Summary:
L is meant to support the second word used by 32b calling conventions for 64b arguments.
This is required for build 32b PowerPC Linux kernels after upstream
commit 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'")
Thanks for the report from @nathanchance, and reference to GCC's
implementation from @segher.
Fixes: pr/46186
Fixes: https://github.com/ClangBuiltLinux/linux/issues/1044
Reviewers: echristo, hfinkel, MaskRay
Reviewed By: MaskRay
Subscribers: MaskRay, wuzish, nemanjai, hiraditya, kbarton, steven.zhang, llvm-commits, segher, nathanchance, srhines
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D81767
89b7fb0173