Commit 31441a3e authored by Teresa Johnson's avatar Teresa Johnson
Browse files

[ThinLTO/WPD] Fix index-based WPD for alias vtables 

Summary:
A recent fix in D69452 fixed index based WPD in the presence of
available_externally vtables. It added a cast of the vtable def
summary to a GlobalVarSummary. However, in some cases one def may be an
alias, in which case we need to get the base object before casting,
otherwise we will crash.

Reviewers: evgeny777, steven_wu, aganea

Subscribers: mehdi_amini, inglorion, hiraditya, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71040
parent 810b28ed

llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp

+1 −1
Original line number Diff line number Diff line
@@ -869,7 +869,7 @@ bool DevirtIndex::tryFindVirtualCallTargets( 
        LocalFound = true;

      }

      if (!GlobalValue::isAvailableExternallyLinkage(S->linkage()))

        VS = cast<GlobalVarSummary>(S.get());

        VS = cast<GlobalVarSummary>(S->getBaseObject());

    }

    if (!VS->isLive())

      continue;

llvm/test/ThinLTO/X86/Inputs/devirt_alias.ll

0 → 100644
+15 −0
Original line number Diff line number Diff line 
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"

target triple = "x86_64-grtev4-linux-gnu"



%struct.D = type { i32 (...)** }



@some_name = constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.D*, i32)* @_ZN1D1mEi to i8*)] }, !type !3

@_ZTV1D = alias { [3 x i8*] }, { [3 x i8*] }* @some_name



define i32 @_ZN1D1mEi(%struct.D* %this, i32 %a) #0 {

   ret i32 0;

}



attributes #0 = { noinline optnone }



!3 = !{i64 16, !"_ZTS1D"}

llvm/test/ThinLTO/X86/devirt_alias.ll

0 → 100644
+58 −0
Original line number Diff line number Diff line 
; REQUIRES: x86-registered-target



; Test index-based devirtualization when one copy is an alias.



; Generate unsplit module with summary for ThinLTO index-based WPD.

; RUN: opt -thinlto-bc -o %t3.o %s

; RUN: opt -thinlto-bc -o %t4.o %p/Inputs/devirt_alias.ll



; RUN: llvm-lto2 run %t3.o %t4.o -save-temps -pass-remarks=. \

; RUN:   -wholeprogramdevirt-print-index-based \

; RUN:   -o %t5 \

; RUN:   -r=%t3.o,test,px \

; RUN:   -r=%t3.o,_ZTV1D, \

; RUN:   -r=%t3.o,_ZN1D1mEi, \

; RUN:   -r=%t4.o,_ZN1D1mEi,p \

; RUN:   -r=%t4.o,_ZTV1D,px \

; RUN:   -r=%t4.o,some_name,px \

; RUN:   2>&1 | FileCheck %s --check-prefix=REMARK --check-prefix=PRINT

; RUN: llvm-dis %t5.1.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR1



; PRINT-DAG: Devirtualized call to {{.*}} (_ZN1D1mEi)



; REMARK-DAG: single-impl: devirtualized a call to _ZN1D1mEi



target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"

target triple = "x86_64-grtev4-linux-gnu"



%struct.D = type { i32 (...)** }



@_ZTV1D = linkonce_odr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.D*, i32)* @_ZN1D1mEi to i8*)] }, !type !3



; CHECK-IR1-LABEL: define i32 @test

define i32 @test(%struct.D* %obj2, i32 %a) {

entry:

  %0 = bitcast %struct.D* %obj2 to i8***

  %vtable2 = load i8**, i8*** %0

  %1 = bitcast i8** %vtable2 to i8*

  %p2 = call i1 @llvm.type.test(i8* %1, metadata !"_ZTS1D")

  call void @llvm.assume(i1 %p2)



  %2 = bitcast i8** %vtable2 to i32 (%struct.D*, i32)**

  %fptr33 = load i32 (%struct.D*, i32)*, i32 (%struct.D*, i32)** %2, align 8



  ; Check that the call was devirtualized.

  ; CHECK-IR1: %call4 = tail call i32 @_ZN1D1mEi

  %call4 = tail call i32 %fptr33(%struct.D* nonnull %obj2, i32 %a)

  ret i32 %call4

}

; CHECK-IR1-LABEL: ret i32

; CHECK-IR1-LABEL: }



declare i1 @llvm.type.test(i8*, metadata)

declare void @llvm.assume(i1)

declare i32 @_ZN1D1mEi(%struct.D* %this, i32 %a)



attributes #0 = { noinline optnone }



!3 = !{i64 16, !"_ZTS1D"}