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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
241 lines
6.9 KiB
LLVM
241 lines
6.9 KiB
LLVM
; RUN: opt -S -functionattrs -enable-nonnull-arg-prop %s | FileCheck %s
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; RUN: opt -S -passes=function-attrs -enable-nonnull-arg-prop %s | FileCheck %s
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declare nonnull i8* @ret_nonnull()
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; Return a pointer trivially nonnull (call return attribute)
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define i8* @test1() {
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; CHECK: define nonnull i8* @test1
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%ret = call i8* @ret_nonnull()
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ret i8* %ret
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}
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; Return a pointer trivially nonnull (argument attribute)
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define i8* @test2(i8* nonnull %p) {
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; CHECK: define nonnull i8* @test2
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ret i8* %p
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}
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; Given an SCC where one of the functions can not be marked nonnull,
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; can we still mark the other one which is trivially nonnull
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define i8* @scc_binder() {
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; CHECK: define i8* @scc_binder
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call i8* @test3()
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ret i8* null
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}
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define i8* @test3() {
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; CHECK: define nonnull i8* @test3
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call i8* @scc_binder()
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%ret = call i8* @ret_nonnull()
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ret i8* %ret
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}
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; Given a mutual recursive set of functions, we can mark them
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; nonnull if neither can ever return null. (In this case, they
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; just never return period.)
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define i8* @test4_helper() {
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; CHECK: define noalias nonnull i8* @test4_helper
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%ret = call i8* @test4()
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ret i8* %ret
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}
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define i8* @test4() {
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; CHECK: define noalias nonnull i8* @test4
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%ret = call i8* @test4_helper()
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ret i8* %ret
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}
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; Given a mutual recursive set of functions which *can* return null
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; make sure we haven't marked them as nonnull.
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define i8* @test5_helper() {
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; CHECK: define noalias i8* @test5_helper
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%ret = call i8* @test5()
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ret i8* null
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}
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define i8* @test5() {
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; CHECK: define noalias i8* @test5
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%ret = call i8* @test5_helper()
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ret i8* %ret
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}
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; Local analysis, but going through a self recursive phi
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define i8* @test6() {
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entry:
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; CHECK: define nonnull i8* @test6
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%ret = call i8* @ret_nonnull()
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br label %loop
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loop:
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%phi = phi i8* [%ret, %entry], [%phi, %loop]
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br i1 undef, label %loop, label %exit
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exit:
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ret i8* %phi
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}
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; Test propagation of nonnull callsite args back to caller.
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declare void @use1(i8* %x)
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declare void @use2(i8* %x, i8* %y);
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declare void @use3(i8* %x, i8* %y, i8* %z);
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declare void @use1nonnull(i8* nonnull %x);
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declare void @use2nonnull(i8* nonnull %x, i8* nonnull %y);
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declare void @use3nonnull(i8* nonnull %x, i8* nonnull %y, i8* nonnull %z);
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declare i8 @use1safecall(i8* %x) readonly nounwind ; readonly+nounwind guarantees that execution continues to successor
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; Can't extend non-null to parent for any argument because the 2nd call is not guaranteed to execute.
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define void @parent1(i8* %a, i8* %b, i8* %c) {
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; CHECK-LABEL: @parent1(i8* %a, i8* %b, i8* %c)
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; CHECK-NEXT: call void @use3(i8* %c, i8* %a, i8* %b)
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; CHECK-NEXT: call void @use3nonnull(i8* %b, i8* %c, i8* %a)
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; CHECK-NEXT: ret void
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;
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call void @use3(i8* %c, i8* %a, i8* %b)
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call void @use3nonnull(i8* %b, i8* %c, i8* %a)
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ret void
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}
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; Extend non-null to parent for all arguments.
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define void @parent2(i8* %a, i8* %b, i8* %c) {
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; CHECK-LABEL: @parent2(i8* nonnull %a, i8* nonnull %b, i8* nonnull %c)
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; CHECK-NEXT: call void @use3nonnull(i8* %b, i8* %c, i8* %a)
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; CHECK-NEXT: call void @use3(i8* %c, i8* %a, i8* %b)
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; CHECK-NEXT: ret void
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;
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call void @use3nonnull(i8* %b, i8* %c, i8* %a)
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call void @use3(i8* %c, i8* %a, i8* %b)
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ret void
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}
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; Extend non-null to parent for 1st argument.
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define void @parent3(i8* %a, i8* %b, i8* %c) {
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; CHECK-LABEL: @parent3(i8* nonnull %a, i8* %b, i8* %c)
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; CHECK-NEXT: call void @use1nonnull(i8* %a)
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; CHECK-NEXT: call void @use3(i8* %c, i8* %b, i8* %a)
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; CHECK-NEXT: ret void
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;
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call void @use1nonnull(i8* %a)
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call void @use3(i8* %c, i8* %b, i8* %a)
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ret void
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}
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; Extend non-null to parent for last 2 arguments.
