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llvm-mirror/test/ThinLTO/X86/index-const-prop-alias.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

43 lines
1.8 KiB
LLVM

; RUN: opt -module-summary %s -o %t1.bc
; RUN: opt -module-summary %p/Inputs/index-const-prop-alias.ll -o %t2.bc
; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,pl -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,pl -save-temps -o %t3
; RUN: llvm-dis %t3.1.3.import.bc -o - | FileCheck %s --check-prefix=IMPORT
; RUN: llvm-dis %t3.1.5.precodegen.bc -o - | FileCheck %s --check-prefix=CODEGEN
; When ret_ptr is preserved we return pointer to alias, so we can't internalize aliasee
; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,plx -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,pl -save-temps -o %t4
; RUN: llvm-dis %t4.1.3.import.bc -o - | FileCheck %s --check-prefix=PRESERVED
; When g.alias is preserved we can't internalize aliasee either
; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,pl -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,plx -save-temps -o %t5
; RUN: llvm-dis %t5.1.3.import.bc -o - | FileCheck %s --check-prefix=PRESERVED
; We currently don't support importing aliases
; IMPORT: @g.alias = external global i32
; IMPORT-NEXT: @g = internal global i32 42, align 4 #0
; IMPORT: attributes #0 = { "thinlto-internalize" }
; CODEGEN: define dso_local i32 @main
; CODEGEN-NEXT: ret i32 42
; PRESERVED: @g.alias = external global i32
; PRESERVED-NEXT: @g = available_externally global i32 42, align 4
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.alias = external global i32
@g = external global i32
define i32 @main() {
%v = load i32, i32* @g
ret i32 %v
}
define i32* @ret_ptr() {
ret i32* @g.alias
}