1228becf7d
This patch deduces `noundef` attributes for return values. IIUC, a function returns `noundef` values iff all of its return values are guaranteed not to be `undef` or `poison`. Definition of `noundef` from LangRef: ``` noundef This attribute applies to parameters and return values. If the value representation contains any undefined or poison bits, the behavior is undefined. Note that this does not refer to padding introduced by the type’s storage representation. ``` Alive2: https://alive2.llvm.org/ce/z/g8Eis6 Compile-time impact: http://llvm-compile-time-tracker.com/compare.php?from=30dcc33c4ea3ab50397a7adbe85fe977d4a400bd&to=c5e8738d4bfbf1e97e3f455fded90b791f223d74&stat=instructions:u |stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang| |--|--|--|--|--|--|--| |+0.01%|+0.01%|-0.01%|+0.01%|+0.03%|-0.04%|+0.01%| The motivation of this patch is to reduce the number of `freeze` insts and enable more optimizations.
103 lines
4.5 KiB
LLVM
103 lines
4.5 KiB
LLVM
; ModuleID = 'array.c'
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;
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; From (clang -g -c -O0):
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;
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; void f(int* p) {
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; p[0] = 42;
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; }
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;
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; int main(int argc, char** argv) {
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; int array[4] = { 0, 1, 2, 3 };
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; f(array);
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; return array[0];
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; }
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;
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; RUN: opt %s -O2 -S -o - | FileCheck %s
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; RUN: opt --try-experimental-debuginfo-iterators %s -O2 -S -o - | FileCheck %s
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; Test that we correctly lower dbg.declares for arrays.
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;
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; CHECK: define noundef i32 @main
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; CHECK: call void @llvm.dbg.value(metadata i32 42, metadata ![[ARRAY:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32))
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; CHECK: ![[ARRAY]] = !DILocalVariable(name: "array",{{.*}} line: 6
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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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@main.array = private unnamed_addr constant [4 x i32] [i32 0, i32 1, i32 2, i32 3], align 16
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; Function Attrs: nounwind ssp uwtable
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define void @f(ptr %p) #0 !dbg !4 {
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entry:
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%p.addr = alloca ptr, align 8
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store ptr %p, ptr %p.addr, align 8
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call void @llvm.dbg.declare(metadata ptr %p.addr, metadata !19, metadata !DIExpression()), !dbg !20
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%0 = load ptr, ptr %p.addr, align 8, !dbg !21
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store i32 42, ptr %0, align 4, !dbg !21
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ret void, !dbg !22
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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 ssp uwtable
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define i32 @main(i32 %argc, ptr %argv) #0 !dbg !10 {
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entry:
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%retval = alloca i32, align 4
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%argc.addr = alloca i32, align 4
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%argv.addr = alloca ptr, align 8
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%array = alloca [4 x i32], align 16
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store i32 0, ptr %retval
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store i32 %argc, ptr %argc.addr, align 4
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call void @llvm.dbg.declare(metadata ptr %argc.addr, metadata !23, metadata !DIExpression()), !dbg !24
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store ptr %argv, ptr %argv.addr, align 8
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call void @llvm.dbg.declare(metadata ptr %argv.addr, metadata !25, metadata !DIExpression()), !dbg !24
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call void @llvm.dbg.declare(metadata ptr %array, metadata !26, metadata !DIExpression()), !dbg !30
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call void @llvm.memcpy.p0.p0.i64(ptr align 16 %array, ptr align 16 @main.array, i64 16, i1 false), !dbg !30
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call void @f(ptr %array), !dbg !31
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%0 = load i32, ptr %array, align 4, !dbg !32
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ret i32 %0, !dbg !32
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}
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; Function Attrs: nounwind
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declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture readonly, i64, i1) #2
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attributes #0 = { nounwind ssp uwtable }
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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 = !{!16, !17}
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!llvm.ident = !{!18}
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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: "array.c", directory: "")
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!2 = !{}
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!4 = distinct !DISubprogram(name: "f", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, retainedNodes: !2)
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!5 = !DIFile(filename: "array.c", directory: "")
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!6 = !DISubroutineType(types: !7)
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!7 = !{null, !8}
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!8 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !9)
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!9 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!10 = distinct !DISubprogram(name: "main", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 5, file: !1, scope: !5, type: !11, retainedNodes: !2)
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!11 = !DISubroutineType(types: !12)
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!12 = !{!9, !9, !13}
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!13 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !14)
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!14 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !15)
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!15 = !DIBasicType(tag: DW_TAG_base_type, name: "char", size: 8, align: 8, encoding: DW_ATE_signed_char)
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!16 = !{i32 2, !"Dwarf Version", i32 2}
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!17 = !{i32 1, !"Debug Info Version", i32 3}
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!18 = !{!"clang version 3.5.0 "}
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!19 = !DILocalVariable(name: "p", line: 1, arg: 1, scope: !4, file: !5, type: !8)
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!20 = !DILocation(line: 1, scope: !4)
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!21 = !DILocation(line: 2, scope: !4)
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!22 = !DILocation(line: 3, scope: !4)
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!23 = !DILocalVariable(name: "argc", line: 5, arg: 1, scope: !10, file: !5, type: !9)
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!24 = !DILocation(line: 5, scope: !10)
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!25 = !DILocalVariable(name: "argv", line: 5, arg: 2, scope: !10, file: !5, type: !13)
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!26 = !DILocalVariable(name: "array", line: 6, scope: !10, file: !5, type: !27)
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!27 = !DICompositeType(tag: DW_TAG_array_type, size: 128, align: 32, baseType: !9, elements: !28)
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!28 = !{!29}
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!29 = !DISubrange(count: 4)
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!30 = !DILocation(line: 6, scope: !10)
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!31 = !DILocation(line: 7, scope: !10)
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!32 = !DILocation(line: 8, scope: !10)
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