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1; REQUIRES: x86-registered-target2 3; Test devirtualization through the thin link and backend, ensuring that4; it is only applied when the type test corresponding to a devirtualization5; dominates an indirect call using the same vtable pointer. Indirect6; call promotion and inlining may introduce a guarded indirect call7; that can be promoted, which uses the same vtable address as the fallback8; indirect call that cannot be devirtualized.9 10; The code below illustrates the structure when we started with code like:11;12; class A {13; public:14; virtual int foo() { return 1; }15; virtual int bar() { return 1; }16; };17; class B : public A {18; public:19; virtual int foo();20; virtual int bar();21; };22;23; int foo(A *a) {24; return a->foo(); // ICP profile says most calls are to B::foo()25; }26;27; int B::foo() {28; return bar();29; }30;31; After the compile step, which will perform ICP and a round of inlining, we32; have something like:33; int foo(A *a) {34; if (&a->foo() == B::foo())35; return ((B*)a)->bar(); // Inlined from promoted direct call to B::foo()36; else37; return a->foo();38;39; The inlined code seqence will have a type test against "_ZTS1B",40; which will allow us to devirtualize indirect call ((B*)a)->bar() to B::bar();41; Both that type test and the one for the fallback a->foo() indirect call42; will use the same vtable pointer. Without a dominance check, we could43; incorrectly devirtualize a->foo() to B::foo();44 45; RUN: opt -thinlto-bc -thinlto-split-lto-unit -o %t.o %s46 47; RUN: llvm-lto2 run %t.o -save-temps -pass-remarks=. \48; RUN: -whole-program-visibility \49; RUN: -o %t3 \50; RUN: -r=%t.o,_Z3bazP1A,px \51; RUN: -r=%t.o,_ZN1A3fooEv, \52; RUN: -r=%t.o,_ZN1A3barEv, \53; RUN: -r=%t.o,_ZN1B3fooEv, \54; RUN: -r=%t.o,_ZN1B3barEv, \55; RUN: -r=%t.o,_ZTV1A, \56; RUN: -r=%t.o,_ZTV1B, \57; RUN: -r=%t.o,_ZN1A3fooEv, \58; RUN: -r=%t.o,_ZN1A3barEv, \59; RUN: -r=%t.o,_ZN1B3fooEv, \60; RUN: -r=%t.o,_ZN1B3barEv, \61; RUN: -r=%t.o,_ZTV1A,px \62; RUN: -r=%t.o,_ZTV1B,px 2>&1 | FileCheck %s --check-prefix=REMARK63; RUN: llvm-dis %t3.1.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR64 65; We should only devirtualize the inlined call to bar().66; REMARK-NOT: single-impl: devirtualized a call to _ZN1B3fooEv67; REMARK: single-impl: devirtualized a call to _ZN1B3barEv68; REMARK-NOT: single-impl: devirtualized a call to _ZN1B3fooEv69 70target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"71target triple = "x86_64-grtev4-linux-gnu"72 73%class.A = type { ptr }74%class.B = type { %class.A }75 76@_ZTV1A = linkonce_odr hidden unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr undef, ptr @_ZN1A3fooEv, ptr @_ZN1A3barEv] }, align 8, !type !077@_ZTV1B = hidden unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr undef, ptr @_ZN1B3fooEv, ptr @_ZN1B3barEv] }, align 8, !type !0, !type !178 79define hidden i32 @_Z3bazP1A(ptr %a) local_unnamed_addr {80entry:81 %vtable = load ptr, ptr %a, align 882 %0 = tail call i1 @llvm.type.test(ptr %vtable, metadata !"_ZTS1A")83 tail call void @llvm.assume(i1 %0)84 %1 = load ptr, ptr %vtable, align 885 ; This is the compare instruction inserted by ICP86 %2 = icmp eq ptr %1, @_ZN1B3fooEv87 br i1 %2, label %if.true.direct_targ, label %if.false.orig_indirect88 89; This block contains the promoted and inlined call to B::foo();90; CHECK-IR: if.true.direct_targ: ; preds = %entry91if.true.direct_targ: ; preds = %entry92 %3 = tail call i1 @llvm.type.test(ptr %vtable, metadata !"_ZTS1B")93 tail call void @llvm.assume(i1 %3)94 %vfn.i1 = getelementptr inbounds ptr, ptr %vtable, i64 195 %4 = load ptr, ptr %vfn.i1, align 896; Call to bar() can be devirtualized to call to B::bar(), since it was97; inlined from B::foo() after ICP introduced the guarded promotion.98; CHECK-IR: %call.i = tail call i32 @_ZN1B3barEv(ptr nonnull %a)99 %call.i = tail call i32 %4(ptr %a)100 br label %if.end.icp101 102; This block contains the fallback indirect call a->foo()103; CHECK-IR: if.false.orig_indirect:104if.false.orig_indirect: ; preds = %entry105; Fallback indirect call to foo() cannot be devirtualized.106; CHECK-IR: %call = tail call i32 %107 %call = tail call i32 %1(ptr nonnull %a)108 br label %if.end.icp109 110if.end.icp: ; preds = %if.false.orig_indirect, %if.true.direct_targ111 %5 = phi i32 [ %call, %if.false.orig_indirect ], [ %call.i, %if.true.direct_targ ]112 ret i32 %5113}114 115declare i1 @llvm.type.test(ptr, metadata)116 117declare void @llvm.assume(i1)118 119declare dso_local i32 @_ZN1B3fooEv(ptr %this) unnamed_addr120declare dso_local i32 @_ZN1B3barEv(ptr) unnamed_addr121declare dso_local i32 @_ZN1A3barEv(ptr %this) unnamed_addr122declare dso_local i32 @_ZN1A3fooEv(ptr %this) unnamed_addr123 124!0 = !{i64 16, !"_ZTS1A"}125!1 = !{i64 16, !"_ZTS1B"}126