, i32 0, !4, null}
+!28 = !{i32 12, i32 0, !4, null}

test/DebugInfo/X86/sroasplit-3.ll

+; RUN: opt %s -sroa -verify -S -o - | FileCheck %s
+; ModuleID = 'test.c'
+; Test that SROA updates the debug info correctly if an alloca was rewritten but
+; not partitioned into multiple allocas.
+;
+; CHECK: call void @llvm.dbg.value(metadata float %s.coerce, i64 0, metadata ![[VAR:[0-9]+]], metadata ![[EXPR:[0-9]+]])
+; CHECK: ![[VAR]] = {{.*}} [ DW_TAG_arg_variable ] [s] [line 3]
+; CHECK: ![[EXPR]] = {{.*}} [ DW_TAG_expression ]
+; CHECK-NOT: DW_OP_piece
+
+;
+; struct S { float f; };
+;  
+; float foo(struct S s) {
+;   return s.f;
+; }
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.10.0"
+
+%struct.S = type { float }
+
+; Function Attrs: nounwind ssp uwtable
+define float @foo(float %s.coerce) #0 {
+entry:
+  %s = alloca %struct.S, align 4
+  %coerce.dive = getelementptr %struct.S* %s, i32 0, i32 0
+  store float %s.coerce, float* %coerce.dive, align 1
+  call void @llvm.dbg.declare(metadata %struct.S* %s, metadata !16, metadata !17), !dbg !18
+  %f = getelementptr inbounds %struct.S* %s, i32 0, i32 0, !dbg !19
+  %0 = load float* %f, align 4, !dbg !19
+  ret float %0, !dbg !19
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind ssp uwtable }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!12, !13, !14}
+!llvm.ident = !{!15}
+
+!0 = !{!"0x11\0012\00clang version 3.6.0 \000\00\000\00\001", !1, !2, !2, !3, !2, !2} ; [ DW_TAG_compile_unit ] [/Volumes/Data/llvm/_build.ninja.debug/test.c] [DW_LANG_C99]
+!1 = !{!"test.c", !"/Volumes/Data/llvm/_build.ninja.debug"}
+!2 = !{}
+!3 = !{!4}
+!4 = !{!"0x2e\00foo\00foo\00\003\000\001\000\000\00256\000\003", !1, !5, !6, null, float (float)* @foo, null, null, !2} ; [ DW_TAG_subprogram ] [line 3] [def] [foo]
+!5 = !{!"0x29", !1}                               ; [ DW_TAG_file_type ] [/Volumes/Data/llvm/_build.ninja.debug/test.c]
+!6 = !{!"0x15\00\000\000\000\000\000\000", null, null, null, !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = !{!8, !9}
+!8 = !{!"0x24\00float\000\0032\0032\000\000\004", null, null} ; [ DW_TAG_base_type ] [float] [line 0, size 32, align 32, offset 0, enc DW_ATE_float]
+!9 = !{!"0x13\00S\001\0032\0032\000\000\000", !1, null, null, !10, null, null, null} ; [ DW_TAG_structure_type ] [S] [line 1, size 32, align 32, offset 0] [def] [from ]
+!10 = !{!11}
+!11 = !{!"0xd\00f\001\0032\0032\000\000", !1, !9, !8} ; [ DW_TAG_member ] [f] [line 1, size 32, align 32, offset 0] [from float]
+!12 = !{i32 2, !"Dwarf Version", i32 2}
+!13 = !{i32 2, !"Debug Info Version", i32 2}
+!14 = !{i32 1, !"PIC Level", i32 2}
+!15 = !{!"clang version 3.6.0 "}
+!16 = !{!"0x101\00s\0016777219\000", !4, !5, !9}  ; [ DW_TAG_arg_variable ] [s] [line 3]
+!17 = !{!"0x102"}                                 ; [ DW_TAG_expression ]
+!18 = !{i32 3, i32 20, !4, null}
+!19 = !{i32 4, i32 2, !4, null}