[PATCH 2/2] RISC-V: Implement TARGET_COMPUTE_MULTILIB
Kito Cheng
kito.cheng@sifive.com
Tue Dec 1 09:29:20 GMT 2020
Use TARGET_COMPUTE_MULTILIB to search the multi-lib reuse for riscv*-*-elf*,
according following rules:
1. Check ABI is same.
2. Check both has atomic extension or both don't have atomic extension.
- Because mix soft and hard atomic operation doesn't make sense and
won't work as expect.
3. Check current arch is superset of the target multi-lib arch.
- It might result slower performance or larger code size, but it
safe to run.
4. Pick most match multi-lib set if more than one multi-lib are pass
the above checking.
Example for how to select multi-lib:
We build code with -march=rv32imaf and -mabi=ilp32, and we have
following 5 multi-lib set:
1. rv32ia/ilp32
2. rv32ima/ilp32
3. rv32imf/ilp32
4. rv32imaf/ilp32f
5. rv32imafd/ilp32
The first and second multi-lib is safe to like, 3rd multi-lib can't
re-use becasue it don't have atomic extension, which is mismatch according
rule 2, and the 4th multi-lib can't re-use too due to the ABI mismatch,
the last multi-lib can't use since current arch is not superset of the
arch of multi-lib.
And emit error if not found suitable multi-lib set, the error message
only emit when link with standard libraries.
Example for when error will be emitted:
$ riscv64-unknown-elf-gcc -print-multi-lib
.;
rv32i/ilp32;@march=rv32i@mabi=ilp32
rv32im/ilp32;@march=rv32im@mabi=ilp32
rv32iac/ilp32;@march=rv32iac@mabi=ilp32
rv32imac/ilp32;@march=rv32imac@mabi=ilp32
rv32imafc/ilp32f;@march=rv32imafc@mabi=ilp32f
rv64imac/lp64;@march=rv64imac@mabi=lp64
// No actual linking, so no error emitted.
$ riscv64-unknown-elf-gcc -print-multi-directory -march=rv32ia -mabi=ilp32
.
// Link to default libc and libgcc, so check the multi-lib, and emit
// error because not found suitable multilib.
$ riscv64-unknown-elf-gcc -march=rv32ia -mabi=ilp32 ~/hello.c
riscv64-unknown-elf-gcc: fatal error: can't found suitable multilib set for '-march=rv32ia'/'-mabi=ilp32'
compilation terminated.
// No error emitted, because not link to stdlib.
$ riscv64-unknown-elf-gcc -march=rv32ia -mabi=ilp32 ~/hello.c -nostdlib
// No error emitted, because compile only.
$ riscv64-unknown-elf-gcc -march=rv32ia -mabi=ilp32 ~/hello.c -c
gcc/ChangeLog:
* common/config/riscv/riscv-common.c (riscv_subset_list::match_score):
New.
(find_last_appear_switch): Ditto.
(struct multi_lib_info_t): Ditto.
(riscv_no_matched_multi_lib): Ditto.
(riscv_current_arch_str): Ditto.
(riscv_current_abi_str): Ditto.
(riscv_compute_multilib): Ditto.
(TARGET_COMPUTE_MULTILIB): Defined.
* config/riscv/elf.h (LIB_SPEC): Call riscv_multi_lib_check if
doing link.
(RISCV_USE_CUSTOMISED_MULTI_LIB): New.
* config/riscv/riscv.h (riscv_multi_lib_check): New.
(EXTRA_SPEC_FUNCTIONS): Add riscv_multi_lib_check.
---
gcc/common/config/riscv/riscv-common.c | 253 +++++++++++++++++++++++++
gcc/config/riscv/elf.h | 6 +-
gcc/config/riscv/riscv.h | 4 +-
3 files changed, 261 insertions(+), 2 deletions(-)
diff --git a/gcc/common/config/riscv/riscv-common.c b/gcc/common/config/riscv/riscv-common.c
index 5e3ddcf3f81..481f0be9944 100644
--- a/gcc/common/config/riscv/riscv-common.c
+++ b/gcc/common/config/riscv/riscv-common.c
@@ -30,6 +30,7 @@ along with GCC; see the file COPYING3. If not see
#include "flags.h"
#include "diagnostic-core.h"
#include "config/riscv/riscv-protos.h"
+#include <vector>
#define RISCV_DONT_CARE_VERSION -1
@@ -171,12 +172,31 @@ public:
static riscv_subset_list *parse (const char *, location_t);
+ int match_score (riscv_subset_list *) const;
};
static const char *riscv_supported_std_ext (void);
static riscv_subset_list *current_subset_list = NULL;
+/* struct for recording multi-lib info. */
+struct riscv_multi_lib_info_t {
+ std::string path;
+ std::string arch_str;
+ std::string abi_str;
+ riscv_subset_list *subset_list;
+
+ static bool parse (struct riscv_multi_lib_info_t *,
+ const std::string &);
+};
+
+/* Flag for checking if there is no suitable multi-lib found. */
+static bool riscv_no_matched_multi_lib;
+
+/* Used for record value of -march and -mabi. */
+static std::string riscv_current_arch_str;
+static std::string riscv_current_abi_str;
+
riscv_subset_t::riscv_subset_t ()
: name (), major_version (0), minor_version (0), next (NULL),
explicit_version_p (false), implied_p (false)
@@ -202,6 +222,42 @@ riscv_subset_list::~riscv_subset_list ()
}
}
+/* Compute the match score of two arch string, return 0 if incompatible. */
+int
+riscv_subset_list::match_score (riscv_subset_list *list) const
+{
+ riscv_subset_t *s;
+ int score = 0;
+ bool has_a_ext, list_has_a_ext;
+
+ /* Impossible to match if XLEN is different. */
+ if (list->m_xlen != this->m_xlen)
+ return 0;
+
+ /* There is different code gen in libstdc++ and libatomic between w/ A-ext
+ and w/o A-ext, and it not work if using soft and hard atomic mechanism
+ at same time, so they are incompatible. */
+ has_a_ext = this->lookup ("a") != NULL;
+ list_has_a_ext = list->lookup ("a") != NULL;
+
+ if (has_a_ext != list_has_a_ext)
+ return 0;
+
+
+ /* list must be subset of current this list, otherwise it not safe to
+ link.
