[ELF] Add convenience TableGen classes to enforce two dashes for options not supported by GNU ld

Announced on https://lists.llvm.org/pipermail/llvm-dev/2020-May/141416.html

For many options, we hav

[ELF] Add convenience TableGen classes to enforce two dashes for options not supported by GNU ld

Announced on https://lists.llvm.org/pipermail/llvm-dev/2020-May/141416.html

For many options, we have to support either one or two dash to be
compatible with GNU ld. For newer and lld specific options, we can enforce strict double dashes.

Affected options:

* --thinlto-*
* --lto-*
* --shuffle-sections=

This patch does not change `-plugin-opt=*` because clang driver passes
`-plugin-opt=*` and I don't intend to cause churn.

In 2000, GNU ld tried something similar with --omagic
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=e4897a3288f37d5f69e8acd256a6e83e607fe8d8

Reviewed By: tejohnson, psmith

Differential Revision: https://reviews.llvm.org/D79371

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[LTO] Suppress emission of empty combined module by default

Summary:
That unless the user requested an output object (--lto-obj-path), the an
unused empty combined module is not emitted.

This chang

[LTO] Suppress emission of empty combined module by default

Summary:
That unless the user requested an output object (--lto-obj-path), the an
unused empty combined module is not emitted.

This changed is helpful for some target (ex. RISCV-V) which encoded the
ABI info in IR module flags (target-abi). Empty unused module has no ABI
info so the linker would get the linking error during merging
incompatible ABIs.

Reviewers: tejohnson, espindola, MaskRay

Subscribers: emaste, inglorion, arichardson, hiraditya, simoncook, MaskRay, steven_wu, dexonsmith, PkmX, dang, lenary, s.egerton, luismarques, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78988

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[Object] Change ELFObjectFile<ELFT>::getFileFormatName() to use BFD names

Follow-up for D74433

What the function returns are almost standard BFD names, except that "ELF" is
in uppercase instead of

[Object] Change ELFObjectFile<ELFT>::getFileFormatName() to use BFD names

Follow-up for D74433

What the function returns are almost standard BFD names, except that "ELF" is
in uppercase instead of lowercase.

This patch changes "ELF" to "elf" and changes ARM/AArch64 to use their BFD names.
MIPS and PPC64 have endianness differences as well, but this patch does not intend to address them.

Advantages:

* llvm-objdump: the "file format " line matches GNU objdump on ARM/AArch64 objects
* "file format " line can be extracted and fed into llvm-objcopy -O literally.
(https://github.com/ClangBuiltLinux/linux/issues/779 has such a use case)

Affected tools: llvm-readobj, llvm-objdump, llvm-dwarfdump, MCJIT (internal implementation detail, not exposed)

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D76046

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[test] Fix test/ELF/lto/thinlto-obj-path.ll after D52810

[ELF] accept thinlto options without --plugin-opt= prefix

Summary:
When support for ThinLTO was first added to lld, the options that
control it were prefixed with --plugin-opt= for compatibility wit

[ELF] accept thinlto options without --plugin-opt= prefix

Summary:
When support for ThinLTO was first added to lld, the options that
control it were prefixed with --plugin-opt= for compatibility with
an existing implementation as a linker plugin. This change enables
shorter versions of the options to be used, as follows:

New Existing
-thinlto-emit-imports-files --plugin-opt=thinlto-emit-imports-files
-thinlto-index-only --plugin-opt=thinlto-index-only
-thinlto-index-only= --plugin-opt=thinlto-index-only=
-thinlto-object-suffix-replace= --plugin-opt=thinlto-object-suffix-replace=
-thinlto-prefix-replace= --plugin-opt=thinlto-prefix-replace=
-lto-obj-path= --plugin-opt=obj-path=

The options with the --plugin-opt= prefix have been retained as aliases
for the shorter variants so that they continue to be accepted.

Reviewers: tejohnson, ruiu, espindola

Reviewed By: ruiu

Subscribers: emaste, arichardson, MaskRay, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67782

llvm-svn: 372798

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Reland "Change the X86 datalayout to add three address spaces
for 32 bit signed, 32 bit unsigned, and 64 bit pointers."
This reverts 57076d3199fc2b0af4a3736b7749dd5462cacda5.

Original review at htt

Reland "Change the X86 datalayout to add three address spaces
for 32 bit signed, 32 bit unsigned, and 64 bit pointers."
This reverts 57076d3199fc2b0af4a3736b7749dd5462cacda5.

Original review at https://reviews.llvm.org/D64931.
Review for added fix at https://reviews.llvm.org/D66843.

llvm-svn: 371568

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Revert "Change the X86 datalayout to add three address spaces for 32 bit signed,"

This reverts commit r370083 because it caused check-lld failures on
sanitizer-x86_64-linux-fast.

llvm-svn: 370142

Change the X86 datalayout to add three address spaces for 32 bit signed,
32 bit unsigned, and 64 bit pointers.

llvm-svn: 370083

[llvm-nm] Write "no symbol" output to stderr

This matches the output of binutils' nm and ensures that any scripts
or tools that use nm and expect empty output in case there no symbols
don't break.

[llvm-nm] Write "no symbol" output to stderr

This matches the output of binutils' nm and ensures that any scripts
or tools that use nm and expect empty output in case there no symbols
don't break.

Differential Revision: https://reviews.llvm.org/D52943

llvm-svn: 343887

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[llvm-nm] Update lld tests based on changed llvm-nm output

llvm-svn: 343743

Splitting thinlto.ll test file and renaming other test files.

Differential Revision: https://reviews.llvm.org/D46731

llvm-svn: 332128