2009-11-07 08:16:28 +08:00
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; RUN: opt < %s -globalopt -S | FileCheck %s
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2009-11-03 23:29:06 +08:00
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target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
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2004-10-11 13:00:12 +08:00
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llvm: Add support for "-fno-delete-null-pointer-checks"
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
2018-07-10 06:27:23 +08:00
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@G = internal global i32* null ; <i32**> [#uses=4]
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2009-11-07 08:16:28 +08:00
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; CHECK-NOT: global
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2004-10-11 13:00:12 +08:00
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2008-03-01 17:15:35 +08:00
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define void @init() {
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2009-11-07 08:16:28 +08:00
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%malloccall = tail call i8* @malloc(i64 4) ; <i8*> [#uses=1]
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%P = bitcast i8* %malloccall to i32* ; <i32*> [#uses=1]
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2008-03-01 17:15:35 +08:00
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store i32* %P, i32** @G
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2015-02-28 05:17:42 +08:00
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%GV = load i32*, i32** @G ; <i32*> [#uses=1]
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2008-03-01 17:15:35 +08:00
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store i32 0, i32* %GV
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|
ret void
|
2004-10-11 13:00:12 +08:00
|
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|
}
|
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|
2009-11-07 08:16:28 +08:00
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|
declare noalias i8* @malloc(i64)
|
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|
2008-03-01 17:15:35 +08:00
|
|
|
define i32 @get() {
|
2015-02-28 05:17:42 +08:00
|
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|
%GV = load i32*, i32** @G ; <i32*> [#uses=1]
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%V = load i32, i32* %GV ; <i32> [#uses=1]
|
2008-03-01 17:15:35 +08:00
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|
ret i32 %V
|
2009-11-07 08:16:28 +08:00
|
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|
; CHECK: ret i32 0
|
2004-10-11 13:00:12 +08:00
|
|
|
}
|
2008-03-01 17:15:35 +08:00
|
|
|
|
llvm: Add support for "-fno-delete-null-pointer-checks"
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
2018-07-10 06:27:23 +08:00
|
|
|
define void @foo(i64 %Size) nounwind noinline #0 {
|
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|
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entry:
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|
%0 = load i32*, i32** @G, align 4
|
|
|
|
ret void
|
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|
}
|
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|
attributes #0 = { "null-pointer-is-valid"="true" }
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