Doesn't really matter.<div><br></div><div>-eric</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Dec 4, 2012 at 8:52 AM, Chris Lattner <span dir="ltr"><<a href="mailto:clattner@apple.com" target="_blank">clattner@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Does it make sense to only emit this attribute in the ambiguous case?<br>
<span class="HOEnZb"><font color="#888888"><br>
-Chris<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
On Dec 3, 2012, at 10:21 PM, Bill Wendling <<a href="mailto:isanbard@gmail.com">isanbard@gmail.com</a>> wrote:<br>
<br>
> Author: void<br>
> Date: Tue Dec  4 00:21:27 2012<br>
> New Revision: 169219<br>
><br>
> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=169219&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=169219&view=rev</a><br>
> Log:<br>
> Add a 'count' field to the DWARF subrange.<br>
><br>
> The count field is necessary because there isn't a difference between the 'lo'<br>
> and 'hi' attributes for a one-element array and a zero-element array. When the<br>
> count is '0', we know that this is a zero-element array. When it's >=1, then<br>
> it's a normal constant sized array. When it's -1, then the array is unbounded.<br>
><br>
> Added:<br>
>    cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp<br>
> Modified:<br>
>    cfe/trunk/lib/CodeGen/CGDebugInfo.cpp<br>
>    cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp<br>
><br>
> Modified: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=169219&r1=169218&r2=169219&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=169219&r1=169218&r2=169219&view=diff</a><br>

> ==============================================================================<br>
> --- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp (original)<br>
> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Tue Dec  4 00:21:27 2012<br>
> @@ -1475,6 +1475,7 @@<br>
>   llvm::DIType ElementTy = getOrCreateType(Ty->getElementType(), Unit);<br>
>   int64_t NumElems = Ty->getNumElements();<br>
>   int64_t LowerBound = 0;<br>
> +  int64_t Count = NumElems;<br>
>   if (NumElems == 0)<br>
>     // If number of elements are not known then this is an unbounded array.<br>
>     // Use Low = 1, Hi = 0 to express such arrays.<br>
> @@ -1482,7 +1483,8 @@<br>
>   else<br>
>     --NumElems;<br>
><br>
> -  llvm::Value *Subscript = DBuilder.getOrCreateSubrange(LowerBound, NumElems);<br>
> +  llvm::Value *Subscript = DBuilder.getOrCreateSubrange(LowerBound, NumElems,<br>
> +                                                        Count);<br>
>   llvm::DIArray SubscriptArray = DBuilder.getOrCreateArray(Subscript);<br>
><br>
>   uint64_t Size = CGM.getContext().getTypeSize(Ty);<br>
> @@ -1523,19 +1525,30 @@<br>
>   SmallVector<llvm::Value *, 8> Subscripts;<br>
>   QualType EltTy(Ty, 0);<br>
>   while ((Ty = dyn_cast<ArrayType>(EltTy))) {<br>
> +    // If the number of elements is known, then count is that number. Otherwise,<br>
> +    // it's -1. This allows us to represent a subrange with an array of 0<br>
> +    // elements, like this:<br>
> +    //<br>
> +    //   struct foo {<br>
> +    //     int x[0];<br>
> +    //   };<br>
>     int64_t UpperBound = 0;<br>
>     int64_t LowerBound = 0;<br>
> +    int64_t Count = -1;<br>
>     if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(Ty)) {<br>
> -      if (CAT->getSize().getZExtValue())<br>
> -        UpperBound = CAT->getSize().getZExtValue() - 1;<br>
> -    } else<br>
> +      Count = CAT->getSize().getZExtValue();<br>
> +      if (Count)<br>
> +        UpperBound = Count - 1;<br>
> +    } else {<br>
>       // This is an unbounded array. Use Low = 1, Hi = 0 to express such<br>
>       // arrays.<br>
>       LowerBound = 1;<br>
> +    }<br>
><br>
>     // FIXME: Verify this is right for VLAs.<br>
>     Subscripts.push_back(DBuilder.getOrCreateSubrange(LowerBound,<br>
> -                                                      UpperBound));<br>
> +                                                      UpperBound,<br>
> +                                                      Count));<br>
>     EltTy = Ty->getElementType();<br>
>   }<br>
><br>
><br>
> Modified: cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp?rev=169219&r1=169218&r2=169219&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp?rev=169219&r1=169218&r2=169219&view=diff</a><br>

> ==============================================================================<br>
> --- cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp (original)<br>
> +++ cfe/trunk/test/CodeGenCXX/debug-info-flex-member.cpp Tue Dec  4 00:21:27 2012<br>
> @@ -1,6 +1,6 @@<br>
> // RUN: %clang_cc1 -emit-llvm -g -triple x86_64-apple-darwin %s -o - | FileCheck %s<br>
><br>
> -// CHECK: metadata !{i32 {{.*}}, i64 1, i64 0}        ; [ DW_TAG_subrange_type ]<br>
> +// CHECK: metadata !{i32 {{.*}}, i64 1, i64 0, i64 -1}        ; [ DW_TAG_subrange_type ]<br>
><br>
> struct StructName {<br>
>   int member[];<br>
><br>
> Added: cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp?rev=169219&view=auto" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp?rev=169219&view=auto</a><br>

> ==============================================================================<br>
> --- cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp (added)<br>
> +++ cfe/trunk/test/CodeGenCXX/debug-info-zero-length-arrays.cpp Tue Dec  4 00:21:27 2012<br>
> @@ -0,0 +1,16 @@<br>
> +// RUN: %clang -fverbose-asm -g -O0 -S %s -o - | FileCheck %s<br>
> +// <rdar://problem/12566646><br>
> +<br>
> +class A {<br>
> +  int x[];<br>
> +};<br>
> +A a;<br>
> +<br>
> +// CHECK:      Abbrev [3] 0x2d:0x3 DW_TAG_base_type<br>
> +// CHECK-NEXT:   DW_AT_byte_size<br>
> +// CHECK-NEXT:     DW_AT_encoding<br>
> +// CHECK-NEXT:   Abbrev [4] 0x30:0xb DW_TAG_array_type<br>
> +// CHECK-NEXT:     DW_AT_type<br>
> +// CHECK-NEXT:     Abbrev [5] 0x35:0x5 DW_TAG_subrange_type<br>
> +// CHECK-NEXT:       DW_AT_type<br>
> +// CHECK-NEXT:   End Of Children Mark<br>
><br>
><br>
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</div></div></blockquote></div><br></div>