274bcbc139
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
118 lines
5.0 KiB
LLVM
118 lines
5.0 KiB
LLVM
; REQUIRES: object-emission
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;
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; RUN: llc -mtriple=x86_64-unknown-linux-gnu -O0 -filetype=obj < %s > %t
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; RUN: llvm-dwarfdump %t | FileCheck %s
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; Test case derived from compiling the following source with clang -g:
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;
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; namespace pr14763 {
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; struct foo {
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; foo(const foo&);
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; };
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;
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; foo func(foo f) {
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; return f; // reference 'f' for now because otherwise we hit another bug
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; }
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;
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; void sink(void*);
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;
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; void func2(bool b, foo g) {
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; if (b)
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; sink(&g); // reference 'f' for now because otherwise we hit another bug
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; }
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; }
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; CHECK: debug_info contents
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; 0x74 is DW_OP_breg4, showing that the parameter is accessed indirectly
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; (with a zero offset) from the register parameter.
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; CHECK: DW_AT_location {{.*}} 74 00 06
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; CHECK-NOT: DW_TAG
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; CHECK: DW_AT_name{{.*}} = "f"
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;
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; CHECK: DW_AT_location{{.*}}([[G_LOC:0x[0-9]*]])
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; CHECK-NOT: DW_TAG
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; CHECK: DW_AT_name{{.*}} = "g"
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;
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; CHECK: debug_loc contents
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; CHECK: [[G_LOC]]: Beginning
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; CHECK-NEXT: Ending
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; CHECK-NEXT: Location description: 74 00
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%"struct.pr14763::foo" = type { i8 }
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; Function Attrs: uwtable
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define void @_ZN7pr147634funcENS_3fooE(%"struct.pr14763::foo"* noalias sret %agg.result, %"struct.pr14763::foo"* %f) #0 !dbg !4 {
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entry:
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call void @llvm.dbg.declare(metadata %"struct.pr14763::foo"* %f, metadata !22, metadata !DIExpression(DW_OP_deref)), !dbg !24
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call void @_ZN7pr147633fooC1ERKS0_(%"struct.pr14763::foo"* %agg.result, %"struct.pr14763::foo"* %f), !dbg !25
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ret void, !dbg !25
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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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declare void @_ZN7pr147633fooC1ERKS0_(%"struct.pr14763::foo"*, %"struct.pr14763::foo"*) #2
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; Function Attrs: uwtable
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define void @_ZN7pr147635func2EbNS_3fooE(i1 zeroext %b, %"struct.pr14763::foo"* %g) #0 !dbg !17 {
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entry:
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%b.addr = alloca i8, align 1
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%frombool = zext i1 %b to i8
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store i8 %frombool, i8* %b.addr, align 1
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call void @llvm.dbg.declare(metadata i8* %b.addr, metadata !26, metadata !DIExpression()), !dbg !27
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call void @llvm.dbg.declare(metadata %"struct.pr14763::foo"* %g, metadata !28, metadata !DIExpression(DW_OP_deref)), !dbg !27
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%0 = load i8, i8* %b.addr, align 1, !dbg !29
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%tobool = trunc i8 %0 to i1, !dbg !29
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br i1 %tobool, label %if.then, label %if.end, !dbg !29
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if.then: ; preds = %entry
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%1 = bitcast %"struct.pr14763::foo"* %g to i8*, !dbg !31
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call void @_ZN7pr147634sinkEPv(i8* %1), !dbg !31
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br label %if.end, !dbg !31
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if.end: ; preds = %if.then, %entry
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ret void, !dbg !32
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}
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declare void @_ZN7pr147634sinkEPv(i8*)
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attributes #0 = { uwtable }
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attributes #1 = { nounwind readnone }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!21, !33}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.4 ", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
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!1 = !DIFile(filename: "pass.cpp", directory: "/tmp")
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!2 = !{}
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!4 = distinct !DISubprogram(name: "func", linkageName: "_ZN7pr147634funcENS_3fooE", line: 6, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 6, file: !1, scope: !5, type: !6, variables: !2)
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!5 = !DINamespace(name: "pr14763", scope: null)
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!6 = !DISubroutineType(types: !7)
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!7 = !{!8, !8}
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!8 = !DICompositeType(tag: DW_TAG_structure_type, name: "foo", line: 2, size: 8, align: 8, file: !1, scope: !5, elements: !9)
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!9 = !{!10}
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!10 = !DISubprogram(name: "foo", line: 3, isLocal: false, isDefinition: false, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 3, file: !1, scope: !8, type: !11)
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!11 = !DISubroutineType(types: !12)
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!12 = !{null, !13, !14}
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!13 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, flags: DIFlagArtificial | DIFlagObjectPointer, baseType: !8)
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!14 = !DIDerivedType(tag: DW_TAG_reference_type, baseType: !15)
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!15 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !8)
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!17 = distinct !DISubprogram(name: "func2", linkageName: "_ZN7pr147635func2EbNS_3fooE", line: 12, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 12, file: !1, scope: !5, type: !18, variables: !2)
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!18 = !DISubroutineType(types: !19)
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!19 = !{null, !20, !8}
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!20 = !DIBasicType(tag: DW_TAG_base_type, name: "bool", size: 8, align: 8, encoding: DW_ATE_boolean)
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!21 = !{i32 2, !"Dwarf Version", i32 3}
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!22 = !DILocalVariable(name: "f", line: 6, arg: 1, scope: !4, file: !23, type: !8)
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!23 = !DIFile(filename: "pass.cpp", directory: "/tmp")
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!24 = !DILocation(line: 6, scope: !4)
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!25 = !DILocation(line: 7, scope: !4)
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!26 = !DILocalVariable(name: "b", line: 12, arg: 1, scope: !17, file: !23, type: !20)
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!27 = !DILocation(line: 12, scope: !17)
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!28 = !DILocalVariable(name: "g", line: 12, arg: 2, scope: !17, file: !23, type: !8)
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!29 = !DILocation(line: 13, scope: !30)
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!30 = distinct !DILexicalBlock(line: 13, column: 0, file: !1, scope: !17)
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!31 = !DILocation(line: 14, scope: !30)
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!32 = !DILocation(line: 15, scope: !17)
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!33 = !{i32 1, !"Debug Info Version", i32 3}
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