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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
28 lines
649 B
LLVM
28 lines
649 B
LLVM
; RUN: opt < %s -globalopt -S | FileCheck %s
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@G = internal global void ()* null ; <void ()**> [#uses=2]
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; CHECK: global
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define internal void @Actual() {
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; CHECK-LABEL: Actual(
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ret void
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}
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define void @init() {
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; CHECK-LABEL: init(
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; CHECK: store void ()* @Actual, void ()** @G
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store void ()* @Actual, void ()** @G
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ret void
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}
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define void @doit() #0 {
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; CHECK-LABEL: doit(
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; CHECK: %FP = load void ()*, void ()** @G
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; CHECK: call void %FP()
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%FP = load void ()*, void ()** @G ; <void ()*> [#uses=1]
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call void %FP( )
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ret void
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}
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attributes #0 = { "null-pointer-is-valid"="true" }
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