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Fix one-after-the-end type metadata handling in globalsplit.
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Itanium ABI may have an address point one byte after the end of a
vtable. When such vtable global is split, the !type metadata needs to
follow the right vtable.

Differential Revision: https://reviews.llvm.org/D30716

llvm-svn: 297236
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eugenis committed Mar 7, 2017
1 parent 1dc735b commit 7a5cfa9
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Showing 2 changed files with 23 additions and 8 deletions.
11 changes: 10 additions & 1 deletion llvm/lib/Transforms/IPO/GlobalSplit.cpp
Expand Up @@ -85,7 +85,16 @@ bool splitGlobal(GlobalVariable &GV) {
uint64_t ByteOffset = cast<ConstantInt>(
cast<ConstantAsMetadata>(Type->getOperand(0))->getValue())
->getZExtValue();
if (ByteOffset < SplitBegin || ByteOffset >= SplitEnd)
// Type metadata may be attached one byte after the end of the vtable, for
// classes without virtual methods in Itanium ABI. AFAIK, it is never
// attached to the first byte of a vtable. Subtract one to get the right
// slice.
// This is making an assumption that vtable groups are the only kinds of
// global variables that !type metadata can be attached to, and that they
// are either Itanium ABI vtable groups or contain a single vtable (i.e.
// Microsoft ABI vtables).
uint64_t AttachedTo = (ByteOffset == 0) ? ByteOffset : ByteOffset - 1;
if (AttachedTo < SplitBegin || AttachedTo >= SplitEnd)
continue;
SplitGV->addMetadata(
LLVMContext::MD_type,
Expand Down
20 changes: 13 additions & 7 deletions llvm/test/Transforms/GlobalSplit/basic.ll
Expand Up @@ -12,13 +12,13 @@ target triple = "x86_64-unknown-linux-gnu"
]

; CHECK-NOT: @global =
; CHECK: @global.0 = private constant [2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2], !type [[T1:![0-9]+$]]
; CHECK: @global.1 = private constant [1 x i8* ()*] [i8* ()* @f3], !type [[T2:![0-9]+$]]
; CHECK: @global.0 = private constant [2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2], !type [[T1:![0-9]+]], !type [[T2:![0-9]+]], !type [[T3:![0-9]+$]]
; CHECK: @global.1 = private constant [1 x i8* ()*] [i8* ()* @f3], !type [[T4:![0-9]+]], !type [[T5:![0-9]+$]]
; CHECK-NOT: @global =
@global = internal constant { [2 x i8* ()*], [1 x i8* ()*] } {
[2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2],
[1 x i8* ()*] [i8* ()* @f3]
}, !type !0, !type !1
}, !type !0, !type !1, !type !2, !type !3, !type !4

; CHECK: define i8* @f1()
define i8* @f1() {
Expand Down Expand Up @@ -51,7 +51,13 @@ define void @foo() {

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

; CHECK: [[T1]] = !{i32 8, !"foo"}
; CHECK: [[T2]] = !{i32 0, !"bar"}
!0 = !{i32 8, !"foo"}
!1 = !{i32 16, !"bar"}
; CHECK: [[T1]] = !{i32 0, !"foo"}
; CHECK: [[T2]] = !{i32 15, !"bar"}
; CHECK: [[T3]] = !{i32 16, !"a"}
; CHECK: [[T4]] = !{i32 1, !"b"}
; CHECK: [[T5]] = !{i32 8, !"c"}
!0 = !{i32 0, !"foo"}
!1 = !{i32 15, !"bar"}
!2 = !{i32 16, !"a"}
!3 = !{i32 17, !"b"}
!4 = !{i32 24, !"c"}

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