forked from OSchip/llvm-project
56 lines
2.5 KiB
LLVM
56 lines
2.5 KiB
LLVM
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; RUN: opt < %s -globaldce -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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declare dso_local noalias nonnull i8* @_Znwm(i64)
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declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata)
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; %struct.A is a C++ struct with two virtual functions, A::foo and A::bar. The
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; !vcall_visibility metadata is set on the vtable, so we know that all virtual
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; calls through this vtable are visible and use the @llvm.type.checked.load
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; intrinsic. Function test_A makes a call to A::foo, but there is no call to
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; A::bar anywhere, so A::bar can be deleted, and its vtable slot replaced with
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; null.
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%struct.A = type { i32 (...)** }
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; The pointer to A::bar in the vtable can be removed, because it will never be
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; loaded. We replace it with null to keep the layout the same. Because it is at
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; the end of the vtable we could potentially shrink the vtable, but don't
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; currently do that.
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; CHECK: @_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*), i8* null] }
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@_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*), i8* bitcast (i32 (%struct.A*)* @_ZN1A3barEv to i8*)] }, align 8, !type !0, !type !1, !type !2, !vcall_visibility !3
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; A::foo is called, so must be retained.
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; CHECK: define internal i32 @_ZN1A3fooEv(
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define internal i32 @_ZN1A3fooEv(%struct.A* nocapture readnone %this) {
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entry:
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ret i32 42
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}
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; A::bar is not used, so can be deleted.
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; CHECK-NOT: define internal i32 @_ZN1A3barEv(
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define internal i32 @_ZN1A3barEv(%struct.A* nocapture readnone %this) {
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entry:
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ret i32 1337
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}
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define dso_local i32 @test_A() {
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entry:
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%call = tail call i8* @_Znwm(i64 8)
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%0 = bitcast i8* %call to %struct.A*
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%1 = bitcast i8* %call to i32 (...)***
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store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %1, align 8
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%2 = tail call { i8*, i1 } @llvm.type.checked.load(i8* bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i8*), i32 0, metadata !"_ZTS1A"), !nosanitize !9
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%3 = extractvalue { i8*, i1 } %2, 0, !nosanitize !9
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%4 = bitcast i8* %3 to i32 (%struct.A*)*, !nosanitize !9
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%call1 = tail call i32 %4(%struct.A* nonnull %0)
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ret i32 %call1
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}
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!0 = !{i64 16, !"_ZTS1A"}
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!1 = !{i64 16, !"_ZTSM1AFivE.virtual"}
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!2 = !{i64 24, !"_ZTSM1AFivE.virtual"}
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!3 = !{i64 2}
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!9 = !{}
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