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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
55 lines
2.2 KiB
LLVM
55 lines
2.2 KiB
LLVM
; RUN: opt < %s -globalopt -S | FileCheck %s
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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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%struct.foo = type { i32, i32 }
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@X = internal global %struct.foo* null ; <%struct.foo**> [#uses=2]
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; CHECK: @X
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; CHECK-NOT: @X.f0
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define void @bar(i32 %Size) nounwind noinline #0 {
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; CHECK-LABEL: @bar(
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entry:
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%malloccall = tail call i8* @malloc(i64 8000000) ; <i8*> [#uses=1]
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%tmp = bitcast i8* %malloccall to [1000000 x %struct.foo]* ; <[1000000 x %struct.foo]*> [#uses=1]
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%.sub = getelementptr [1000000 x %struct.foo], [1000000 x %struct.foo]* %tmp, i32 0, i32 0 ; <%struct.foo*> [#uses=1]
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store %struct.foo* %.sub, %struct.foo** @X, align 4
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ret void
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}
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declare noalias i8* @malloc(i64)
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define i32 @baz() nounwind readonly noinline #0 {
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; CHECK-LABEL: @baz(
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bb1.thread:
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%tmpLD1 = load %struct.foo*, %struct.foo** @X, align 4 ; <%struct.foo*> [#uses=1]
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; CHECK: load %struct.foo*, %struct.foo** @X, align 4
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br label %bb1
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bb1: ; preds = %bb1, %bb1.thread
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%tmp = phi %struct.foo* [%tmpLD1, %bb1.thread ], [ %tmpLD2, %bb1 ] ; <i32> [#uses=2]
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; CHECK: %tmp = phi %struct.foo* [ %tmpLD1, %bb1.thread ], [ %tmpLD2, %bb1 ]
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%i.0.reg2mem.0 = phi i32 [ 0, %bb1.thread ], [ %indvar.next, %bb1 ] ; <i32> [#uses=2]
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%sum.0.reg2mem.0 = phi i32 [ 0, %bb1.thread ], [ %tmp3, %bb1 ] ; <i32> [#uses=1]
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%tmp1 = getelementptr %struct.foo, %struct.foo* %tmp, i32 %i.0.reg2mem.0, i32 0 ; <i32*> [#uses=1]
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%tmp2 = load i32, i32* %tmp1, align 4 ; <i32> [#uses=1]
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; CHECK: load i32, i32* %tmp1, align 4
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%tmp6 = add i32 %tmp2, %sum.0.reg2mem.0 ; <i32> [#uses=2]
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%tmp4 = getelementptr %struct.foo, %struct.foo* %tmp, i32 %i.0.reg2mem.0, i32 1 ; <i32*> [#uses=1]
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%tmp5 = load i32 , i32 * %tmp4
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; CHECK: load i32, i32* %tmp4
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%tmp3 = add i32 %tmp5, %tmp6
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%indvar.next = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=2]
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%tmpLD2 = load %struct.foo*, %struct.foo** @X, align 4 ; <%struct.foo*> [#uses=1]
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; CHECK: load %struct.foo*, %struct.foo** @X, align 4
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%exitcond = icmp eq i32 %indvar.next, 1200 ; <i1> [#uses=1]
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br i1 %exitcond, label %bb2, label %bb1
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bb2: ; preds = %bb1
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ret i32 %tmp3
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}
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attributes #0 = { "null-pointer-is-valid"="true" }
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