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8920d6a40a
Summary: First patch to support Safe Whole Program Devirtualization Enablement, see RFC here: http://lists.llvm.org/pipermail/llvm-dev/2019-December/137543.html Always emit !vcall_visibility metadata under -fwhole-program-vtables, and not just for -fvirtual-function-elimination. The vcall visibility metadata will (in a subsequent patch) be used to communicate to WPD which vtables are safe to devirtualize, and we will optionally convert the metadata to hidden visibility at link time. Subsequent follow on patches will help enable this by adding vcall_visibility metadata to the ThinLTO summaries, and always emit type test intrinsics under -fwhole-program-vtables (and not just for vtables with hidden visibility). In order to do this safely with VFE, since for VFE all vtable loads must be type checked loads which will no longer be the case, this patch adds a new "Virtual Function Elim" module flag to communicate to GlobalDCE whether to perform VFE using the vcall_visibility metadata. One additional advantage of using the vcall_visibility metadata to drive more WPD at LTO link time is that we can use the same mechanism to enable more aggressive VFE at LTO link time as well. The link time option proposed in the RFC will convert vcall_visibility metadata to hidden (aka linkage unit visibility), which combined with -fvirtual-function-elimination will allow it to be done more aggressively at LTO link time under the same conditions. Reviewers: pcc, ostannard, evgeny777, steven_wu Subscribers: mehdi_amini, Prazek, hiraditya, dexonsmith, davidxl, cfe-commits, llvm-commits Tags: #clang, #llvm Differential Revision: https://reviews.llvm.org/D71907
66 lines
3.1 KiB
LLVM
66 lines
3.1 KiB
LLVM
; RUN: opt -S -globalsplit %s | FileCheck %s
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; RUN: opt -S -passes=globalsplit %s | FileCheck %s
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target datalayout = "e-p:64:64"
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target triple = "x86_64-unknown-linux-gnu"
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; CHECK: @vtt = constant [3 x i8*] [i8* bitcast ([2 x i8* ()*]* @global.0 to i8*), i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i32 0, i32 1) to i8*), i8* bitcast ([1 x i8* ()*]* @global.1 to i8*)]
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@vtt = constant [3 x i8*] [
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i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*),
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i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 1) to i8*),
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i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 1, i32 0) to i8*)
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]
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; CHECK-NOT: @global =
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; CHECK: @global.0 = private constant [2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2], !type [[T1:![0-9]+]], !type [[T2:![0-9]+]], !type [[T3:![0-9]+]], !vcall_visibility [[VIS:![0-9]+$]]
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; CHECK: @global.1 = private constant [1 x i8* ()*] [i8* ()* @f3], !type [[T4:![0-9]+]], !type [[T5:![0-9]+]], !vcall_visibility [[VIS$]]
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; CHECK-NOT: @global =
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@global = internal constant { [2 x i8* ()*], [1 x i8* ()*] } {
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[2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2],
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[1 x i8* ()*] [i8* ()* @f3]
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}, !type !0, !type !1, !type !2, !type !3, !type !4, !vcall_visibility !5
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; CHECK: define i8* @f1()
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define i8* @f1() {
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; CHECK-NEXT: ret i8* bitcast ([2 x i8* ()*]* @global.0 to i8*)
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ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*)
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}
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; CHECK: define i8* @f2()
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define i8* @f2() {
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; CHECK-NEXT: ret i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i32 0, i32 1) to i8*)
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ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 1) to i8*)
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}
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; CHECK: define i8* @f3()
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define i8* @f3() {
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; CHECK-NEXT: ret i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i64 1, i32 0) to i8*)
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ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 2) to i8*)
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}
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; CHECK: define i8* @f4()
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define i8* @f4() {
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; CHECK-NEXT: ret i8* bitcast ([1 x i8* ()*]* @global.1 to i8*)
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ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 1, i32 0) to i8*)
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}
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define void @foo() {
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%p = call i1 @llvm.type.test(i8* null, metadata !"")
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ret void
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}
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declare i1 @llvm.type.test(i8*, metadata) nounwind readnone
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; CHECK: [[T1]] = !{i32 0, !"foo"}
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; CHECK: [[T2]] = !{i32 15, !"bar"}
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; CHECK: [[T3]] = !{i32 16, !"a"}
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; CHECK: [[VIS]] = !{i64 2}
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; CHECK: [[T4]] = !{i32 1, !"b"}
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; CHECK: [[T5]] = !{i32 8, !"c"}
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!0 = !{i32 0, !"foo"}
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!1 = !{i32 15, !"bar"}
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!2 = !{i32 16, !"a"}
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!3 = !{i32 17, !"b"}
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!4 = !{i32 24, !"c"}
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!5 = !{i64 2}
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