+ TODO: We might give different weigth for each extension, but the rule could
+ be complicated.
+ TODO: We might consider the version of each extension. */
+ for (s = list->m_head; s != NULL; s = s->next)
+ if (this->lookup (s->name.c_str ()) != NULL)
+ score++;
+ else
+ return 0;
+
+ return score;
+}
+
/* Get the rank for single-letter subsets, lower value meaning higher
priority. */
@@ -1109,6 +1165,203 @@ riscv_expand_arch_from_cpu (int argc ATTRIBUTE_UNUSED,
return xasprintf ("-march=%s", arch.c_str());
}
+static const char *
+find_last_appear_switch (
+ const struct switchstr *switches,
+ int n_switches,
+ const char *prefix)
+{
+ int i;
+ size_t len = strlen (prefix);
+
+ for (i = 0; i < n_switches; ++i) {
+ const struct switchstr *this_switch = &switches[n_switches - i - 1];
+
+ if (this_switch->live_cond & SWITCH_FALSE)
+ continue;
+
+ if (strncmp (this_switch->part1, prefix, len) == 0)
+ return this_switch->part1 + len;
+ }
+
+ return NULL;
+}
+
+bool
+riscv_multi_lib_info_t::parse (
+ struct riscv_multi_lib_info_t *multi_lib_info,
+ const std::string &path)
+{
+ if (path == ".")
+ {
+ multi_lib_info->arch_str = STRINGIZING (TARGET_RISCV_DEFAULT_ARCH);
+ multi_lib_info->abi_str = STRINGIZING (TARGET_RISCV_DEFAULT_ABI);
+ multi_lib_info->subset_list =
+ riscv_subset_list::parse(
+ STRINGIZING (TARGET_RISCV_DEFAULT_ARCH),
+ input_location);
+ }
+ else
+ {
+ size_t slash_pos = path.find('/');
+
+ if (slash_pos == std::string::npos)
+ return false;
+
+ multi_lib_info->arch_str = path.substr(0, slash_pos);
+ multi_lib_info->abi_str = path.substr(slash_pos + 1, path.length() - 1);
+ }
+
+ multi_lib_info->subset_list =
+ riscv_subset_list::parse(multi_lib_info->arch_str.c_str (), input_location);
+
+ return true;
+}
+
+const char *
+riscv_multi_lib_check (int argc ATTRIBUTE_UNUSED,
+ const char **argv ATTRIBUTE_UNUSED)
+{
+ if (riscv_no_matched_multi_lib)
+ fatal_error (
+ input_location,
+ "Can't found suitable multilib set for %<-march=%s%>/%<-mabi=%s%>",
+ riscv_current_arch_str.c_str (),
+ riscv_current_abi_str.c_str ());
+
+ return "";
+}
+
+/* We only override this in bare-matel toolchain. */
+#ifdef RISCV_USE_CUSTOMISED_MULTI_LIB
+/* Implement TARGET_COMPUTE_MULTILIB. */
+
+static const char *
+riscv_compute_multilib (
+ const struct switchstr *switches,
+ int n_switches,
+ const char *multilib_dir,
+ const char *multilib_defaults ATTRIBUTE_UNUSED,
+ const char *multilib_select,
+ const char *multilib_matches ATTRIBUTE_UNUSED,
+ const char *multilib_exclusions ATTRIBUTE_UNUSED,
+ const char *multilib_reuse ATTRIBUTE_UNUSED)
+{
+ const char *p;
+ const char *this_path;
+ size_t this_path_len;
+ bool result;
+ riscv_no_matched_multi_lib = false;
+ riscv_subset_list *subset_list = NULL;
+
+ std::vector<riscv_multi_lib_info_t> multilib_infos;
+ riscv_multi_lib_info_t multilib_info;
+
+ /* Already found suitable, multi-lib, just use that. */
+ if (multilib_dir != NULL)
+ return multilib_dir;
+
+ /* Find last march. */
+ riscv_current_arch_str =
+ find_last_appear_switch (switches, n_switches, "march=");
+ /* Find mabi. */
+ riscv_current_abi_str =
+ find_last_appear_switch (switches, n_switches, "mabi=");
+
+ /* Failed to find -march or -mabi, but it should not happened since we have
+ set both in OPTION_DEFAULT_SPECS. */
+ if (riscv_current_arch_str.empty () || riscv_current_abi_str.empty ())
+ return multilib_dir;
+
+ subset_list = riscv_subset_list::parse (riscv_current_arch_str.c_str (),
+ input_location);
+
+ /* Failed to parse -march, fallback to using what gcc use. */
+ if (subset_list == NULL)
+ return multilib_dir;
+
+ /* Parsing MULTILIB_SELECT, ignore MULTILIB_REUSE here, we have our own rules.
