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llvm-mirror/test/ThinLTO/X86/index-const-prop-dead.ll
Fangrui Song d41ca54775 [ThinLTO] Drop dso_local if a GlobalVariable satisfies isDeclarationForLinker()
dso_local leads to direct access even if the definition is not within this compilation unit (it is
still in the same linkage unit). On ELF, such a relocation (e.g. R_X86_64_PC32) referencing a
STB_GLOBAL STV_DEFAULT object can cause a linker error in a -shared link.

If the linkage is changed to available_externally, the dso_local flag should be dropped, so that no
direct access will be generated.

The current behavior is benign, because -fpic does not assume dso_local
(clang/lib/CodeGen/CodeGenModule.cpp:shouldAssumeDSOLocal).
If we do that for -fno-semantic-interposition (D73865), there will be an
R_X86_64_PC32 linker error without this patch.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D74751
2020-04-07 15:46:01 -07:00

27 lines
879 B
LLVM

; RUN: opt -module-summary %s -o %t1.bc
; RUN: opt -module-summary %p/Inputs/index-const-prop-define-g.ll -o %t2.bc
; RUN: llvm-lto2 run -save-temps %t2.bc -r=%t2.bc,g,pl \
; RUN: %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,foo,pl -r=%t1.bc,g, -o %t3
; RUN: llvm-dis %t3.2.3.import.bc -o - | FileCheck %s
; Dead globals are converted to declarations by ThinLTO in dropDeadSymbols
; If we try to internalize such we'll get a broken module.
; CHECK: @g = external global i32
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-unknown-linux-gnu"
@g = external global i32
; We need at least one live symbol to enable dead stripping
; Otherwise ModuleSummaryIndex::isGlobalValueLive will always
; return true.
define i32 @main() {
ret i32 42
}
define i32 @foo() {
%v = load i32, i32* @g
ret i32 %v
}