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647946fa14
Summary: Support for this option is needed for building Linux kernel. This is a very frequently requested feature by kernel developers. More details : https://lkml.org/lkml/2018/4/4/601 GCC option description for -fdelete-null-pointer-checks: This Assume that programs cannot safely dereference null pointers, and that no code or data element resides at address zero. -fno-delete-null-pointer-checks is the inverse of this implying that null pointer dereferencing is not undefined. This feature is implemented in LLVM IR in this CL as the function attribute "null-pointer-is-valid"="true" in IR (Under review at D47894). The CL updates several passes that assumed null pointer dereferencing is undefined to not optimize when the "null-pointer-is-valid"="true" attribute is present. Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv Reviewed By: efriedma, george.burgess.iv Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits Differential Revision: https://reviews.llvm.org/D47895 llvm-svn: 336613
25 lines
1.1 KiB
LLVM
25 lines
1.1 KiB
LLVM
; RUN: opt -S -simplifycfg < %s | FileCheck %s
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define void @foo() nounwind ssp #0 !dbg !0 {
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; CHECK: store i32 42, i32* null
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; CHECK-NOT: call void @llvm.trap()
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; CHECK: ret void
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store i32 42, i32* null, !dbg !5
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ret void, !dbg !7
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}
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attributes #0 = { "null-pointer-is-valid"="true" }
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!10}
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!0 = distinct !DISubprogram(name: "foo", line: 3, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, unit: !2, file: !8, scope: !1, type: !3)
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!1 = !DIFile(filename: "foo.c", directory: "/private/tmp")
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!2 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "Apple clang version 3.0 (tags/Apple/clang-206.1) (based on LLVM 3.0svn)", isOptimized: true, emissionKind: FullDebug, file: !8, enums: !{}, retainedTypes: !{})
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!3 = !DISubroutineType(types: !4)
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!4 = !{null}
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!5 = !DILocation(line: 4, column: 2, scope: !6)
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!6 = distinct !DILexicalBlock(line: 3, column: 12, file: !8, scope: !0)
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!7 = !DILocation(line: 5, column: 1, scope: !6)
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!8 = !DIFile(filename: "foo.c", directory: "/private/tmp")
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!10 = !{i32 1, !"Debug Info Version", i32 3}
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