On 05/08/2022 14:53, Richard Sandiford via Gcc-patches wrote:
Richard Earnshaw <richard.earns...@foss.arm.com> writes:
On 13/06/2022 15:33, Richard Sandiford via Gcc-patches wrote:
On aarch64, --with-arch, --with-cpu and --with-tune only have an
effect on the driver, so “./xgcc -B./ -O3” can give significantly
different results from “./cc1 -O3”. --with-arch did have a limited
effect on ./cc1 in previous releases, although it didn't work
entirely correctly.
Being of a lazy persuasion, I've got used to ./cc1 selecting SVE for
--with-arch=armv8.2-a+sve without having to supply an explicit -march,
so this patch makes ./cc1 emulate the relevant OPTION_DEFAULT_SPECS.
It relies on Wilco's earlier clean-ups.
The patch makes config.gcc define WITH_FOO_STRING macros for each
supported --with-foo option. This could be done only in aarch64-
specific code, but I thought it could be useful on other targets
too (and can be safely ignored otherwise). There didn't seem to
be any existing and potentially clashing uses of macros with this
style of name.
Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK for the configure
bits?
Richard
gcc/
* config.gcc: Define WITH_FOO_STRING macros for each supported
--with-foo option.
* config/aarch64/aarch64.cc (aarch64_override_options): Emulate
OPTION_DEFAULT_SPECS.
* config/aarch64/aarch64.h (OPTION_DEFAULT_SPECS): Reference the above.
---
gcc/config.gcc | 14 ++++++++++++++
gcc/config/aarch64/aarch64.cc | 8 ++++++++
gcc/config/aarch64/aarch64.h | 5 ++++-
3 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index cdbefb5b4f5..e039230431c 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -5865,6 +5865,20 @@ else
configure_default_options="{ ${t} }"
fi
+for option in $supported_defaults
+do
+ lc_option=`echo $option | sed s/-/_/g`
+ uc_option=`echo $lc_option | tr a-z A-Z`
+ eval "val=\$with_$lc_option"
+ if test -n "$val"
+ then
+ val="\\\"$val\\\""
+ else
+ val=nullptr
+ fi
+ tm_defines="$tm_defines WITH_${uc_option}_STRING=$val"
+done
This bit would really be best reviewed by a non-arm maintainer. It
generally looks OK. My only comment would be why define anything if the
corresponding --with-foo was not specified. They you can use #ifdef to
test if the user specified a default.
Yeah, could do it that way instead, but:
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index d21e041eccb..0bc700b81ad 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -18109,6 +18109,14 @@ aarch64_override_options (void)
if (aarch64_branch_protection_string)
aarch64_validate_mbranch_protection (aarch64_branch_protection_string);
+ /* Emulate OPTION_DEFAULT_SPECS. */
+ if (!aarch64_arch_string && !aarch64_cpu_string)
+ aarch64_arch_string = WITH_ARCH_STRING;
+ if (!aarch64_arch_string && !aarch64_cpu_string)
+ aarch64_cpu_string = WITH_CPU_STRING;
+ if (!aarch64_cpu_string && !aarch64_tune_string)
+ aarch64_tune_string = WITH_TUNE_STRING;
(without the preprocessor stuff) IMO reads better. If a preprocessor
is/isn't present test turns out to be useful, perhaps we should add
macros like HAVE_WITH_TUNE/WITH_TUNE_PRESENT/... too? I guess it
should only be done when something needs it though.
It's relatively easy to add
#ifndef WITH_TUNE_STRING
#define WITH_TUNE_STRING (nulptr)
#endif
in a header, but much harder to go the other way. The case I was
thinking of was something like:
#if !defined(WITH_ARCH_STRING) && !defined(WITH_CPU_STRING)
#define WITH_ARCH_STRING "<some-target-default>"
#endif
which saves having to have yet another level of fallback if nothing has
been specified, but this is next to impossible if the macros are
unconditionally defined.
R.
Thanks,
Richard
+
/* -mcpu=CPU is shorthand for -march=ARCH_FOR_CPU, -mtune=CPU.
If either of -march or -mtune is given, they override their
respective component of -mcpu. */
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 80cfe4b7407..3122dbd7098 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -1267,7 +1267,10 @@ extern enum aarch64_code_model aarch64_cmodel;
/* Support for configure-time --with-arch, --with-cpu and --with-tune.
--with-arch and --with-cpu are ignored if either -mcpu or -march is used.
--with-tune is ignored if either -mtune or -mcpu is used (but is not
- affected by -march). */
+ affected by -march).
+
+ There is corresponding code in aarch64_override_options that emulates
+ this behavior when cc1 &co are invoked directly. */
#define OPTION_DEFAULT_SPECS \
{"arch", "%{!march=*:%{!mcpu=*:-march=%(VALUE)}}" }, \
{"cpu", "%{!march=*:%{!mcpu=*:-mcpu=%(VALUE)}}" }, \
