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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
32 lines
1.1 KiB
LLVM
32 lines
1.1 KiB
LLVM
; RUN: opt < %s -instcombine -S | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
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target triple = "x86_64-apple-darwin10.0.0"
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define void @func(i8* %i) nounwind ssp {
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; CHECK-LABEL: @func(
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; CHECK: @__strcpy_chk(i8* nonnull %arraydecay, i8* %i, i64 32)
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entry:
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%s = alloca [32 x i8], align 16
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%arraydecay = getelementptr inbounds [32 x i8], [32 x i8]* %s, i32 0, i32 0
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%call = call i8* @__strcpy_chk(i8* %arraydecay, i8* %i, i64 32)
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call void @func2(i8* %arraydecay)
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ret void
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}
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define void @func_no_null_opt(i8* %i) nounwind ssp #0 {
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; CHECK-LABEL: @func_no_null_opt(
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; CHECK: @__strcpy_chk(i8* %arraydecay, i8* %i, i64 32)
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entry:
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%s = alloca [32 x i8], align 16
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%arraydecay = getelementptr inbounds [32 x i8], [32 x i8]* %s, i32 0, i32 0
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%call = call i8* @__strcpy_chk(i8* %arraydecay, i8* %i, i64 32)
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call void @func2(i8* %arraydecay)
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ret void
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}
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declare i8* @__strcpy_chk(i8*, i8*, i64) nounwind
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declare void @func2(i8*)
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attributes #0 = { "null-pointer-is-valid"="true" }
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