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fcd1037fbe
For the following motivating example
bool c();
void f();
bool start() {
bool result = c();
if (!c()) {
result = false;
goto exit;
}
f();
result = true;
exit:
return result;
}
we would previously generate a single DW_AT_const_value(1) because
only the DBG_VALUE in the second-to-last basic block survived
codegen. This patch improves the heuristic used to determine when a
DBG_VALUE is available at the beginning of its variable's enclosing
lexical scope:
- Stop giving singular constants blanket permission to take over the
entire scope. There is still a special case for constants in the
function prologue that we also miight want to retire later.
- Use the lexical scope information to determine available-at-entry
instead of proximity to the function prologue.
After this patch we generate a location list with a more accurate
narrower availability for the constant true value. As a pleasant side
effect, we also generate inline locations instead of location lists
where a loacation covers the entire range of the enclosing lexical
scope.
Measured on compiling llc with four targets this doesn't have an
effect on compile time and reduces the size of the debug info for llc
by ~600K.
rdar://problem/30286912
llvm-svn: 305599
113 lines
5.7 KiB
LLVM
113 lines
5.7 KiB
LLVM
; RUN: llc %s -filetype=obj -o - | llvm-dwarfdump - | FileCheck %s
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;
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; // Compile with -O1
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; typedef struct {
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; int a;
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; int b;
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; } Inner;
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;
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; typedef struct {
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; Inner inner[2];
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; } Outer;
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;
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; int foo(Outer outer) {
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; Inner i1 = outer.inner[1];
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; return i1.a;
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; }
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;
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; CHECK: DW_TAG_formal_parameter [3]
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; CHECK-NEXT: DW_AT_location [DW_FORM_data4] ([[LOC1:.*]])
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; CHECK-NEXT: DW_AT_name {{.*}}"outer"
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; CHECK: DW_TAG_variable
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; CHECK-NEXT: DW_AT_location
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; rsi, piece 0x00000004
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; CHECK-SAME: 54 93 04
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; CHECK-NEXT: "i1"
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;
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; CHECK: .debug_loc
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; CHECK: [[LOC1]]: Beginning address offset: 0x0000000000000000
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; CHECK-NEXT: Ending address offset: 0x0000000000000004
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; rdi, piece 0x00000008, piece 0x00000004, rsi, piece 0x00000004
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; CHECK-NEXT: Location description: 55 93 08 93 04 54 93 04
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; This location is split into two ranges with identical locations
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; because it comes from a DBG_VALUE %RSI followed by a DBG_VALUE %ESI.
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; CHECK: Beginning address offset: 0x0000000000000004
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; CHECK-NEXT: Ending address offset: 0x0000000000000008
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; CHECK-NEXT: Location description: 55 93 08 93 04 54 93 04
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;
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; ModuleID = '/Volumes/Data/llvm/test/DebugInfo/X86/sroasplit-2.ll'
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.9.0"
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; Function Attrs: nounwind ssp uwtable
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define i32 @foo(i64 %outer.coerce0, i64 %outer.coerce1) #0 !dbg !4 {
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call void @llvm.dbg.value(metadata i64 %outer.coerce0, i64 0, metadata !24, metadata !25), !dbg !26
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call void @llvm.dbg.declare(metadata !{null}, metadata !27, metadata !28), !dbg !26
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call void @llvm.dbg.value(metadata i64 %outer.coerce1, i64 0, metadata !29, metadata !30), !dbg !26
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call void @llvm.dbg.declare(metadata !{null}, metadata !31, metadata !32), !dbg !26
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; The 'trunc' generates no extra code, thus i1 is visible throughout its scope.
