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1; RUN: opt < %s -passes=globaldce -S | FileCheck %s2 3target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"4 5declare dso_local noalias nonnull ptr @_Znwm(i64)6declare { ptr, i1 } @llvm.type.checked.load(ptr, i32, metadata)7 8; %struct.A is a C++ struct with two virtual functions, A::foo and A::bar. The9; !vcall_visibility metadata is set on the vtable, so we know that all virtual10; calls through this vtable are visible and use the @llvm.type.checked.load11; intrinsic. Function test_A makes a call to A::foo, but there is no call to12; A::bar anywhere, so A::bar can be deleted, and its vtable slot replaced with13; null.14 15%struct.A = type { ptr }16 17; The pointer to A::bar in the vtable can be removed, because it will never be18; loaded. We replace it with null to keep the layout the same. Because it is at19; the end of the vtable we could potentially shrink the vtable, but don't20; currently do that.21; CHECK: @_ZTV1A = internal unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr null, ptr @_ZN1A3fooEv, ptr null] }22@_ZTV1A = internal unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr null, ptr @_ZN1A3fooEv, ptr @_ZN1A3barEv] }, align 8, !type !0, !type !1, !type !2, !vcall_visibility !323 24; A::foo is called, so must be retained.25; CHECK: define internal i32 @_ZN1A3fooEv(26define internal i32 @_ZN1A3fooEv(ptr nocapture readnone %this) {27entry:28 ret i32 4229}30 31; A::bar is not used, so can be deleted.32; CHECK-NOT: define internal i32 @_ZN1A3barEv(33define internal i32 @_ZN1A3barEv(ptr nocapture readnone %this) {34entry:35 ret i32 133736}37 38define dso_local i32 @test_A() {39entry:40 %call = tail call ptr @_Znwm(i64 8)41 store ptr getelementptr inbounds inrange(-16, 16) ({ [4 x ptr] }, ptr @_ZTV1A, i64 0, i32 0, i64 2), ptr %call, align 842 %0 = tail call { ptr, i1 } @llvm.type.checked.load(ptr getelementptr inbounds inrange(-16, 16) ({ [4 x ptr] }, ptr @_ZTV1A, i64 0, i32 0, i64 2), i32 0, metadata !"_ZTS1A"), !nosanitize !943 %1 = extractvalue { ptr, i1 } %0, 0, !nosanitize !944 %call1 = tail call i32 %1(ptr nonnull %call)45 ret i32 %call146}47 48!llvm.module.flags = !{!4}49 50!0 = !{i64 16, !"_ZTS1A"}51!1 = !{i64 16, !"_ZTSM1AFivE.virtual"}52!2 = !{i64 24, !"_ZTSM1AFivE.virtual"}53!3 = !{i64 2}54!4 = !{i32 1, !"Virtual Function Elim", i32 1}55!9 = !{}56