Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp =================================================================== --- lib/CodeGen/AsmPrinter/DwarfDebug.cpp +++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp @@ -1722,6 +1722,18 @@ Streamer.EmitInt8(dwarf::DW_OP_constu, "DW_OP_constu"); Streamer.EmitULEB128(Value.getInt()); } + // The proper way to describe a constant value is + // DW_OP_constu , DW_OP_stack_value. + // Unfortunately, DW_OP_stack_value was not available until DWARF-4, + // so we will continue to generate DW_OP_constu for DWARF-2 + // and DWARF-3. Technically, this is incorrect since DW_OP_const + // actually describes a value at a constant addess, not a constant value. + // However, in the past there was no better way to describe a constant + // value, so the producers and consumers started to rely on heuristics + // to disambiguate the value vs. location status of the expression. + // See PR21176 for more details. + if (getDwarfVersion() >= 4) + Streamer.EmitInt8(dwarf::DW_OP_stack_value, "DW_OP_stack_value"); } else if (Value.isLocation()) { MachineLocation Loc = Value.getLoc(); DIExpression Expr = Value.getExpression(); Index: test/DebugInfo/incorrect-variable-debugloc1.ll =================================================================== --- test/DebugInfo/incorrect-variable-debugloc1.ll +++ test/DebugInfo/incorrect-variable-debugloc1.ll @@ -0,0 +1,77 @@ +; REQUIRES: object-emission +; This test is failing for powerpc64, because a location list for the +; variable 'c' is not generated at all. Temporary making this test to XFAIL +; for powerpc, until PR21881 is fixed. +; XFAIL: powerpc64 + +; RUN: %llc_dwarf -O2 -dwarf-version 2 -filetype=obj < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DWARF23 +; RUN: %llc_dwarf -O2 -dwarf-version 3 -filetype=obj < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DWARF23 +; RUN: %llc_dwarf -O2 -dwarf-version 4 -filetype=obj < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DWARF4 + +; This is a test for PR21176. +; DW_OP_const doesn't describe a constant value, but a value at a constant address. +; The proper way to describe a constant value is DW_OP_constu , DW_OP_stack_value. + +; Generated with clang -S -emit-llvm -g -O2 test.cpp + +; extern int func(); +; +; int main() +; { +; volatile int c = 13; +; c = func(); +; return c; +; } + +; DWARF23: Location description: 10 0d {{$}} +; DWARF4: Location description: 10 0d 9f + +; Function Attrs: uwtable +define i32 @main() #0 { +entry: + %c = alloca i32, align 4 + tail call void @llvm.dbg.value(metadata !15, i64 0, metadata !10, metadata !16), !dbg !17 + store volatile i32 13, i32* %c, align 4, !dbg !18 + %call = tail call i32 @_Z4funcv(), !dbg !19 + tail call void @llvm.dbg.value(metadata !{i32 %call}, i64 0, metadata !10, metadata !16), !dbg !17 + store volatile i32 %call, i32* %c, align 4, !dbg !19 + tail call void @llvm.dbg.value(metadata !{i32* %c}, i64 0, metadata !10, metadata !16), !dbg !17 + %c.0.c.0. = load volatile i32* %c, align 4, !dbg !20 + ret i32 %c.0.c.0., !dbg !20 +} + +declare i32 @_Z4funcv() #1 + +; Function Attrs: nounwind readnone +declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2 + +attributes #0 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" } +attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" } +attributes #2 = { nounwind readnone } + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!12, !13} +!llvm.ident = !{!14} + +!0 = metadata !{metadata !"0x11\004\00clang version 3.6.0 (trunk 223522)\001\00\000\00\001", metadata !1, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2} ; [ DW_TAG_compile_unit ] [/home/kromanova/ngh/ToT_latest/llvm/test/DebugInfo/test.cpp] [DW_LANG_C_plus_plus] +!1 = metadata !{metadata !"test.cpp", metadata !"/home/kromanova/ngh/ToT_latest/llvm/test/DebugInfo"} +!2 = metadata !{} +!3 = metadata !{metadata !4} +!4 = metadata !{metadata !"0x2e\00main\00main\00\003\000\001\000\000\00256\001\004", metadata !1, metadata !5, metadata !6, null, i32 ()* @main, null, null, metadata !9} ; [ DW_TAG_subprogram ] [line 3] [def] [scope 4] [main] +!5 = metadata !{metadata !"0x29", metadata !1} ; [ DW_TAG_file_type ] [/home/kromanova/ngh/ToT_latest/llvm/test/DebugInfo/test.cpp] +!6 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ] +!7 = metadata !{metadata !8} +!8 = metadata !{metadata !"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] +!9 = metadata !{metadata !10} +!10 = metadata !{metadata !"0x100\00c\005\000", metadata !4, metadata !5, metadata !11} ; [ DW_TAG_auto_variable ] [c] [line 5] +!11 = metadata !{metadata !"0x35\00\000\000\000\000\000", null, null, metadata !8} ; [ DW_TAG_volatile_type ] [line 0, size 0, align 0, offset 0] [from int] +!12 = metadata !{i32 2, metadata !"Dwarf Version", i32 2} +!13 = metadata !{i32 2, metadata !"Debug Info Version", i32 2} +!14 = metadata !{metadata !"clang version 3.6.0 (trunk 223522)"} +!15 = metadata !{i32 13} +!16 = metadata !{metadata !"0x102"} ; [ DW_TAG_expression ] +!17 = metadata !{i32 5, i32 16, metadata !4, null} +!18 = metadata !{i32 5, i32 3, metadata !4, null} +!19 = metadata !{i32 6, i32 7, metadata !4, null} +!20 = metadata !{i32 7, i32 3, metadata !4, null} +