+ TODO: most codes are grab from gcc.c, maybe we should refine that? */
+ p = multilib_select;
+
+ while (*p != '\0')
+ {
+ /* Ignore newlines. */
+ if (*p == '\n')
+ {
+ ++p;
+ continue;
+ }
+
+ /* Get the initial path. */
+ this_path = p;
+ while (*p != ' ')
+ {
+ if (*p == '\0')
+ {
+ fatal_error (input_location, "multilib select %qs %qs is invalid",
+ multilib_select, multilib_reuse);
+ }
+ ++p;
+ }
+ this_path_len = p - this_path;
+ multilib_info.path = std::string (this_path, this_path_len);
+
+ while (*p != ';')
+ {
+ if (*p == '\0')
+ {
+ fatal_error (input_location, "multilib select %qs %qs is invalid",
+ multilib_select, multilib_reuse);
+ }
+ ++p;
+ }
+
+ result =
+ riscv_multi_lib_info_t::parse (
+ &multilib_info,
+ std::string (this_path, this_path_len));
+
+ if (result)
+ multilib_infos.push_back (multilib_info);
+
+ p++;
+ }
+
+ int match_score = 0;
+ int max_match_score = 0;
+ int best_match_multi_lib = -1;
+ /* Try to decition which set we should used. */
+ /* We have 3 level dection tree here, ABI, A-ext, check input arch/ABI must be
+ superset of multi-lib arch. */
+ for (size_t i = 0; i < multilib_infos.size (); ++i)
+ {
+ /* Check ABI is same first. */
+ if (riscv_current_abi_str != multilib_infos[i].abi_str)
+ continue;
+
+ /* Found a potential compatible multi-lib setting!
+ Calculate the match score. */
+ match_score = subset_list->match_score (multilib_infos[i].subset_list);
+
+ /* Record highest match score multi-lib setting. */
+ if (match_score > max_match_score)
+ best_match_multi_lib = i;
+ }
+
+ if (best_match_multi_lib == -1)
+ {
+ riscv_no_matched_multi_lib = true;
+ return multilib_dir;
+ }
+ else
+ return xstrdup (multilib_infos[best_match_multi_lib].path.c_str ());
+}
+
+#undef TARGET_COMPUTE_MULTILIB
+#define TARGET_COMPUTE_MULTILIB riscv_compute_multilib
+#endif
+
/* Implement TARGET_OPTION_OPTIMIZATION_TABLE. */
static const struct default_options riscv_option_optimization_table[] =
diff --git a/gcc/config/riscv/elf.h b/gcc/config/riscv/elf.h
index 4e2d6464d02..4aeb7d6141c 100644
--- a/gcc/config/riscv/elf.h
+++ b/gcc/config/riscv/elf.h
@@ -25,10 +25,14 @@ along with GCC; see the file COPYING3. If not see
/* Link against Newlib libraries, because the ELF backend assumes Newlib.
Handle the circular dependence between libc and libgloss. */
#undef LIB_SPEC
-#define LIB_SPEC "--start-group -lc %{!specs=nosys.specs:-lgloss} --end-group"
+#define LIB_SPEC \
+ "--start-group -lc %{!specs=nosys.specs:-lgloss} --end-group " \
+ "%{!nostartfiles:%{!nodefaultlibs:%{!nolibc:%{!nostdlib:%:riscv_multi_lib_check()}}}}"
#undef STARTFILE_SPEC
#define STARTFILE_SPEC "crt0%O%s crtbegin%O%s"
#undef ENDFILE_SPEC
#define ENDFILE_SPEC "crtend%O%s"
+
+#define RISCV_USE_CUSTOMISED_MULTI_LIB 1
diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h
index df3003fbaa0..a92e0e220ad 100644
--- a/gcc/config/riscv/riscv.h
+++ b/gcc/config/riscv/riscv.h
@@ -43,11 +43,13 @@ 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_multi_lib_check (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_multi_lib_check", riscv_multi_lib_check },
/* Support for a compile-time default CPU, et cetera. The rules are:
--with-arch is ignored if -march or -mcpu is specified.
--
2.29.2
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