Do not emit DW_AT_upper_bound and DW_AT_lower_bound for unbouded array.

If lower bound is more then upper bound then consider it is an unbounded array.
An array is unbounded if non-zero lower bound is same as upper bound.
If lower bound and upper bound are zero than array has one element.

llvm-svn: 129156

3 files changed, 50 insertions, 4 deletions

diff --git a/llvm/docs/SourceLevelDebugging.html b/llvm/docs/SourceLevelDebugging.html
index 79ea71ac302..10c78f68888 100644
--- a/llvm/docs/SourceLevelDebugging.html
+++ b/llvm/docs/SourceLevelDebugging.html
@@ -708,7 +708,7 @@ DW_TAG_inheritance      = 28
    <a href="#format_composite_type">composite type</a>.  The low value defines
    the lower bounds typically zero for C/C++.  The high value is the upper
    bounds.  Values are 64 bit.  High - low + 1 is the size of the array.  If low
-   == high the array will be unbounded.</p>
+   > high the array will be unbounded.</p>
 
 </div>
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index bad87c1b558..b9bf37bd5ea 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1237,15 +1237,27 @@ DwarfDebug::getOrCreateTemplateValueParameterDIE(DITemplateValueParameter TPV) {
 
 /// constructSubrangeDIE - Construct subrange DIE from DISubrange.
 void DwarfDebug::constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy){
+  DIE *DW_Subrange = new DIE(dwarf::DW_TAG_subrange_type);
+  addDIEEntry(DW_Subrange, dwarf::DW_AT_type, dwarf::DW_FORM_ref4, IndexTy);
   int64_t L = SR.getLo();
   int64_t H = SR.getHi();
-  DIE *DW_Subrange = new DIE(dwarf::DW_TAG_subrange_type);
 
-  addDIEEntry(DW_Subrange, dwarf::DW_AT_type, dwarf::DW_FORM_ref4, IndexTy);
+  // The L value defines the lower bounds typically zero for C/C++.  The H
+  // value is the upper bounds.  Values are 64 bit.  H - L + 1 is the size
+  // of the array. If L > H the array will be unbounded. If the L is 
+  // non zero and same is H then also the array will be unbounded. If L is
+  // zero and H is zero then the array has one element and in such case do
+  // not emit lower bound.
+
+  if (L > H || (L == H && L != 0)) {
+    // This is an unbounded subrange.
+    Buffer.addChild(DW_Subrange);
+    return;
+  }
+
   if (L)
     addSInt(DW_Subrange, dwarf::DW_AT_lower_bound, 0, L);
   addSInt(DW_Subrange, dwarf::DW_AT_upper_bound, 0, H);
-
   Buffer.addChild(DW_Subrange);
 }
 
diff --git a/llvm/test/DebugInfo/array.ll b/llvm/test/DebugInfo/array.ll
new file mode 100644
index 00000000000..f4aefec8fb3
--- /dev/null
+++ b/llvm/test/DebugInfo/array.ll
@@ -0,0 +1,34 @@
+; RUN: llc -O0 < %s | FileCheck %s
+; Do not emit AT_upper_bound for an unbounded array.
+
+define i32 @main() nounwind ssp {
+entry:
+  %retval = alloca i32, align 4
+  %a = alloca [0 x i32], align 4
+  store i32 0, i32* %retval
+  call void @llvm.dbg.declare(metadata !{[0 x i32]* %a}, metadata !6), !dbg !11
+  ret i32 0, !dbg !12
+}
+
+declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
+
+!llvm.dbg.sp = !{!0}
+
+!0 = metadata !{i32 589870, i32 0, metadata !1, metadata !"main", metadata !"main", metadata !"", metadata !1, i32 3, metadata !3, i1 false, i1 true, i32 0, i32 0, i32 0, i32 0, i1 false, i32 ()* @main, null} ; [ DW_TAG_subprogram ]
+!1 = metadata !{i32 589865, metadata !"array.c", metadata !"/private/tmp", metadata !2} ; [ DW_TAG_file_type ]
+!2 = metadata !{i32 589841, i32 0, i32 12, metadata !"array.c", metadata !"/private/tmp", metadata !"clang version 3.0 (trunk 129138)", i1 true, i1 false, metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
+!3 = metadata !{i32 589845, metadata !1, metadata !"", metadata !1, i32 0, i64 0, i64 0, i32 0, i32 0, i32 0, metadata !4, i32 0, i32 0} ; [ DW_TAG_subroutine_type ]
+!4 = metadata !{metadata !5}
+!5 = metadata !{i32 589860, metadata !2, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
+!6 = metadata !{i32 590080, metadata !7, metadata !"a", metadata !1, i32 4, metadata !8, i32 0} ; [ DW_TAG_auto_variable ]
+!7 = metadata !{i32 589835, metadata !0, i32 3, i32 12, metadata !1, i32 0} ; [ DW_TAG_lexical_block ]
+!8 = metadata !{i32 589825, metadata !2, metadata !"", metadata !2, i32 0, i64 0, i64 32, i32 0, i32 0, metadata !5, metadata !9, i32 0, i32 0} ; [ DW_TAG_array_type ]
+!9 = metadata !{metadata !10}
+;CHECK: DW_TAG_subrange_type
+;CHECK-NEXT: DW_AT_type
+;CHECK-NOT: DW_AT_lower_bound
+;CHECK-NOT: DW_AT_upper_bound
+;CHECK-NEXT: End Of Children Mark
+!10 = metadata !{i32 589857, i64 1, i64 0}        ; [ DW_TAG_subrange_type ]
+!11 = metadata !{i32 4, i32 7, metadata !7, null}
+!12 = metadata !{i32 5, i32 3, metadata !7, null}