Summary:
Because GCC doesn't use $1 for code generation, inline assembly code can use $1 without having to add it to the clobbers list.
LLVM, on the other hand, does not shy away from using $1, and this can cause conflicts with inline assembly which assumes GCC-like code generation.
A solution to this problem is to make Clang automatically clobber $1 for all MIPS inline assembly.
This is not the optimal solution, but it seems like a necessary compromise, for now.
Reviewers: dsanders
Reviewed By: dsanders
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D6638
llvm-svn: 224428
Like GCC, this re-uses the 'f' constraint and a new 'w' print-modifier:
asm ("ldi.w %w0, 1", "=f"(result));
Unlike GCC, the 'w' print-modifer is not _required_ to produce the intended
output. This is a consequence of differences in the internal handling of
the registers in each compiler. To be source-compatible between the
compilers, users must use the 'w' print-modifier.
MSA registers (including control registers) are supported in clobber lists.
llvm-svn: 194476
David Blaikie