Keep track of incoming debug value of unused argument.

Radar 7927666.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105285 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 72 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 9f8f0c4dd7..833173f244 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -698,6 +698,7 @@ void SelectionDAGBuilder::init(GCFunctionInfo *gfi, AliasAnalysis &aa) {
 /// consumed.
 void SelectionDAGBuilder::clear() {
   NodeMap.clear();
+  UnusedArgNodeMap.clear();
   PendingLoads.clear();
   PendingExports.clear();
   CurDebugLoc = DebugLoc();
@@ -4063,7 +4064,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     } else {
       bool createUndef = false;
       // FIXME : Why not use getValue() directly ?
-      SDValue &N = NodeMap[V];
+      SDValue N = NodeMap[V];
+      if (!N.getNode() && isa<Argument>(V))
+        // Check unused arguments map.
+        N = UnusedArgNodeMap[V];
       if (N.getNode()) {
         if (!EmitFuncArgumentDbgValue(DI, V, Variable, Offset, N)) {
           SDV = DAG.getDbgValue(Variable, N.getNode(),
@@ -6032,6 +6036,12 @@ void SelectionDAGISel::LowerArguments(const BasicBlock *LLVMBB) {
     SmallVector<EVT, 4> ValueVTs;
     ComputeValueVTs(TLI, I->getType(), ValueVTs);
     unsigned NumValues = ValueVTs.size();
+
+    // If this argument is unused then remember its value. It is used to generate
+    // debugging information.
+    if (I->use_empty() && NumValues)
+      SDB->setUnusedArgValue(I, InVals[i]);
+
     for (unsigned Value = 0; Value != NumValues; ++Value) {
       EVT VT = ValueVTs[Value];
       EVT PartVT = TLI.getRegisterType(*CurDAG->getContext(), VT);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 3fcd4b9dc4..86903caa8a 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -88,6 +88,10 @@ class SelectionDAGBuilder {
   DebugLoc CurDebugLoc;
 
   DenseMap<const Value*, SDValue> NodeMap;
+  
+  /// UnusedArgNodeMap - Maps argument value for unused arguments. This is used
+  /// to preserve debug information for incoming arguments.
+  DenseMap<const Value*, SDValue> UnusedArgNodeMap;
 
 public:
   /// PendingLoads - Loads are not emitted to the program immediately.  We bunch
@@ -349,6 +353,12 @@ public:
     N = NewN;
   }
   
