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llvm-project/llvm/test/Bitcode/dso_location.ll

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Represent runtime preemption in the IR. Currently we do not represent runtime preemption in the IR, which has several drawbacks: 1) The semantics of GlobalValues differ depending on the object file format you are targeting (as well as the relocation-model and -fPIE value). 2) We have no way of disabling inlining of run time interposable functions, since in the IR we only know if a function is link-time interposable. Because of this llvm cannot support elf-interposition semantics. 3) In LTO builds of executables we will have extra knowledge that a symbol resolved to a local definition and can't be preemptable, but have no way to propagate that knowledge through the compiler. This patch adds preemptability specifiers to the IR with the following meaning: dso_local --> means the compiler may assume the symbol will resolve to a definition within the current linkage unit and the symbol may be accessed directly even if the definition is not within this compilation unit. dso_preemptable --> means that the compiler must assume the GlobalValue may be replaced with a definition from outside the current linkage unit at runtime. To ease transitioning dso_preemptable is treated as a 'default' in that low-level codegen will still do the same checks it did previously to see if a symbol should be accessed indirectly. Eventually when IR producers emit the specifiers on all Globalvalues we can change dso_preemptable to mean 'always access indirectly', and remove the current logic. Differential Revision: https://reviews.llvm.org/D20217 llvm-svn: 316668
2017-10-26 23:00:26 +08:00
; RUN: llvm-as < %s | llvm-dis | FileCheck %s
; Tests parsing for the dso_local keyword as well as the serialization/
; deserialization of the dso_local value on GlobalValues.
@local_global = dso_local global i32 0
; CHECK: @local_global = dso_local global i32 0
@weak_local_global = weak dso_local global i32 0
; CHECK: @weak_local_global = weak dso_local global i32 0
@external_local_global = external dso_local global i32
; CHECK: @external_local_global = external dso_local global i32
@default_local_global = dso_local default global i32 0
; CHECK: @default_local_global = dso_local global i32 0
@hidden_local_global = dso_local hidden global i32 0
; CHECK: @hidden_local_global = dso_local hidden global i32 0
@protected_local_global = dso_local protected global i32 0
; CHECK: @protected_local_global = dso_local protected global i32 0
@local_alias = dso_local alias i32, i32* @local_global
; CHECK-DAG: @local_alias = dso_local alias i32, i32* @local_global
@preemptable_alias = dso_preemptable alias i32, i32* @hidden_local_global
; CHECK-DAG: @preemptable_alias = alias i32, i32* @hidden_local_global
@preemptable_ifunc = dso_preemptable ifunc void (), i8* ()* @ifunc_resolver
; CHECK-DAG: @preemptable_ifunc = ifunc void (), i8* ()* @ifunc_resolver
declare dso_local default void @default_local()
; CHECK: declare dso_local void @default_local()
declare dso_local hidden void @hidden_local()
; CHECK: declare dso_local hidden void @hidden_local()
define dso_local protected void @protected_local() {
; CHECK: define dso_local protected void @protected_local()
entry:
ret void
}
define i8* @ifunc_resolver() {
entry:
ret i8* null
}