Try to not lose variable's debug info during instcombine.

This is done by lowering dbg.declare intrinsic into dbg.value intrinsic.
Radar 9143931.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127834 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 92 insertions, 0 deletions

diff --git a/include/llvm/Transforms/Utils/Local.h b/include/llvm/Transforms/Utils/Local.h
index 8f97428649..16bcc54503 100644
--- a/include/llvm/Transforms/Utils/Local.h
+++ b/include/llvm/Transforms/Utils/Local.h
@@ -19,6 +19,7 @@ namespace llvm {
 
 class User;
 class BasicBlock;
+class Function;
 class BranchInst;
 class Instruction;
 class DbgDeclareInst;
@@ -169,6 +170,10 @@ static inline unsigned getKnownAlignment(Value *V, const TargetData *TD = 0) {
 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
                                      StoreInst *SI, DIBuilder &Builder);
 
+/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
+/// of llvm.dbg.value intrinsics.
+bool LowerDbgDeclare(Function &F);
+
 } // End llvm namespace
 
 #endif
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 37123d0621..d88162a703 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1648,6 +1648,10 @@ bool InstCombiner::runOnFunction(Function &F) {
   
   bool EverMadeChange = false;
 
+  // Lower dbg.declare intrinsics otherwise their value may be clobbered
+  // by instcombiner.
+  EverMadeChange = LowerDbgDeclare(F);
+
   // Iterate while there is work to do.
   unsigned Iteration = 0;
   while (DoOneIteration(F, Iteration++))
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index ddab6e0e9e..e54dfb3dc7 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -783,3 +783,29 @@ bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
   return true;
 }
 
