77eeac3d9e
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
35 lines
1.1 KiB
LLVM
35 lines
1.1 KiB
LLVM
; RUN: opt -globalopt -S < %s | FileCheck %s
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; CHECK: @Y
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; CHECK: section ".foo"
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%struct.xyz = type { double, i32 }
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@Y = internal global %struct.xyz* null ,section ".foo" ; <%struct.xyz**> [#uses=2]
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@numf2s = external global i32 ; <i32*> [#uses=1]
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define void @init_net() #0 {
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; CHECK-LABEL: init_net(
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; CHECK: load i32, i32* @numf2s
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; CHECK: call i8* @malloc
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; CHECK: store %struct.xyz* {{.*}}, %struct.xyz** @Y
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entry:
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%0 = load i32, i32* @numf2s, align 4 ; <i32> [#uses=1]
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%mallocsize2 = shl i32 %0, 4 ; <i32> [#uses=1]
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%malloccall3 = tail call i8* @malloc(i32 %mallocsize2) ; <i8*> [#uses=1]
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%1 = bitcast i8* %malloccall3 to %struct.xyz* ; <%struct.xyz*> [#uses=1]
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store %struct.xyz* %1, %struct.xyz** @Y, align 8
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ret void
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}
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define %struct.xyz* @load_train() #0 {
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; CHECK-LABEL: load_train(
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; CHECK: load %struct.xyz*, %struct.xyz** @Y
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entry:
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%0 = load %struct.xyz*, %struct.xyz** @Y, align 8 ; <%struct.xyz*> [#uses=0]
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ret %struct.xyz* %0
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}
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declare noalias i8* @malloc(i32)
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attributes #0 = { "null-pointer-is-valid"="true" }
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