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[clang][driver] Pass -femulated-tls through to the linker in LTO mode

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Currently the driver does not propagate the `-f[no-]emulated-tls` flags
to the linker under LTO. This can be surprising when the platform
defaults differ from the flags being passed. A related discussion can be
found in https://reviews.llvm.org/D143619. While the focus there was
RISC-V support, the root cause was that setting `-femualted-tls` and
`-flto` when compiling with Clang resulted in missing symbols because
the platform defaults for Android differed from the flags being passed
to Clang.

This patch changes the Clang driver's behavior to pass the emulated-tls
flags through to the linker when compiling with LTO/ThinLTO.

Reviewed By: phosek, vit9696

Differential Revision: https://reviews.llvm.org/D147834
This commit is contained in:
Paul Kirth 2023-02-13 18:18:33 +00:00
parent eb65912e41
commit a78816a6b6
2 changed files with 24 additions and 0 deletions
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7
clang/lib/Driver/ToolChains/CommonArgs.cpp
View File

@ -764,6 +764,13 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
D.Diag(clang::diag::warn_drv_fjmc_for_elf_only);
}
if (Arg *A = Args.getLastArg(options::OPT_femulated_tls,
options::OPT_fno_emulated_tls)) {
bool Enable = A->getOption().getID() == options::OPT_femulated_tls;
CmdArgs.push_back(Args.MakeArgString(
Twine(PluginOptPrefix) + "-emulated-tls=" + (Enable ? "1" : "0")));
}
if (Args.hasFlag(options::OPT_fstack_size_section,
options::OPT_fno_stack_size_section, false))
CmdArgs.push_back(

17
clang/test/Driver/emulated-tls.cpp
View File

@ -29,6 +29,16 @@
// RUN: %clang -### -target i686-pc-openbsd %s -femulated-tls -fno-emulated-tls 2>&1 \
// RUN: | FileCheck -check-prefix=NOEMU %s
// Test that when lto is used any -emualted-tls flags are passed to the linker
// LINUX and Android have different defaults for EmulatedTLS
// RUN: %clang -### -flto --target=riscv64-linux -fno-emulated-tls %s 2>&1 \
// RUN: | FileCheck %s --check-prefix=LTO_NOEMUTLS
// RUN: %clang -### -flto --target=riscv64-linux-android10000 -femulated-tls %s 2>&1 \
// RUN: | FileCheck %s --check-prefix=LTO_EMUTLS
// RUN: %clang -### -flto --target=riscv64-linux -femulated-tls %s 2>&1 \
// RUN: | FileCheck %s --check-prefix=LTO_EMUTLS
// RUN: %clang -### -flto --target=riscv64-linux-android10000 -fno-emulated-tls %s 2>&1 \
// RUN: | FileCheck %s --check-prefix=LTO_NOEMUTLS
// Default without -f[no-]emulated-tls, will be decided by the target triple.
// DEFAULT-NOT: "-cc1" {{.*}}"-femulated-tls"
@ -40,3 +50,10 @@
// NOEMU: "-cc1" {{.*}}"-fno-emulated-tls"
// NOEMU-NOT: "-cc1" {{.*}}"-femulated-tls"
// LTO related checks
// LTO_NOEMUTLS: plugin-opt=-emulated-tls=0
// LTO_NOEMUTLS-NOT: plugin-opt=-emulated-tls=1
// LTO_EMUTLS: plugin-opt=-emulated-tls=1
// LTO_EMUTLS-NOT: plugin-opt=-emulated-tls=0