+/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
+/// of llvm.dbg.value intrinsics.
+bool llvm::LowerDbgDeclare(Function &F) {
+  DIBuilder DIB(*F.getParent());
+  SmallVector<DbgDeclareInst *, 4> Dbgs;
+  for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
+    for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ++BI) {
+      if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(BI))
+        Dbgs.push_back(DDI);
+    }
+  if (Dbgs.empty())
+    return false;
+
+  for (SmallVector<DbgDeclareInst *, 4>::iterator I = Dbgs.begin(),
+         E = Dbgs.end(); I != E; ++I) {
+    DbgDeclareInst *DDI = *I;
+    if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress())) {
+      for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+           UI != E; ++UI)
+        if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
+          ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+    }
+    DDI->eraseFromParent();
+  }
+  return true;
+}
diff --git a/test/Transforms/InstCombine/debuginfo.ll b/test/Transforms/InstCombine/debuginfo.ll
new file mode 100644
index 0000000000..f6892fc3e1
--- /dev/null
+++ b/test/Transforms/InstCombine/debuginfo.ll
@@ -0,0 +1,57 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
+
+declare i64 @llvm.objectsize.i64(i8*, i1) nounwind readnone
+
+declare i8* @foo(i8*, i32, i64, i64) nounwind
+
+define hidden i8* @foobar(i8* %__dest, i32 %__val, i64 %__len) nounwind inlinehint ssp {
+entry:
+  %__dest.addr = alloca i8*, align 8
+  %__val.addr = alloca i32, align 4
+  %__len.addr = alloca i64, align 8
+  store i8* %__dest, i8** %__dest.addr, align 8, !tbaa !1
+; CHECK-NOT: call void @llvm.dbg.declare
+; CHECK: call void @llvm.dbg.value
+  call void @llvm.dbg.declare(metadata !{i8** %__dest.addr}, metadata !0), !dbg !16
+  store i32 %__val, i32* %__val.addr, align 4, !tbaa !17
+  call void @llvm.dbg.declare(metadata !{i32* %__val.addr}, metadata !7), !dbg !18
+  store i64 %__len, i64* %__len.addr, align 8, !tbaa !19
+  call void @llvm.dbg.declare(metadata !{i64* %__len.addr}, metadata !9), !dbg !20
+  %tmp = load i8** %__dest.addr, align 8, !dbg !21, !tbaa !13
+  %tmp1 = load i32* %__val.addr, align 4, !dbg !21, !tbaa !17
+  %tmp2 = load i64* %__len.addr, align 8, !dbg !21, !tbaa !19
+  %tmp3 = load i8** %__dest.addr, align 8, !dbg !21, !tbaa !13
+  %0 = call i64 @llvm.objectsize.i64(i8* %tmp3, i1 false), !dbg !21
+  %call = call i8* @foo(i8* %tmp, i32 %tmp1, i64 %tmp2, i64 %0), !dbg !21
+  ret i8* %call, !dbg !21
+}
+
+!llvm.dbg.lv.foobar = !{!0, !7, !9}
+!llvm.dbg.sp = !{!1}
+
+!0 = metadata !{i32 590081, metadata !1, metadata !"__dest", metadata !2, i32 16777294, metadata !6, i32 0} ; [ DW_TAG_arg_variable ]
+!1 = metadata !{i32 589870, i32 0, metadata !2, metadata !"foobar", metadata !"foobar", metadata !"", metadata !2, i32 79, metadata !4, i1 true, i1 true, i32 0, i32 0, i32 0, i32 256, i1 true, i8* (i8*, i32, i64)* @foobar} ; [ DW_TAG_subprogram ]
+!2 = metadata !{i32 589865, metadata !"string.h", metadata !"Game", metadata !3} ; [ DW_TAG_file_type ]
+!3 = metadata !{i32 589841, i32 0, i32 12, metadata !"bits.c", metadata !"Game", metadata !"clang version 3.0 (trunk 127710)", i1 true, i1 true, metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
+!4 = metadata !{i32 589845, metadata !2, metadata !"", metadata !2, i32 0, i64 0, i64 0, i32 0, i32 0, i32 0, metadata !5, i32 0, i32 0} ; [ DW_TAG_subroutine_type ]
+!5 = metadata !{metadata !6}
+!6 = metadata !{i32 589839, metadata !3, metadata !"", null, i32 0, i64 64, i64 64, i64 0, i32 0, null} ; [ DW_TAG_pointer_type ]
+!7 = metadata !{i32 590081, metadata !1, metadata !"__val", metadata !2, i32 33554510, metadata !8, i32 0} ; [ DW_TAG_arg_variable ]
+!8 = metadata !{i32 589860, metadata !3, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
+!9 = metadata !{i32 590081, metadata !1, metadata !"__len", metadata !2, i32 50331726, metadata !10, i32 0} ; [ DW_TAG_arg_variable ]
+!10 = metadata !{i32 589846, metadata !3, metadata !"size_t", metadata !2, i32 80, i64 0, i64 0, i64 0, i32 0, metadata !11} ; [ DW_TAG_typedef ]
+!11 = metadata !{i32 589846, metadata !3, metadata !"__darwin_size_t", metadata !2, i32 90, i64 0, i64 0, i64 0, i32 0, metadata !12} ; [ DW_TAG_typedef ]
+!12 = metadata !{i32 589860, metadata !3, metadata !"long unsigned int", null, i32 0, i64 64, i64 64, i64 0, i32 0, i32 7} ; [ DW_TAG_base_type ]
+!13 = metadata !{metadata !"any pointer", metadata !14}
+!14 = metadata !{metadata !"omnipotent char", metadata !15}
+!15 = metadata !{metadata !"Simple C/C++ TBAA", null}
+!16 = metadata !{i32 78, i32 28, metadata !1, null}
+!17 = metadata !{metadata !"int", metadata !14}
+!18 = metadata !{i32 78, i32 40, metadata !1, null}
+!19 = metadata !{metadata !"long", metadata !14}
+!20 = metadata !{i32 78, i32 54, metadata !1, null}
+!21 = metadata !{i32 80, i32 3, metadata !22, null}
+!22 = metadata !{i32 589835, metadata !23, i32 80, i32 3, metadata !2, i32 7} ; [ DW_TAG_lexical_block ]
+!23 = metadata !{i32 589835, metadata !1, i32 79, i32 1, metadata !2, i32 6} ; [ DW_TAG_lexical_block ]