[PATCH] D101419: Linker: Avoid scheduling the link of a global value twice due to an alias
Duncan P. N. Exon Smith via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 27 18:14:00 PDT 2021
dexonsmith created this revision.
dexonsmith added reviewers: mehdi_amini, steven_wu.
Herald added a subscriber: hiraditya.
dexonsmith requested review of this revision.
Herald added a project: LLVM.
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.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D101419
Files:
llvm/lib/Linker/IRMover.cpp
llvm/test/Linker/alias-4.ll
Index: llvm/test/Linker/alias-4.ll
===================================================================
--- /dev/null
+++ llvm/test/Linker/alias-4.ll
@@ -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
+
+ at gv0 = constant i64* @alias
+ at gv1 = constant i64 ptrtoint (i64* @gv1 to i64)
+
+ at alias = alias i64, i64* @gv1
Index: llvm/lib/Linker/IRMover.cpp
===================================================================
--- llvm/lib/Linker/IRMover.cpp
+++ llvm/lib/Linker/IRMover.cpp
@@ -610,15 +610,16 @@
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))
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