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Linker: Avoid scheduling the link of a global value twice due to an alias

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3d4f3a0da90bd1a3 (https://reviews.llvm.org/D20586) avoided rescheduling
a global value that was materialized first through a regular value, and
then again through an alias. This commit catches the dual, avoiding
rescheduling when the global value is first materialized through an
alias.

Differential Revision: https://reviews.llvm.org/D101419
Radar-Id: rdar://75752728
This commit is contained in:
Duncan P. N. Exon Smith 2021-04-27 18:02:22 -07:00
parent f9ae80f6b1
commit fdb0c0cbf7
2 changed files with 20 additions and 7 deletions
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15
lib/Linker/IRMover.cpp
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@ -610,15 +610,16 @@ Value *IRLinker::materialize(Value *V, bool ForIndirectSymbol) {
return New;
}
// When linking a global for an indirect symbol, it will always be linked.
// However we need to check if it was not already scheduled to satisfy a
// reference from a regular global value initializer. We know if it has been
// schedule if the "New" GlobalValue that is mapped here for the indirect
// symbol is the same as the one already mapped. If there is an entry in the
// If the global is being linked for an indirect symbol, it may have already
// been scheduled to satisfy a regular symbol. Similarly, a global being linked
// for a regular symbol may have already been scheduled for an indirect
// symbol. Check for these cases by looking in the other value map and
// confirming the same value has been scheduled. If there is an entry in the
// ValueMap but the value is different, it means that the value already had a
// definition in the destination module (linkonce for instance), but we need a
// new definition for the indirect symbol ("New" will be different.
if (ForIndirectSymbol && ValueMap.lookup(SGV) == New)
// new definition for the indirect symbol ("New" will be different).
if ((ForIndirectSymbol && ValueMap.lookup(SGV) == New) ||
(!ForIndirectSymbol && IndirectSymbolValueMap.lookup(SGV) == New))
return New;
if (ForIndirectSymbol || shouldLink(New, *SGV))

12
test/Linker/alias-4.ll Normal file
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@ -0,0 +1,12 @@
; RUN: llvm-link %s -S -o - | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.9"
; CHECK-DAG: @gv0 = constant i64* @alias
; CHECK-DAG: @gv1 = constant i64 ptrtoint (i64* @gv1 to i64)
; CHECK-DAG: @alias = alias i64, i64* @gv1
@gv0 = constant i64* @alias
@gv1 = constant i64 ptrtoint (i64* @gv1 to i64)
@alias = alias i64, i64* @gv1