Thanks for your opinion! I did these just because LLVM has already done the
same thing and I wanted to make GCC with the same behavior of LLVM. The only
difference is that LLVM has no handling for ilp32f and lp64f and I have sent a
patch to do it (sees https://reviews.llvm.org/D125947).
As for RISC-V specs, there are some descriptions in
https://github.com/riscv-non-isa/riscv-toolchain-conventions#specifying-the-target-isa-with--march:
> A target -march which includes floating point instructions implies a
> hardfloat calling convention, but can be overridden using the -mabi flag (see
> the next section).
But I think we can make it clearer.
------------------------------------------------------------------
Sender:Palmer Dabbelt <pal...@dabbelt.com>
Sent At:2022 Jun. 8 (Wed.) 02:45
Recipient:gcc-patches <gcc-patches@gcc.gnu.org>
Cc:pc.wang <pc.w...@linux.alibaba.com>
Subject:Re: [PATCH] RISC-V: Compute default ABI from -mcpu or -march
On Mon, 06 Jun 2022 19:51:20 PDT (-0700), gcc-patches@gcc.gnu.org wrote:
> If -mcpu or -march is specified and there is no -mabi, we will calculate
> default ABI from arch string provided by -march or defined in CPU info.
IMO this is generally a good idea and we've talked about it before, but
just setting the ABI from the ISA isn't quite the right way to go. IIRC
we came up with something slightly more complicated, like picking the
closest supported multilib. That's probably more in line with what
users are asking for, which IIUC is sort of just "I don't care that much
about ABI, just make my stuff build".
Whatever we do here, we should document in the RISC-V specs as we'll
want to make sure LLVM does the same thing. We probably also want some
sort of "-mabi=auto" argument, as it's always best to have an argument
that changes back to the no-argument behavior.
>
> gcc/ChangeLog:
>
> * common/config/riscv/riscv-common.cc (compute_default_abi):
> Implementation
> to calculate -mabi from arch string.
> (riscv_expand_abi_from_arch): New spec function to calcalute -mabi
> from arch
> string provided by -march option.
> (riscv_expand_abi_from_cpu): New spec function to find CPU info and
> calculate
> -mabi from arch string defined in CPU info.
> * config/riscv/riscv.h (EXTRA_SPEC_FUNCTIONS): Add above spec
> functions.
> (OPTION_DEFAULT_SPECS): Use new spec functions to calculate -mabi and
> -march
> has higher priority than -mcpu.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/mabi-1.c: ilp32e test.
> * gcc.target/riscv/mabi-2.c: ilp32 test.
> * gcc.target/riscv/mabi-3.c: ilp32f test.
> * gcc.target/riscv/mabi-4.c: ilp32d test.
> * gcc.target/riscv/mabi-5.c: lp64 test.
> * gcc.target/riscv/mabi-6.c: lp64f test.
> * gcc.target/riscv/mabi-7.c: lp64d test.
> * gcc.target/riscv/mabi-8.c: -march override -mcpu.
> ---
> gcc/common/config/riscv/riscv-common.cc | 66 +++++++++++++++++++++++++
> gcc/config/riscv/riscv.h | 15 ++++--
> gcc/testsuite/gcc.target/riscv/mabi-1.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-2.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-3.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-4.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-5.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-6.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-7.c | 7 +++
> gcc/testsuite/gcc.target/riscv/mabi-8.c | 7 +++
> 10 files changed, 134 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-1.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-2.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-3.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-4.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-5.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-6.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-7.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/mabi-8.c
>
> diff --git a/gcc/common/config/riscv/riscv-common.cc
> b/gcc/common/config/riscv/riscv-common.cc
> index 0e5be2ce105..f8e40549d18 100644
> --- a/gcc/common/config/riscv/riscv-common.cc
> +++ b/gcc/common/config/riscv/riscv-common.cc
> @@ -1266,6 +1266,72 @@ riscv_default_mtune (int argc, const char **argv)
> return default_mtune;
> }
>
> +/* Compute default -mabi option from arch string. */
> +
> +static const char *
> +compute_default_abi (const char* arch_str)
> +{
> + location_t loc = UNKNOWN_LOCATION;
> +
> + riscv_parse_arch_string (arch_str, NULL, loc);
> +
> + if (current_subset_list->xlen () == 64)
> + {
> + if (current_subset_list->lookup ("d", RISCV_DONT_CARE_VERSION,
> + RISCV_DONT_CARE_VERSION))
> + return "lp64d";
> + if (current_subset_list->lookup ("f", RISCV_DONT_CARE_VERSION,
> + RISCV_DONT_CARE_VERSION))
> + return "lp64f";
> + return "lp64";
> + }
> + else
> + {
> + if (current_subset_list->lookup ("e", RISCV_DONT_CARE_VERSION,
> + RISCV_DONT_CARE_VERSION))
> + return "ilp32e";
> + if (current_subset_list->lookup ("d", RISCV_DONT_CARE_VERSION,
> + RISCV_DONT_CARE_VERSION))
> + return "ilp32d";
> + if (current_subset_list->lookup ("f", RISCV_DONT_CARE_VERSION,
> + RISCV_DONT_CARE_VERSION))
> + return "ilp32f";
> + return "ilp32";
> + }
> +}
> +
> +/* Expand default -mabi option from -march option. */
> +
> +const char *
> +riscv_expand_abi_from_arch (int argc, const char **argv)
> +{
> + gcc_assert (argc == 1);
> + return xasprintf ("-mabi=%s", compute_default_abi (argv[0]));
> +}
> +
> +/* Expand default -mabi option from -mcpu option. */
> +
> +const char *
> +riscv_expand_abi_from_cpu (int argc, const char **argv)
