emaste 930481b8f6 lld: [ELF][ARM] Implement support for Tag_ABI_VFP_args
The Tag_ABI_VFP_args build attribute controls the procedure call
standard used for floating point parameters on ARM. The values are:

0 - Base AAPCS (FP Parameters passed in Core (Integer) registers
1 - VFP AAPCS (FP Parameters passed in FP registers)
2 - Toolchain specific (Neither Base or VFP)
3 - Compatible with all (No use of floating point parameters)

If the Tag_ABI_VFP_args build attribute is missing it has an implicit
value of 0.

We use the attribute in two ways:

* Detect a clash in calling convention between Base, VFP and Toolchain.

we follow ld.bfd's lead and do not error if there is a clash between an
implicit Base AAPCS caused by a missing attribute. Many projects
including the hard-float (VFP AAPCS) version of glibc contain assembler
files that do not use floating point but do not have Tag_ABI_VFP_args.

* Set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD ELF header flag

for Base or VFP AAPCS respectively. This flag is used by some ELF
loaders.

References:
* Addenda to, and Errata in, the ABI for the ARM Architecture for
  Tag_ABI_VFP_args
* Elf for the ARM Architecture for ELF header flags

Fixes LLVM PR36009

PR:		229050
Obtained from:	llvm r338377 by Peter Smith
2018-07-31 15:25:03 +00:00
..

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.