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
54 lines
1.9 KiB
LLVM
54 lines
1.9 KiB
LLVM
; RUN: opt -loop-idiom -S < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define void @test1() {
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entry:
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br label %for.body.preheader
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for.body.preheader: ; preds = %for.cond
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br label %for.body
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for.body: ; preds = %for.body, %for.body.preheader
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%indvars.iv = phi i32 [ 0, %for.body.preheader ], [ %indvars.iv.next, %for.body ]
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%add.ptr3 = getelementptr inbounds i32, i32* null, i32 %indvars.iv
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%add.ptr4 = getelementptr inbounds i32, i32* %add.ptr3, i32 1
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%0 = load i32, i32* %add.ptr4, align 4
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store i32 %0, i32* %add.ptr3, align 4
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%indvars.iv.next = add nsw i32 %indvars.iv, 1
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%exitcond = icmp ne i32 %indvars.iv.next, 6
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br i1 %exitcond, label %for.body, label %for.body.preheader
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}
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; CHECK-LABEL: define void @test1(
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; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 null, i8* align 4 inttoptr (i64 4 to i8*), i64 24, i1 false)
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; CHECK-NOT: store
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define void @test1_no_null_opt() #0 {
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entry:
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br label %for.body.preheader
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for.body.preheader: ; preds = %for.cond
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br label %for.body
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for.body: ; preds = %for.body, %for.body.preheader
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%indvars.iv = phi i32 [ 0, %for.body.preheader ], [ %indvars.iv.next, %for.body ]
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%add.ptr3 = getelementptr inbounds i32, i32* null, i32 %indvars.iv
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%add.ptr4 = getelementptr inbounds i32, i32* %add.ptr3, i32 1
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%0 = load i32, i32* %add.ptr4, align 4
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store i32 %0, i32* %add.ptr3, align 4
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%indvars.iv.next = add nsw i32 %indvars.iv, 1
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%exitcond = icmp ne i32 %indvars.iv.next, 6
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br i1 %exitcond, label %for.body, label %for.body.preheader
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}
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; CHECK-LABEL: define void @test1_no_null_opt(
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; CHECK-NOT: call void @llvm.memcpy
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; CHECK: getelementptr
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; CHECK: getelementptr
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; CHECK: load
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; CHECK: store
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attributes #0 = { "null-pointer-is-valid"="true" }
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