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%outer.sroa.1.8.extract.trunc = trunc i64 %outer.coerce1 to i32, !dbg !33
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call void @llvm.dbg.value(metadata i32 %outer.sroa.1.8.extract.trunc, i64 0, metadata !34, metadata !35), !dbg !33
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%outer.sroa.1.12.extract.shift = lshr i64 %outer.coerce1, 32, !dbg !33
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%outer.sroa.1.12.extract.trunc = trunc i64 %outer.sroa.1.12.extract.shift to i32, !dbg !33
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call void @llvm.dbg.value(metadata i64 %outer.sroa.1.12.extract.shift, i64 0, metadata !34, metadata !35), !dbg !33
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call void @llvm.dbg.value(metadata i32 %outer.sroa.1.12.extract.trunc, i64 0, metadata !34, metadata !35), !dbg !33
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call void @llvm.dbg.declare(metadata !{null}, metadata !34, metadata !35), !dbg !33
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ret i32 %outer.sroa.1.8.extract.trunc, !dbg !36
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}
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; Function Attrs: nounwind readnone
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declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
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; Function Attrs: nounwind
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declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) #2
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; Function Attrs: nounwind readnone
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declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
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attributes #0 = { nounwind ssp uwtable "no-frame-pointer-elim"="true" }
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attributes #1 = { nounwind readnone }
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attributes #2 = { nounwind }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!21, !22}
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!llvm.ident = !{!23}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
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!1 = !DIFile(filename: "sroasplit-2.c", directory: "")
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!2 = !{}
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!4 = distinct !DISubprogram(name: "foo", line: 10, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 10, file: !1, scope: !5, type: !6, variables: !2)
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!5 = !DIFile(filename: "sroasplit-2.c", directory: "")
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!6 = !DISubroutineType(types: !7)
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!7 = !{!8, !9}
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!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!9 = !DIDerivedType(tag: DW_TAG_typedef, name: "Outer", line: 8, file: !1, baseType: !10)
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!10 = !DICompositeType(tag: DW_TAG_structure_type, line: 6, size: 128, align: 32, file: !1, elements: !11)
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!11 = !{!12}
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!12 = !DIDerivedType(tag: DW_TAG_member, name: "inner", line: 7, size: 128, align: 32, file: !1, scope: !10, baseType: !13)
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!13 = !DICompositeType(tag: DW_TAG_array_type, size: 128, align: 32, baseType: !14, elements: !19)
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!14 = !DIDerivedType(tag: DW_TAG_typedef, name: "Inner", line: 4, file: !1, baseType: !15)
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!15 = !DICompositeType(tag: DW_TAG_structure_type, line: 1, size: 64, align: 32, file: !1, elements: !16)
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!16 = !{!17, !18}
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!17 = !DIDerivedType(tag: DW_TAG_member, name: "a", line: 2, size: 32, align: 32, file: !1, scope: !15, baseType: !8)
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!18 = !DIDerivedType(tag: DW_TAG_member, name: "b", line: 3, size: 32, align: 32, offset: 32, file: !1, scope: !15, baseType: !8)
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!19 = !{!20}
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!20 = !DISubrange(count: 2)
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!21 = !{i32 2, !"Dwarf Version", i32 2}
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!22 = !{i32 1, !"Debug Info Version", i32 3}
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!23 = !{!"clang version 3.5.0 "}
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!24 = !DILocalVariable(name: "outer", line: 10, arg: 1, scope: !4, file: !5, type: !9)
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!25 = !DIExpression(DW_OP_LLVM_fragment, 0, 64)
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!26 = !DILocation(line: 10, scope: !4)
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!27 = !DILocalVariable(name: "outer", line: 10, arg: 1, scope: !4, file: !5, type: !9)
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!28 = !DIExpression(DW_OP_LLVM_fragment, 64, 64)
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!29 = !DILocalVariable(name: "outer", line: 10, arg: 1, scope: !4, file: !5, type: !9)
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!30 = !DIExpression(DW_OP_LLVM_fragment, 96, 32)
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!31 = !DILocalVariable(name: "outer", line: 10, arg: 1, scope: !4, file: !5, type: !9)
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!32 = !DIExpression(DW_OP_LLVM_fragment, 64, 32)
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!33 = !DILocation(line: 11, scope: !4)
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!34 = !DILocalVariable(name: "i1", line: 11, scope: !4, file: !5, type: !14)
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!35 = !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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!36 = !DILocation(line: 12, scope: !4)
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