The documentation for the "-mabi" argument on RISC-V was incorrect. We chose to treat this as a documentation bug rather than a code bug, and to make the documentation match what GCC currently does. In the process, I also improved the documentation a bit.
Thanks to Alex Bradbury for finding the bug! PR target/82717: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82717 gcc/ChangeLog 2017-10-26 Palmer Dabbelt <pal...@dabbelt.com> PR target/82717 * doc/invoke.texi (RISC-V) <-mabi>: Correct and improve. --- gcc/doc/invoke.texi | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 71b2445f70fd..d184e1d7b7d4 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -21669,9 +21669,26 @@ When generating PIC code, allow the use of PLTs. Ignored for non-PIC. @item -mabi=@var{ABI-string} @opindex mabi -Specify integer and floating-point calling convention. This defaults to the -natural calling convention: e.g.@ LP64 for RV64I, ILP32 for RV32I, LP64D for -RV64G. +@item -mabi=@var{ABI-string} +@opindex mabi +Specify integer and floating-point calling convention. @var{ABI-string} +contains two parts: the size of integer types and the registers used for +floating-point types. For example @samp{-march=rv64ifd -mabi=lp64d} means that +@samp{long} and pointers are 64-bit (implicitly defining @samp{int} to be +32-bit), and that floating-point values up to 64 bits wide are passed in F +registers. Contrast this with @samp{-march=rv64ifd -mabi=lp64f}, which still +allows the compiler to generate code that uses the F and D extensions but only +allows floating-point values up to 32 bits long to be passed in registers; or +@samp{-march=rv64ifd -mabi=lp64}, in which no floating-point arguments will be +passed in registers. + +The default for this argument is system dependent, users who want a specific +calling convention should specify one explicitly. The valid calling +conventions are: @samp{ilp32}, @samp{ilp32f}, @samp{ilp32d}, @samp{lp64}, +@samp{lp64f}, and @samp{lp64d}. Some calling conventions are impossible to +implement on some ISAs: for example, @samp{-march=rv32if -mabi=ilp32d} is +invalid because the ABI requires 64-bit values be passed in F registers, but F +registers are only 32 bits wide. @item -mfdiv @itemx -mno-fdiv -- 2.13.6
