[llvm] r227827 - Debug Info: Relax assertion in isUnsignedDIType() to allow floats to be
David Blaikie
dblaikie at gmail.com
Mon Feb 2 11:26:41 PST 2015
On Mon, Feb 2, 2015 at 11:24 AM, Adrian Prantl <aprantl at apple.com> wrote:
>
> On Feb 2, 2015, at 10:39 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
>
> On Mon, Feb 2, 2015 at 10:31 AM, Adrian Prantl <aprantl at apple.com> wrote:
>
>> Author: adrian
>> Date: Mon Feb 2 12:31:58 2015
>> New Revision: 227827
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=227827&view=rev
>> Log:
>> Debug Info: Relax assertion in isUnsignedDIType() to allow floats to be
>> described by integer constants. This is a bit ugly, but if the source
>> language allows arbitrary type casting, the debug info must follow suit.
>>
>> For example:
>> void foo() {
>> float a;
>> *(int *)&a = 0;
>> }
>> For the curious: SROA replaces the float alloca with an i32 alloca, which
>> is then optimized away and described via dbg.value(i32 0, ...).
>>
>
> Not sure this is the right answer - even if the IR looks like that, it may
> be that we need to convert the constant back to the appropriate type before
> emitting the debug info?
>
> Sounds reasonable, but if I understand the code in DwarfUnit correctly,
> there would not be any difference in the output:
>
> } else if (DVInsn->getOperand(0).isFPImm())
> addConstantFPValue(*VariableDie, DVInsn->getOperand(0));
> ->
> /// addConstantFPValue - Add constant value entry in variable DIE.
> void DwarfUnit::addConstantFPValue(DIE &Die, const ConstantFP *CFP) {
> // Pass this down to addConstantValue as an unsigned bag of bits.
> addConstantValue(Die, CFP->getValueAPF().bitcastToAPInt(), true);
> }
> ->
> void DwarfUnit::addConstantValue(DIE &Die, const APInt &Val, bool
> Unsigned) {
> ->
> void DwarfUnit::addConstantValue(DIE &Die, const APInt &Val, DIType Ty) {
> addConstantValue(Die, Val, isUnsignedDIType(DD, Ty));
> }
>
Ah, fair enough - it's just bits at the end (udata/sdata, not some
float_data or somesuch).
The lack of canonicalization is just a bit worrying - anywhere in the
compiler that can lead to differences in behavior & pain.
- David
>
> -- adrian
>
>
> - David
>
>
>>
>> Added:
>> llvm/trunk/test/DebugInfo/X86/float_const.ll
>> Modified:
>> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=227827&r1=227826&r2=227827&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Mon Feb 2 12:31:58
>> 2015
>> @@ -606,6 +606,7 @@ static bool isUnsignedDIType(DwarfDebug
>> Encoding == dwarf::DW_ATE_unsigned_char ||
>> Encoding == dwarf::DW_ATE_signed ||
>> Encoding == dwarf::DW_ATE_signed_char ||
>> + Encoding == dwarf::DW_ATE_float ||
>> Encoding == dwarf::DW_ATE_UTF || Encoding ==
>> dwarf::DW_ATE_boolean ||
>> (Ty.getTag() == dwarf::DW_TAG_unspecified_type &&
>> Ty.getName() == "decltype(nullptr)")) &&
>>
>> Added: llvm/trunk/test/DebugInfo/X86/float_const.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/float_const.ll?rev=227827&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/DebugInfo/X86/float_const.ll (added)
>> +++ llvm/trunk/test/DebugInfo/X86/float_const.ll Mon Feb 2 12:31:58 2015
>> @@ -0,0 +1,55 @@
>> +; RUN: llc < %s -filetype=obj | llvm-dwarfdump -debug-dump=info - |
>> FileCheck %s
>> +; from (at -Os):
>> +; void foo() {
>> +; float a = 3.14;
>> +; *(int *)&a = 0;
>> +; }
>> +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
>> +target triple = "x86_64-apple-macosx10.10.0"
>> +
>> +; Function Attrs: nounwind optsize readnone uwtable
>> +define void @foo() #0 {
>> +entry:
>> + tail call void @llvm.dbg.declare(metadata float* undef, metadata !13,
>> metadata !19), !dbg !20
>> + tail call void @llvm.dbg.value(metadata i32 1078523331, i64 0,
>> metadata !13, metadata !19), !dbg !20
>> + tail call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !13,
>> metadata !19), !dbg !20
>> +; CHECK: DW_AT_const_value [DW_FORM_sdata] (0)
>> +; CHECK-NEXT: DW_AT_name {{.*}}"a"
>> + ret void, !dbg !21
>> +}
>> +
>> +; Function Attrs: nounwind readnone
>> +declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
>> +
>> +; Function Attrs: nounwind readnone
>> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
>> +
>> +attributes #0 = { nounwind optsize readnone uwtable }
>> +attributes #1 = { nounwind readnone }
>> +
>> +!llvm.dbg.cu = !{!0}
>> +!llvm.module.flags = !{!15, !16, !17}
>> +!llvm.ident = !{!18}
>> +
>> +!0 = !{!"0x11\0012\00clang version 3.7.0 (trunk
>> 227686)\001\00\000\00\001", !1, !2, !3, !6, !2, !2} ; [ DW_TAG_compile_unit
>> ] [foo.c] [DW_LANG_C99]
>> +!1 = !{!"foo.c", !""}
>> +!2 = !{}
>> +!3 = !{!4}
>> +!4 = !{!"0xf\00\000\0064\0064\000\000", null, null, !5} ; [
>> DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from int]
>> +!5 = !{!"0x24\00int\000\0032\0032\000\000\005", null, null} ; [
>> DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc
>> DW_ATE_signed]
>> +!6 = !{!7}
>> +!7 = !{!"0x2e\00foo\00foo\00\001\000\001\000\000\000\001\001", !8, !9,
>> !10, null, void ()* @foo, null, null, !12} ; [ DW_TAG_subprogram ] [line 1]
>> [def] [foo]
>> +!8 = !{!"foo.c", !""}
>> +!9 = !{!"0x29", !8} ; [ DW_TAG_file_type ]
>> +!10 = !{!"0x15\00\000\000\000\000\000\000", null, null, null, !11, null,
>> null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset
>> 0] [from ]
>> +!11 = !{null}
>> +!12 = !{!13}
>> +!13 = !{!"0x100\00a\002\000", !7, !9, !14} ; [
>> DW_TAG_auto_variable ] [a] [line 2]
>> +!14 = !{!"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]
>> +!15 = !{i32 2, !"Dwarf Version", i32 2}
>> +!16 = !{i32 2, !"Debug Info Version", i32 2}
>> +!17 = !{i32 1, !"PIC Level", i32 2}
>> +!18 = !{!"clang version 3.7.0 (trunk 227686)"}
>> +!19 = !{!"0x102"} ; [ DW_TAG_expression ]
>> +!20 = !MDLocation(line: 2, column: 9, scope: !7)
>> +!21 = !MDLocation(line: 4, column: 1, scope: !7)
>>
>>
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