> +{
> + gcc_assert (argc > 0 && argc <= 2);
> + const char *default_abi_str = NULL;
> + if (argc >= 2)
> + default_abi_str = argv[1];
> +
> + const riscv_cpu_info *cpu = riscv_find_cpu (argv[0]);
> +
> + if (cpu == NULL)
> + {
> + if (default_abi_str == NULL)
> + return "";
> + else
> + return xasprintf ("-mabi=%s", default_abi_str);
> + }
> + else
> + return xasprintf ("-mabi=%s", compute_default_abi (cpu->arch));
> +}
> +
> /* Expand arch string with implied extensions from -mcpu option. */
>
> const char *
> diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h
> index 6f7f4d3fbdc..14cd695f37f 100644
> --- a/gcc/config/riscv/riscv.h
> +++ b/gcc/config/riscv/riscv.h
> @@ -50,15 +50,20 @@ along with GCC; see the file COPYING3. If not see
> extern const char *riscv_expand_arch (int argc, const char **argv);
> extern const char *riscv_expand_arch_from_cpu (int argc, const char **argv);
> extern const char *riscv_default_mtune (int argc, const char **argv);
> +extern const char *riscv_expand_abi_from_arch (int argc, const char **argv);
> +extern const char *riscv_expand_abi_from_cpu (int argc, const char **argv);
>
> # define EXTRA_SPEC_FUNCTIONS \
> { "riscv_expand_arch", riscv_expand_arch }, \
> { "riscv_expand_arch_from_cpu", riscv_expand_arch_from_cpu }, \
> - { "riscv_default_mtune", riscv_default_mtune },
> + { "riscv_default_mtune", riscv_default_mtune }, \
> + { "riscv_expand_abi_from_arch", riscv_expand_abi_from_arch }, \
> + { "riscv_expand_abi_from_cpu", riscv_expand_abi_from_cpu },
>
> /* Support for a compile-time default CPU, et cetera. The rules are:
> --with-arch is ignored if -march or -mcpu is specified.
> - --with-abi is ignored if -mabi is specified.
> + --with-abi is ignored if -mabi is specified. If -mcpu or -march is
> + specified, suitable -mabi will be selected from arch string.
> --with-tune is ignored if -mtune or -mcpu is specified.
> --with-isa-spec is ignored if -misa-spec is specified.
>
> @@ -70,7 +75,11 @@ extern const char *riscv_default_mtune (int argc, const
> char **argv);
> {"arch", "%{!march=*:" \
> " %{!mcpu=*:-march=%(VALUE)}" \
> " %{mcpu=*:%:riscv_expand_arch_from_cpu(%* %(VALUE))}}" }, \
> - {"abi", "%{!mabi=*:-mabi=%(VALUE)}" }, \
> + {"abi", "%{!mabi=*:" \
> + " %{!march=*:" \
> + " %{!mcpu=*:-mabi=%(VALUE)}" \
> + " %{mcpu=*:%:riscv_expand_abi_from_cpu(%* %(VALUE))}}" \
> + " %{march=*:%:riscv_expand_abi_from_arch(%*)}}" }, \
> {"isa_spec", "%{!misa-spec=*:-misa-spec=%(VALUE)}" }, \
>
> #ifdef IN_LIBGCC2
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-1.c
> b/gcc/testsuite/gcc.target/riscv/mabi-1.c
> new file mode 100644
> index 00000000000..83bc343f8d8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-1.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv32e" } */
> +
> +#if !((__riscv_xlen == 32) && defined(__riscv_abi_rve))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-2.c
> b/gcc/testsuite/gcc.target/riscv/mabi-2.c
> new file mode 100644
> index 00000000000..6a97c2ae2a3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-2.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv32ima" } */
> +
> +#if !((__riscv_xlen == 32) && defined(__riscv_float_abi_soft))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-3.c
> b/gcc/testsuite/gcc.target/riscv/mabi-3.c
> new file mode 100644
> index 00000000000..cef04313e19
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-3.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv32imaf" } */
> +
> +#if !((__riscv_xlen == 32) && defined(__riscv_float_abi_single))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-4.c
> b/gcc/testsuite/gcc.target/riscv/mabi-4.c
> new file mode 100644
> index 00000000000..d62dcf6ed75
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-4.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv32imafd" } */
> +
> +#if !((__riscv_xlen == 32) && defined(__riscv_float_abi_double))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-5.c
> b/gcc/testsuite/gcc.target/riscv/mabi-5.c
> new file mode 100644
> index 00000000000..000e5e282c2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-5.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv64ima" } */
> +
> +#if !((__riscv_xlen == 64) && defined(__riscv_float_abi_soft))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-6.c
> b/gcc/testsuite/gcc.target/riscv/mabi-6.c
> new file mode 100644
> index 00000000000..ed1458d4158
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-6.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv64imaf" } */
> +
> +#if !((__riscv_xlen == 64) && defined(__riscv_float_abi_single))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-7.c
> b/gcc/testsuite/gcc.target/riscv/mabi-7.c
> new file mode 100644
> index 00000000000..675fe359cfd
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-7.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-march=rv64imafd" } */
> +
> +#if !((__riscv_xlen == 64) && defined(__riscv_float_abi_double))
> +#error "unexpected abi"
> +#endif
> diff --git a/gcc/testsuite/gcc.target/riscv/mabi-8.c
> b/gcc/testsuite/gcc.target/riscv/mabi-8.c
> new file mode 100644
> index 00000000000..8c7e08e4289
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mabi-8.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "-mabi given" { *-*-* } { "-mabi=*" } } */
> +/* { dg-options "-mcpu=sifive-s21 -march=rv64imafd" } */
> +
> +#if !((__riscv_xlen == 64) && defined(__riscv_float_abi_double))
> +#error "unexpected abi"
> +#endif