+  void setUnusedArgValue(const Value *V, SDValue NewN) {
+    SDValue &N = UnusedArgNodeMap[V];
+    assert(N.getNode() == 0 && "Already set a value for this node!");
+    N = NewN;
+  }
+  
   void GetRegistersForValue(SDISelAsmOperandInfo &OpInfo,
                             std::set<unsigned> &OutputRegs, 
                             std::set<unsigned> &InputRegs);
diff --git a/test/DebugInfo/2010-06-01-DeadArg-DbgInfo.ll b/test/DebugInfo/2010-06-01-DeadArg-DbgInfo.ll
new file mode 100644
index 0000000000..481c12c39d
--- /dev/null
+++ b/test/DebugInfo/2010-06-01-DeadArg-DbgInfo.ll
@@ -0,0 +1,51 @@
+; RUN: llc -O2 < %s | grep this | grep -v undef
+; Test to check that unused argument 'this' is not undefined in debug info.
+
+%struct.foo = type { i32 }
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 (%struct.foo*, i32)* @_ZN3foo3bazEi to i8*)], section "llvm.metadata" ; <[1 x i8*]*> [#uses=0]
+
+define i32 @_ZN3foo3bazEi(%struct.foo* nocapture %this, i32 %x) nounwind readnone optsize noinline ssp align 2 {
+entry:
+  tail call void @llvm.dbg.value(metadata !{%struct.foo* %this}, i64 0, metadata !15)
+  tail call void @llvm.dbg.value(metadata !{i32 %x}, i64 0, metadata !16)
+  %0 = mul nsw i32 %x, 7, !dbg !29                ; <i32> [#uses=1]
+  %1 = add nsw i32 %0, 1, !dbg !29                ; <i32> [#uses=1]
+  ret i32 %1, !dbg !29
+}
+
+declare void @llvm.dbg.value(metadata, i64, metadata) nounwind readnone
+
+!llvm.dbg.lv = !{!0, !14, !15, !16, !17, !24, !25, !28}
+
+!0 = metadata !{i32 524545, metadata !1, metadata !"this", metadata !3, i32 11, metadata !12} ; [ DW_TAG_arg_variable ]
+!1 = metadata !{i32 524334, i32 0, metadata !2, metadata !"bar", metadata !"bar", metadata !"_ZN3foo3barEi", metadata !3, i32 11, metadata !9, i1 false, i1 true, i32 0, i32 0, null, i1 false, i1 true} ; [ DW_TAG_subprogram ]
+!2 = metadata !{i32 524307, metadata !3, metadata !"foo", metadata !3, i32 3, i64 32, i64 32, i64 0, i32 0, null, metadata !5, i32 0, null} ; [ DW_TAG_structure_type ]
+!3 = metadata !{i32 524329, metadata !"foo.cp", metadata !"/tmp/", metadata !4} ; [ DW_TAG_file_type ]
+!4 = metadata !{i32 524305, i32 0, i32 4, metadata !"foo.cp", metadata !"/tmp/", metadata !"4.2.1 LLVM build", i1 true, i1 true, metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
+!5 = metadata !{metadata !6, metadata !1, metadata !8}
+!6 = metadata !{i32 524301, metadata !2, metadata !"y", metadata !3, i32 8, i64 32, i64 32, i64 0, i32 0, metadata !7} ; [ DW_TAG_member ]
+!7 = metadata !{i32 524324, metadata !3, metadata !"int", metadata !3, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
+!8 = metadata !{i32 524334, i32 0, metadata !2, metadata !"baz", metadata !"baz", metadata !"_ZN3foo3bazEi", metadata !3, i32 15, metadata !9, i1 false, i1 true, i32 0, i32 0, null, i1 false, i1 true} ; [ DW_TAG_subprogram ]
+!9 = metadata !{i32 524309, metadata !3, metadata !"", metadata !3, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !10, i32 0, null} ; [ DW_TAG_subroutine_type ]
+!10 = metadata !{metadata !7, metadata !11, metadata !7}
+!11 = metadata !{i32 524303, metadata !3, metadata !"", metadata !3, i32 0, i64 64, i64 64, i64 0, i32 64, metadata !2} ; [ DW_TAG_pointer_type ]
+!12 = metadata !{i32 524326, metadata !3, metadata !"", metadata !3, i32 0, i64 64, i64 64, i64 0, i32 64, metadata !13} ; [ DW_TAG_const_type ]
+!13 = metadata !{i32 524303, metadata !3, metadata !"", metadata !3, i32 0, i64 64, i64 64, i64 0, i32 0, metadata !2} ; [ DW_TAG_pointer_type ]
+!14 = metadata !{i32 524545, metadata !1, metadata !"x", metadata !3, i32 11, metadata !7} ; [ DW_TAG_arg_variable ]
+!15 = metadata !{i32 524545, metadata !8, metadata !"this", metadata !3, i32 15, metadata !12} ; [ DW_TAG_arg_variable ]
+!16 = metadata !{i32 524545, metadata !8, metadata !"x", metadata !3, i32 15, metadata !7} ; [ DW_TAG_arg_variable ]
+!17 = metadata !{i32 524545, metadata !18, metadata !"argc", metadata !3, i32 19, metadata !7} ; [ DW_TAG_arg_variable ]
+!18 = metadata !{i32 524334, i32 0, metadata !3, metadata !"main", metadata !"main", metadata !"main", metadata !3, i32 19, metadata !19, i1 false, i1 true, i32 0, i32 0, null, i1 false, i1 true} ; [ DW_TAG_subprogram ]
+!19 = metadata !{i32 524309, metadata !3, metadata !"", metadata !3, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !20, i32 0, null} ; [ DW_TAG_subroutine_type ]
+!20 = metadata !{metadata !7, metadata !7, metadata !21}
+!21 = metadata !{i32 524303, metadata !3, metadata !"", metadata !3, i32 0, i64 64, i64 64, i64 0, i32 0, metadata !22} ; [ DW_TAG_pointer_type ]
+!22 = metadata !{i32 524303, metadata !3, metadata !"", metadata !3, i32 0, i64 64, i64 64, i64 0, i32 0, metadata !23} ; [ DW_TAG_pointer_type ]
+!23 = metadata !{i32 524324, metadata !3, metadata !"char", metadata !3, i32 0, i64 8, i64 8, i64 0, i32 0, i32 6} ; [ DW_TAG_base_type ]
+!24 = metadata !{i32 524545, metadata !18, metadata !"argv", metadata !3, i32 19, metadata !21} ; [ DW_TAG_arg_variable ]
+!25 = metadata !{i32 524544, metadata !26, metadata !"a", metadata !3, i32 20, metadata !2} ; [ DW_TAG_auto_variable ]
+!26 = metadata !{i32 524299, metadata !27, i32 19, i32 0} ; [ DW_TAG_lexical_block ]
+!27 = metadata !{i32 524299, metadata !18, i32 19, i32 0} ; [ DW_TAG_lexical_block ]
+!28 = metadata !{i32 524544, metadata !26, metadata !"b", metadata !3, i32 21, metadata !7} ; [ DW_TAG_auto_variable ]
+!29 = metadata !{i32 16, i32 0, metadata !30, null}
+!30 = metadata !{i32 524299, metadata !8, i32 15, i32 0} ; [ DW_TAG_lexical_block ]