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define void @parent4(i8* %a, i8* %b, i8* %c) {
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; CHECK-LABEL: @parent4(i8* %a, i8* nonnull %b, i8* nonnull %c)
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; CHECK-NEXT: call void @use2nonnull(i8* %c, i8* %b)
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; CHECK-NEXT: call void @use2(i8* %a, i8* %c)
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; CHECK-NEXT: call void @use1(i8* %b)
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; CHECK-NEXT: ret void
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;
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call void @use2nonnull(i8* %c, i8* %b)
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call void @use2(i8* %a, i8* %c)
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call void @use1(i8* %b)
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ret void
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}
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; The callsite must execute in order for the attribute to transfer to the parent.
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; It appears benign to extend non-null to the parent in this case, but we can't do that
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; because it would incorrectly propagate the wrong information to its callers.
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define void @parent5(i8* %a, i1 %a_is_notnull) {
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; CHECK-LABEL: @parent5(i8* %a, i1 %a_is_notnull)
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; CHECK-NEXT: br i1 %a_is_notnull, label %t, label %f
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; CHECK: t:
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; CHECK-NEXT: call void @use1nonnull(i8* %a)
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; CHECK-NEXT: ret void
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; CHECK: f:
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; CHECK-NEXT: ret void
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;
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br i1 %a_is_notnull, label %t, label %f
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t:
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call void @use1nonnull(i8* %a)
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ret void
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f:
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ret void
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}
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; The callsite must execute in order for the attribute to transfer to the parent.
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; The volatile load might trap, so there's no guarantee that we'll ever get to the call.
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define i8 @parent6(i8* %a, i8* %b) {
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; CHECK-LABEL: @parent6(i8* %a, i8* %b)
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; CHECK-NEXT: [[C:%.*]] = load volatile i8, i8* %b
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; CHECK-NEXT: call void @use1nonnull(i8* %a)
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; CHECK-NEXT: ret i8 [[C]]
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;
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%c = load volatile i8, i8* %b
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call void @use1nonnull(i8* %a)
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ret i8 %c
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}
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; The nonnull callsite is guaranteed to execute, so the argument must be nonnull throughout the parent.
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define i8 @parent7(i8* %a) {
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; CHECK-LABEL: @parent7(i8* nonnull %a)
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; CHECK-NEXT: [[RET:%.*]] = call i8 @use1safecall(i8* %a)
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; CHECK-NEXT: call void @use1nonnull(i8* %a)
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; CHECK-NEXT: ret i8 [[RET]]
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;
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%ret = call i8 @use1safecall(i8* %a)
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call void @use1nonnull(i8* %a)
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ret i8 %ret
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}
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; Make sure that an invoke works similarly to a call.
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declare i32 @esfp(...)
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define i1 @parent8(i8* %a, i8* %bogus1, i8* %b) personality i8* bitcast (i32 (...)* @esfp to i8*){
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; CHECK-LABEL: @parent8(i8* nonnull %a, i8* nocapture readnone %bogus1, i8* nonnull %b)
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; CHECK-NEXT: entry:
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; CHECK-NEXT: invoke void @use2nonnull(i8* %a, i8* %b)
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; CHECK-NEXT: to label %cont unwind label %exc
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; CHECK: cont:
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* %b, null
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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; CHECK: exc:
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; CHECK-NEXT: [[LP:%.*]] = landingpad { i8*, i32 }
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; CHECK-NEXT: filter [0 x i8*] zeroinitializer
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; CHECK-NEXT: unreachable
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;
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entry:
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invoke void @use2nonnull(i8* %a, i8* %b)
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to label %cont unwind label %exc
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cont:
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%null_check = icmp eq i8* %b, null
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ret i1 %null_check
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exc:
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%lp = landingpad { i8*, i32 }
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filter [0 x i8*] zeroinitializer
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unreachable
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}
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; CHECK: define nonnull i32* @gep1(
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define i32* @gep1(i32* %p) {
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%q = getelementptr inbounds i32, i32* %p, i32 1
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ret i32* %q
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}
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define i32* @gep1_no_null_opt(i32* %p) #0 {
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; Should't be able to derive nonnull based on gep.
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; CHECK: define i32* @gep1_no_null_opt(
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%q = getelementptr inbounds i32, i32* %p, i32 1
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ret i32* %q
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}
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; CHECK: define i32 addrspace(3)* @gep2(
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define i32 addrspace(3)* @gep2(i32 addrspace(3)* %p) {
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%q = getelementptr inbounds i32, i32 addrspace(3)* %p, i32 1
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ret i32 addrspace(3)* %q
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}
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attributes #0 = { "null-pointer-is-valid"="true" }
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